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Purpose: To compare the effects of variable-resistance complex training (VRCT) versus traditional complex training (TCT) on strength, power, speed, and leg stiffness (Kleg) in rugby league players during a 6-week mesocycle. Methods: Twenty-four rugby league players competing in the British University and Colleges Sport Premier North Division were randomized to VRCT (n = 8), TCT (n = 8), or control (CON; n = 8). Experimental groups completed a 6-week lower-body complex training intervention (2×/wk) that involved alternating high-load resistance exercise with plyometric exercise within the same session. The VRCT group performed resistance exercises at 70% of 1-repetition maximum (1RM) + 0% to 23% of 1RM from band resistance with a 90-second intracontrast rest interval, whereas the TCT group performed resistance exercise at 93% of 1RM with a 4-minute intracontrast rest interval. Back-squat 1RM, countermovement jump peak power, reactive strength index, sprint times, and Kleg were assessed pretraining and posttraining. Results: VRCT and TCT significantly improved 1RM back squat, countermovement jump peak power, and 5-m sprint time (all P leg, whereas TCT improved 10- and 20-m sprint times (all P P leg compared with CON (right leg: P = .016) and TCT improved 20-m sprint time compared with CON (P = .042). Conclusions: VRCT and TCT can be implemented during the competitive season to improve strength, power, and 5-m sprint time. VRCT may lead to greater improvements in reactive strength index and Kleg, whereas TCT may enhance 10- and 20-m sprint times.

This study aims to determine the propulsive force (F

External Counterpulsation (ECP) is a well-established treatment for coronary disease, with interest growing in the potential to act as a sports recovery modality or pre-performance strategy. This pilot study compared the effects of different ECP durations upon neuromuscular function (NF), cortisol and subjective perceptions in a rested state. Eleven physically active male volunteers received two ECP treatments (Renew Sport, Singapore) of differing duration (20-min and 40-min) in a randomised, repeated measures crossover design. Testing occurred pre-ECP, post-ECP, and 24-h post-ECP. NF testing comprised counter-movement jumps (CMJs) and 6-s sprint cycling. Saliva samples were analysed for cortisol. Rate of Perceived Exertion (RPE, 6 to 20) and Bipolar Comfort Scales (− 10 to 10) quantified participants’ experiences, and ECP duration preference was examined. Repeated measures ANOVA and effect size (ES: Cohen’s d) analysed NF and cortisol results. Paired t-tests analysed RPE and comfort ratings. ECP demonstrated no effect, neither positive nor negative, upon NF outcome measures in both groups. A trend of reduced salivary cortisol levels across both groups following ECP was observed (P = 0.066). No RPE difference existed between groups. 20-min of ECP was rated as significantly more comfortable than 40-min (P

Age-related impairments in motor performance are caused by a deterioration in mechanical and neuromuscular functions, which have been investigated from the macro-level of muscle-tendon unit to the micro-level of the single muscle fiber. When compared to the healthy young skeletal muscle, aged skeletal muscle is: (1) weaker, slower and less powerful during the performance of voluntary contractions; (2) less steady during the performance of isometric contractions, particularly at low levels of force; and (3) less susceptible to fatigue during the performance of sustained isometric contractions, but more susceptible to fatigue during the performance of high-velocity dynamic contractions. These impairments have been discussed to be mainly the result of: a) loss of muscle mass and selective atrophy of type II muscle fibers; b) altered tendon mechanical properties (decreased tendon stiffness); c) reduced number and altered function of motor units; d) slower muscle fiber shortening velocity; e) increased oscillation in common synaptic input to motor neurons; and f) altered properties and activity of sarcoplasmic reticulum. In this second part of a two-part review we have detailed the age-related impairments in motor performance with a reference to the most important mechanical and neuromuscular contributing factors.

Ultra Short Race Pace training (USRPT) is an emerging training modality devised in 2011 to deviate from high-volume swimming training that is typically prescribed. USRPT aims to replicate the exact demands of racing, through its unique prescription of race-pace velocity sets with short rest intervals. It has been surmised, with little physiological evidence, that USRPT provides swimmers with the best opportunity to optimize the conditioning, technique, and psychology aspects of racing at the most specific velocity of the relevant event, with low blood lactate concentration. The aim of this study was to examine acute physiological responses of USRPT. Fourteen swimmers were recruited to perform a USRPT set: 20 x 25 m freestyle with a 35-s rest interval. Swimmers were required to maintain the velocity of their 100 m personal best time for each sprint. Sprint performance, blood lactate, heart rate and the RPE were measured. Blood lactate was taken before, during (after every 4 sprints) and 3 minutes after the USRPT protocol. Heart rate monitors were used to profile the heart rate. Athletes reported the RPE before- and after completion of the USRPT set. Sprint times increased by 3.3-10.8% when compared to the first sprint (p < 0.01). There was high blood lactate concentration (13.6 ± 3.1mmol/l), a significant change in the RPE from 8 ± 1.6 to 18 ± 1.6 (p < 0.01) and a substantially high heart rate profile with an average HRmax of 188 ± 9 BPM. The results show the maximal intensity nature of USRPT and portray it as an anaerobic style of training.

Purpose: To compare the effects of variable-resistance complex training (VRCT) versus traditional complex training (TCT) on muscle architecture in rugby league players during a 6-week mesocycle. Methods: Twenty-four rugby league players competing in the British University & Colleges Sport (BUCS) Premier North Division were randomized to VRCT (n = 8), TCT (n = 8), or control (n = 8). Experimental groups completed a 6-week lower-body complex training intervention (2×/wk), which involved alternating high-load resistance exercise with plyometric exercise in the same session. The VRCT group performed resistance exercises at 70% of 1-repetition maximum (1RM) + 0% to 23% of 1RM from band resistance with a 90-second intracontrast rest interval, whereas the TCT group performed resistance exercise at 93% of 1RM with a 4-minute intracontrast rest interval. Muscle thickness (MT), pennation angle, and fascicle length (Lf) were assessed for the vastus lateralis (VL) and gastrocnemius medialis using ultrasound imaging. Results: Both TCT and VRCT groups significantly improved VL MT and VL Lf compared with control (all P Lf (Cohen dav ± 95% CI) were moderate for TCT (dav = 0.91 ± 1.0; dav = 1.1 ± 1.1) and unclear for VRCT (dav = 0.44 ± 0.99; dav = 0.47 ± 0.99), respectively. Differences in change scores between TCT and VRCT were unclear. Conclusions: VRCT and TCT can be utilized during the competitive season to induce favorable MT and Lf muscle architecture adaptations for the VL. TCT may induce greater muscle architecture adaptations of the VL, whereas VRCT may be of more practical value given the shorter intracontrast rest interval between resistance and plyometric exercises.

Objectives: To assess the magnitude of change and association with variation in training load of two performance markers and wellbeing, over three pre-season training blocks, in elite rugby union athletes. Design: Observational. Methods: Twenty-two professional players (age 25 ± 5 years; training age 6 ± 5 years; body mass, 99 ± 13 kg; stature 186 ± 6 cm) participated in this study, with changes in lower (CMJ height) and upper body (bench press mean speed) neuromuscular function and self-reported wellbeing (WB) assessed during an 11-week period. Results: There was a small increase in CMJ height (0.27, ±0.17 – likely substantial; standardised effect size, ±95% confidence limits – magnitude-based inference) (p = 0.003), bench press speed (0.26, ±0.15 – likely substantial) (p = 0.001) and WB (0.26, ±0.12 – possibly substantial) (p < 0.0001) across the pre-season period. There was a substantial interaction in the effect of training load on these three variables across the three training phases. A two-standard deviation (2SD) change in training load was associated with: a small decrease in CMJ height during the power phase (−0.32, ±0.19 – likely substantial) (p = 0.001); a small reduction in bench press speed during the hypertrophy phase (−0.40, ±0.32 – likely substantial) (p = 0.02); and a small reduction in WB during the strength phase (−0.40, ±0.24 – very likely substantial) (p < 0.0001). The effects of changes in training load across other phases were either likely trivial, only possibly substantial, or unclear. Conclusions: The effect of training load on performance can vary both according to the type of training stimulus being administered and based on whether upper- or lower-body outcomes are being measured.

Intermittent exercise might be an efficient means of exercise for improving bone strength and quality. The aim of our study was to examine the effect of intermittent running on bone turnover markers using altered exercise-to-rest intervals. Twelve males completed one control (no exercise), and three, 45-min intermittent protocols (5, 20, and 80 s intervals) matched for distance and speed. Fasted venous blood samples were collected at baseline, 1, 2 and 24 h post-exercise. Carboxyterminal crosslinked telopeptide (CTX-I) and procollagen type 1 amino-terminal propeptide (P1NP) were used as markers of bone resorption and formation. After adjustment for baseline, CTX-I concentration at 1 h was higher (very likely to most likely small) for 5 s (30.2%; ±90% confidence limits: 10%), 20 s (2.9.0%; ±10%) and 80 s (32.0%; ±10%) compared to control. The very likely small effect remained for 5 s at 2 h (30.2%; ±15%). The effect for 20 and 80 s was possibly trivial and possibly small/possibly trivial (∼14.5%; ±∼15%). Differences in P1NP concentrations were likely to very likely trivial (∼7.4%; ±∼7.6%). Circulating CTX-I concentration is affected acutely by intermittent running with short-interval (5 s) intermittent loading resulting in a prolonged attenuation in circadian rhythm of CTX-I up to 2 h that was not demonstrated as clearly by longer intervals despite matched internal and external training load.

This study investigated the effect of knee joint angle and age on torque steadiness of knee extensors (KE) at varying submaximal isometric contractions.22 young (24.0 ± 2.6 years; 11 women) and 22 older (69.4 ± 2.4 years; 10 women) healthy men and women participated. Maximal voluntary isometric contraction (MVIC) of the KE and flexors was examined at 90° and 60° of knee flexion (0° = full extension). At each angle, participants performed KE isometric contractions (20%, 50% and 80% MVIC) to evaluate torque steadiness, whereas surface EMG was concurrently acquired from the vastus lateralis and biceps femoris muscles.Age-related impairment in torque steadiness was observed only at 20% MVIC (p 0.01). A lower level of steadiness (p 0.001) with a higher level of agonist and antagonist activations (all p 0.01) was observed at 90° of knee flexion in comparison with contractions at 60°. Young participants were less steady when performing contractions at 90° compared with contractions at 60° of flexion (p 0.001), whereas there was no difference for older participants. Furthermore, a significant effect of agonist activation and antagonist co-activation on torque steadiness was observed, but only in young participants (all p 0.05).These findings suggest that: (1) knee joint angle affects torque steadiness differently in young and older individuals; (2) an age-related impairment in steadiness was only presented at the lowest considered contraction intensity; and (3) the muscle activation responses were not associated with steadiness in older individuals.

External counterpulsation (ECP), an electrocardiogram-led sequential compression of lower limbs, has been recently proposed for sports recovery, but research is scant. This study examined the effects of an ECP session upon neuromuscular function (vertical jump and torque/velocity characteristics), biochemical responses (creatine kinase, cortisol, testosterone, alpha-amylase and immunoglobulin-A), and muscle soreness (visual analogue scale) following high-intensity exercise. Twenty-one male team sport athletes (age: 21.6±3.4 yrs; height: 182.7±7.3 cm; body mass: 82.7±9.3 kg) recovered from the fatiguing exercise using either ECP or rest. Data collection was conducted at three separate time points: upon arrival (Pre), post-recovery (Post), and 24 h post-recovery (24hPost). Significant main effects for time were observed for increased torque/velocity slope and for decreased isometric extension peak torque (p

BACKGROUND Loss of balance control is commonly experienced by older individuals. Despite the large amount of research on the effects of exercise on balance the optimal exercise regime is yet to be identified. Most studies have concentrated on strength training due to associations between muscle weakness, balance disfunction and fall risk. The effects of gross-motor skill exercise for balance and postural control have been less investigated. The study aimed to compare the effectiveness of strength training (STT) and gross-motor skill exercise (GMT) on static postural control, dynamic functional balance and strength in healthy older individuals. METHODS Thirty-eight individuals (65-85 years) participated to GMT or STT for 12 weeks, twice weekly. They were tested pre- and post-training for postural control (Romberg and Tandem positions on a force platform), dynamic functional balance (maximal walking speed in balance-challenging conditions), maximal isometric handgrip strength, maximal knee flexor and extensor strength. RESULTS Improvements were observed in static postural balance (tandem position, P

This two-part narrative review aims to provide an insight into the age-related mechanical and neuromuscular factors contributing to: (1) decreased maximal muscle strength and power; (2) decreased force control; and (3) increased fatigability. Structural and functional changes from the macro-level of the muscle-tendon unit to the micro-level of the single muscle fibre have been reviewed and are described. At the muscle-tendon unit level, muscle volume, thickness and cross-sectional area, as well as pennation angle and fascicle length all decrease as part of the natural ageing process. These changes negatively affect muscle quality, muscle and tendon stiffness and Young’s modulus and account for impairment in motor performance. A progressive age-related alteration in neuromuscular function is also well-established, with reduction in number and firing rate of the motor unit, contractile velocity and specific tension of muscle fibres, and stability of neuromuscular junction. These could be the result of structural alterations in the: (i) motor neuron, with number reduced, size and collateral sprouting increased; (ii) neuromuscular junction, with decreased post-synaptic junctional fold and density of active zones and increased pre-synaptic branching and post-synaptic area; and (iii) muscle fibre, with decreased number and size and increased type I and co-expression of myosin heavy chain.

To examine the effect of acute quercetin (Q) ingestion on neuromuscular function, biomarkers of muscle damage, and rate of perceived exertion (RPE) in response to an acute bout of resistance training. 10 young men (22.1 ± 1.8 years, 24.1 ± 3.1 BMI) participated in a randomized, double-blind, crossover study. Subjects consumed Q (1 g/day) or placebo (PLA) 3 h prior to a resistance training session which consisted of 3 sets of 8 repetitions at 80% of the one repetition maximum (1RM) completed bilaterally for eight different resistance exercises. Electromyographic (EMG) signals were recorded from the knee extensor muscles during maximal isometric (MVIC) and isokinetic voluntary contractions, and during an isometric fatiguing test. Mechanical and EMG signals, biomarkers of cell damage, and RPE score were measured PRE, immediately POST, and 24 h (blood indices only) following the resistance exercise. After a single dose of Q, the torque–velocity curve of knee extensors was enhanced and after the resistance exercise, subjects showed a lower MVIC reduction (Q: 0.91 ± 6.10%, PLA: 8.66 ± 5.08%) with a greater rate of torque development (+ 10.6%, p

Skeletal muscle operates as a near-constant volume system; as such muscle shortening during contraction is transversely linked to radial deformation. Therefore, to assess contractile properties of skeletal muscle, radial displacement can be evoked and measured. Mechanomyography measures muscle radial displacement and during the last 20 years, tensiomyography has become the most commonly used and widely reported technique among the various methodologies of mechanomyography. Tensiomyography has been demonstrated to reliably measure peak radial displacement during evoked muscle twitch, as well as muscle twitch speed. A number of parameters can be extracted from the tensiomyography displacement/time curve and the most commonly used and reliable appear to be peak radial displacement and contraction time. The latter has been described as a valid non-invasive means of characterising skeletal muscle, based on fibre-type composition. Over recent years, applications of tensiomyography measurement within sport and exercise have appeared, with applications relating to injury, recovery and performance. Within the present review, we evaluate the perceived strengths and weaknesses of tensiomyography with regard to its efficacy within applied sports medicine settings. We also highlight future tensiomyography areas that require further investigation. Therefore, the purpose of this review is to critically examine the existing evidence surrounding tensiomyography as a tool within the field of sports medicine.

This study examined trunk muscle activation, balance and proprioception while squatting with a water-filled training tube (WT) and a traditional barbell (BB), with either closed (CE) or open eyes (OE). Eighteen male elite Gaelic footballers performed an isometric squat under the following conditions: BB-OE, BB-CE, WT-OE and WT-CE. The activity of rectus abdominis (RA), external oblique (EO) and multifidus (MF) was measured using electromyography, along with sway of the centre of pressure (CoP) using a force platform. Only the EO and the MF muscles exhibited an increased activity with WT (p 0.01). In the medio-lateral direction both the velocity and range of the CoP increased significantly with WT (p 0.01). Interestingly, the range of the CoP for the WT-CE condition was significantly lower than WT-OE (p 0.05, d = 0.44), whilst the velocity of the CoP was marginally reduced (d = 0.29). WT elicited a greater level core muscle activation and created a greater challenge to postural stability when compared to a BB. It appears that WT does not benefit from vision but emphasises the somatosensory control of balance. The use of WT may be beneficial in those sports requiring development of somatosensory/proprioceptive contribution to balance control.

BACKGROUND: Intermittent mechanical loading generates greater bone adaptations than continuous mechanical loading in rodents but has never been evaluated in humans. This study aimed to evaluate the feasibility of a continuous and intermittent countermovement jump (CMJ) intervention for attenuating early postmenopausal BMD loss. \ud METHODS: 41 healthy early postmenopausal women (age = 54.6 ± 3.4 years) were randomly assigned to a continuous countermovement jumping group, an intermittent countermovement jumping group or a control group for 12 months. Adherence and dropout rates were recorded along with bone mineral density (BMD) at lumbar spine, femoral neck and trochanter sites at baseline, 6 months and 12 months.\ud RESULTS: 28 participants completed the study. Dropout rate during the intervention (from the initiation of exercise) was 36% from continuous and 38% from intermittent countermovement jumping groups. For the participants that completed the intervention, adherence was 60.0 ± 46.8% for continuous and 68.5 ± 32.3% for intermittent countermovement jumping. The control group lost significant lumbar spine BMD (% difference = -2.7 [95%CI: -3.9 to -1.4]) and femoral neck BMD (% difference = -3.0% [95%CI: -5.1 to -0.8]). There was no statistically significant change in BMD for either countermovement jumping group. There was no statistically significant difference in BMD change between continuous or intermittent countermovement jumping groups when compared with the control group.\ud CONCLUSIONS: Adherence and dropout rates were in line with previous similar interventions. To evaluate the effect of continuous and intermittent exercise on BMD, future studies should focus on maintaining participant engagement and adherence to the exercise intervention.

Given their functional role and importance, the activity of several trunk muscles was assessed (via surface electromyography-EMG) during Walking (W) and Pole Walking (PW) in 21 healthy adults. EMG data was collected from the external oblique (EO), the erector spinae longissimus (ES), the multifidus (MU), and the rectus abdominis (RA) while performing W and PW on a motorized treadmill at different speeds (60, 80, and 100% of the highest speed at which the participants still walked naturally; PTS60, PTS80 and PTS100, respectively) and grades (0 and 7%; GRADE0 and GRADE7, respectively). Stride length, EMG area under the curve (AUC), muscles activity duration (ACT), and percentage of coactivation (CO-ACT) of ES, MU and RA, were calculated from the averaged stride for each of the tested combinations. Compared to W, PW significantly increased the stride length, EOAUC, RAAUC and the activation time of all the investigated muscles, to different extents depending on treadmill speeds and grades. In addition, MUAUC was higher in PW than in W at GRADE0 only (all speeds, p

Muscle activation, peak velocity (PV) and perceived technical difficulty while using three grip variations and three loads during a deadlift exercise (DL) were examined. Twenty-nine resistance-trained athletes (15 males, age: 22.2 ± 2.7 years; 14 females, age: 24.8 ± 7.0 years) performed the DL with 50%, 70% and 90% of their one repetition maximum (1RM) using hook grip (HG), mixed grip (MG) and double overhand (DOH) grip. Surface electromyography (EMG) of the brachialis (BS), brachioradialis (BR) and flexor carpi ulnaris (FCU) was recorded. PV and perceived technical difficulty of each grip were also measured. Regardless of load and grip, females exhibited greater BS activation compared to males (p 0.05; ES = 0.69) while males displayed greater BR activation, significant at 90% load (p 0.01; ES = 1.01). MG elicited the least BR and FCU activation regardless of load and sex (p 0.01; ES = 0.64-0.68) and was consistently ranked as the easiest grip for any load. Males achieved significantly greater PV than females at 50% and 70% (p 0.01; ES = 1.72-1.92). Hand orientation did not significantly impact PV. A MG may be beneficial in reducing the overall perceived technical difficulty when performing a maximal DL. Athletes aiming to maximise muscle activation and potentially develop their grip strength should utilise a DOH grip or HG.

The purpose of this study was to investigate the age-related alterations in the ability to exert maximal and to sustain submaximal isometric muscle torques after a fatiguing concentric exercise conducted with knee extensor (KE) and flexor (KF) muscles. Sixteen young (aged 19-30 years; 8 women) and 17 older (aged 65-75 years; 9 women) volunteers participated. The following tasks were performed before and immediately after 22 maximal concentric efforts of the right KE and KF at 1.05 rad/s: (1) a maximal voluntary isometric contraction (MVIC) task involving both KE and KF; and (2) a KE torque-steadiness task at a submaximal target contraction intensity (20% MVIC). During the dynamometric tests, surface EMG was recorded simultaneously from the KE and KF muscles. Fatigue-induced reductions in knee extension MVIC were similar (~15%) between groups, but young participants showed more pronounced declines in agonist (i.e. quadriceps) EMG responses in both time (RMS amplitude; ~15% vs. ~10%, p 0.001) and frequency (median frequency; ~14% vs. ~8%, p 0.01) domains. Torque steadiness exhibited a similar post-fatigue decrease in the two age groups (p 0.01), but interestingly agonist activation (~17%; p 0.001) and antagonist (i.e. hamstrings) co-activation (~16%; p 0.001) declined only in the older participants. These findings suggest that the fatiguing concentric KE and KF exercise results in similar relative reductions (%) in maximal torque and steadiness of the KE in young and older individuals, but they are sustained by different age-related neuromuscular strategies.

High impact exercise can reduce postmenopausal bone loss, however stimulus frequency (loading cycles per second) can affect osteogenesis. We aimed to examine the effect of stimulus frequency on the mechanical loading of four common osteoporosis prevention exercises, measuring body acceleration and muscle activation with accelerometry and electromyography (EMG), respectively. Fourteen early postmenopausal women completed randomised countermovement jumps (CMJ), boxdrops (BD), heel-drops (HD) and stamp (STP) exercises for continuous and intermittent stimulus frequencies. Sacrum accelerometry and surface electromyography (EMG) of four muscles were recorded. CMJ (mean ± SD: 10.7 ± 4.8 g & 10.0 ± 5.0 g), BD (9.6 ± 4.1 g & 9.5 ± 4.0 g) and HD (7.3 ± 3.8 g & 8.6 ± 4.4 g) conditions generated greater peak acceleration than STP (3.5 ± 1.4 g & 3.6 ± 1.7 g) across continuous and intermittent trials. CMJ and BD generated greater acceleration gradients than STP across continuous and intermittent trials. CMJ generated greater rectus femoris EMG than all other exercises, CMJ and BD generated\ud greater semitendinosus and tibialis anterior EMG than HD across continuous and intermittent trials. CMJ and BD provide greater peak acceleration than STP and remain similar during different stimulus frequencies. CMJ, BD and HD may exceed STP in maintaining postmenopausal bone health

Purpose: The well-being of elite rugby union players has been intensely scrutinised in recent years. Understanding the longitudinal development of physical traits in junior players, alongside the moderating effect of simultaneous increases in body mass, can aid in improving programming and ultimately help junior players prepare for the demands of senior rugby. The purpose of this study was to investigate the longitudinal physical development of elite adolescent backs and forwards in a professional rugby union academy. Methods: A total of 15 players (age, 17.0 [0.2] y; body mass, 90 [14] kg; height, 183 [9] cm; n = 7 backs, n = 8 forwards) completed anthropometric measures and 3 primary performance assessments (countermovement jump, Yo-Yo intermittent recovery test level 1, and 10-m speed) at baseline, year 2, and year 3. Mixed modelling was used to assess player development over time and differences in this development by playing position. Magnitude-based inferencing was used to assess the uncertainty in the effects. Results: There was a substantial increase in countermovement jump height for both groups combined (0.9, ±0.4; standardized improvement, ±90% confidence limits; most likely substantial). Forwards exhibited a moderate-sized decrease in speed (−1.0, ±0.5; very likely substantial), and there was a large difference between groups with regards to speed change with backs outperforming forwards (1.5, ±0.9; very likely substantial). For forward, body mass change had a large negative association with 10-m speed (−1.9, ±0.7; most likely substantial) and Yo-Yo intermittent recovery test level 1 change (−1.2, ±0.9; very likely substantial). Conclusion: These findings provide novel normative data for longitudinal changes in junior rugby union players and suggest that coaches should account for changes in body mass when targeting increases in speed and aerobic fitness.

© 2018 Sporri et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Since higher vertical stiffness is related to superior athletic performance, training has traditionally been aimed at augmenting this variable to enhance neuromuscular output. However, research has linked elevated stiffness with increased injury risk, therefore, this study examined the effect of a novel training intervention on vertical stiffness and athletic performance. Vertical stiffness, jump performance and athletic performance were assessed in two randomly allocated groups, prior to, and following, an eight-week period. One group was exposed to a training intervention involving aqua-based plyometrics (n = 11) over the 8 weeks while the other acted as a control group (n = 9). The training intervention involved hopping, jumping and bounding in water at a depth of 1.2m whilst control participants performed their normal training. There were no significant changes in vertical stiffness in either group. Countermovement jump height and peak power significantly increased within the aqua plyometric group (p < 0.05). Athletic performance markers improved in the aqua plyometric group as measured using an agility and a 5-bound test exhibiting superior values at the post-test (p < 0.05). The results suggest that an aqua plyometric training program can enhance athletic performance without elevating stiffness. The increase in athletic performance is likely due to a reduction in ground reaction forces created by the buoyancy of the water, causing a shorter amortization phase and a more rapid application of concentric force. The findings from this study can inform exercise professionals and medical staff regarding the ability to enhance neuromuscular performance without elevating vertical stiffness. This has implications for improving athletic performance while concurrently minimising injury risk.

Purpose: Resisted sled sprinting (RSS) is an effective tool for improving sprint performance over short distances, but the effect on change-of-direction (COD) performance is largely unknown. The present study investigated the effect of heavy RSS training during the competitive season on sprint and COD performance in professional soccer players. Methods: Over 6 wk in-season, an RSS training group (n = 6) performed RSS at a sled load of 30% body mass for a total program running distance of 800 m, whereas an unresisted sprint (URS) training group (n = 7) performed the same distance of unresisted sprinting. A 20-m maximal sprint with split times measured at 5, 10, and 20 m and the sprint 9-3-6-3-9 m with 180° turns COD test were performed before and after the intervention. Results: Sprint performance (mean, 95% confidence limits, qualitative inference) was improved in both groups over 5 m (URS, 5.1%, −2.4 to 12.7, likely moderate; RSS, 5.4%, 0.5–10.4, likely moderate), 10 m (URS, 3.9%, −0.3 to 8.1, very likely moderate; RSS, 5.0%, 1.8–8.0, very likely large), and 20 m (URS, 2.0%, −0.6 to 4.5, likely moderate; RSS, 3.0%, 1.7–4.4, very likely moderate). COD was improved in both groups (URS, 3.7%, 2.2–5.2, most likely large; RSS, 3.3%, 1.6–5.0, most likely moderate). Between-groups differences were unclear. Conclusion: Heavy RSS and URS training matched for running distance were similarly effective at improving sprint and COD performance in professional soccer players when performed in the competitive phase of the season.

Musculo-articular stiffness (MAS) of the triceps surae can be assessed using the free-oscillation technique whereby an impulse is applied and the ensuing damped oscillations are recorded. The purpose of this study was to investigate if impulses of different magnitudes can affect the measurement of MAS. Twenty seven males (20.7±1.3 years) participated in this study. Three impulses of different magnitude (1.5, 2.3 and 3.1Ns) and four different loads (10, 20, 30, 40kg) were employed in the assessment of triceps surae MAS, which was quantified and compared across loads and perturbations. As the magnitude of the impulse applied increased, the MAS (p

The objective of this study was to investigate the gender-specific differences in peak torque (PT), muscle stiffness (MS) and musculoarticular stiffness (MAS) of the knee joints in a young active population. Twenty-two male and twenty-two female recreational athletes participated. PT of the knee joint extensor musculature was assessed on an isokinetic dynamometer, MS of the vastus lateralis (VL) muscle was measured in both relaxed and contracted conditions, and knee joint MAS was quantified using the free oscillation technique. Significant gender differences were observed for all dependent variables. Females demonstrated less normalized PT (mean difference (MD)=0.4Nm/kg, p =0.005, η 2 =0.17), relaxed MS (MD=94.2N/m, p η 2 =0.53), contracted MS (MD=162.7N/m, p η 2 =0.53) and MAS (MD=422.1N/m, p η 2 =0.23) than males. MAS increased linearly with the external load in both genders with males demonstrating a significantly higher slope ( p =0.019) than females. The observed differences outlined above may contribute to the higher knee joint injury incidence and prevalence in females when compared to males.

Hamstring injuries are common in field sport athletes. Eccentric strength training of the hamstring muscles is an integral component of rehabilitation programs. The Askling L-Protocol comprises three exercises [extender; diver; glider] that load the hamstrings during eccentric activity. When compared to a conventional exercise-based rehabilitation program, the Askling L-Protocol has been shown to reduce the time to return to sport following hamstring injury and prevalence of injury recurrence. Nevertheless, the mechanisms behind its efficacy have yet to be studied. In this work, we conducted a kinematic and electromyographic analysis of the exercises of the Askling L-Protocol. Eleven healthy individuals performed each of the exercises while electromyographic data from four muscles (including two hamstring muscles) were recorded. Hip and knee angular displacements and velocities were also synchronously recorded using a motion capture system. We found that the L-Protocol elicits a maximal contraction (up to 60% of the MVC in the glider exercise) in the hamstring muscles at a work point similar to the swing phase of running (around 62 degrees hip flexion and 23 degrees knee flexion). No difference in the levels of activation of the hamstrings was observed between the diver and glider, regardless of the different functional role they had in the two exercises. During the extender, the hamstring muscles are stretched and minimally engaged. Finally, co-activation analysis highlighted that through the combination of passive stretch and active eccentric contraction, the hamstrings are trained to co-activate using similar structural modules employed differentially to drive the movement or stabilize it.

Scott, DJ, Ditroilo, M, and Marshall, P. Effect of accommodating resistance on the post-activation potentiation response in rugby league players. J Strength Cond Res 32(9): 2510-2520, 2018-This study examined the postactivation potentiation (PAP) response of 2 conditioning activities (CA), the hex bar deadlift and back squat, combined with accommodating resistance; this adds a percentage of the total resistance during the exercise. Twenty amateur rugby league players performed 2 experimental trials and a control trial without a CA. Participants performed a countermovement jump (CMJ) before and 30, 90, and 180 seconds after 1 set of 3 repetitions of each CA at 70% 1 repetition maximum (RM), with up to an additional 23% 1RM from accommodating resistance. Peak power output (PPO), force at PPO, velocity at PPO, and jump height were calculated for each CMJ. Surface electromyography (EMG) of the vastus lateralis (VL), rectus femoris (BF), tibialis anterior (TA), and gastrocnemius medialis (GM) was also measured. Repeated-measures analysis of variance revealed no significant (p > 0.05) PAP response for either exercise condition when comparing CMJ variables with baseline values nor were there any significant (p > 0.05) differences between exercise conditions. However, individualized recovery intervals (baseline vs. maximum potentiation response) demonstrated significant (p ≤ 0.05) improvements in PPO (3.99 ± 4.99%), force at PPO (4.87 ± 6.41%), velocity at PPO (4.30 ± 5.86%), jump height (8.45 ± 10.08%), VL EMG (20.37 ± 34.48%), BF EMG (22.67 ± 27.98%), TA EMG (21.96 ± 37.76%), and GM EMG (21.89 ± 19.65%). Results from this study must be interpreted with caution; however, it is conceivable that athletic performance can be acutely enhanced when complex training variables are individualized.

Purpose: The main purpose of this study was to investigate the influence of fatigue on musculoarticular stiffness (MAS) of the ankle joint across sexes. Methods: Twenty-seven males and 26 females participated in the study. After baseline assessment of MAS and related variables, localised fatigue was induced in triceps surae using the standing heel-rise test during which the subjects were instructed to lift and drop the heel at a frequency of 0.5 Hz. When subjects were unable to continue due to exhaustion the test was terminated and another MAS test was performed soon after. Results: Significant higher triceps surae MAS was found in men compared to women (p .01) between sexes, with MAS less than 5%. Conclusion: Despite the sex-related differences at baseline, fatigue seems to affect biomechanical properties of the ankle joint similarly in men and women.

This study compared the postactivation potentiation (PAP) response of the hex bar deadlift (HBD) and back squat (BS) exercises. The PAP response between different levels of athletes was also compared. Ten professional and 10 amateur rugby league players performed 2 experimental sessions. Participants performed a countermovement jump (CMJ) before and 2, 4, 6, 8, 10, 12, 14, and 16 minutes after a conditioning activity (CA) that contained 1 set of 3 repetitions at 93% 1 repetition maximum of either HBD or BS. A force platform determined peak power output (PPO), force at PPO, velocity at PPO, and jump height of each CMJ. Surface electromyography (EMG) of the vastus lasteralis, rectus femoris, tibialis anterior, and gastrocnemius medialis of each participant's dominant leg was recorded during each CMJ. A further 10 participants performed a control trial without a CA. The HBD expressed PAP between 2 and 6 minutes post-CA, whereas the BS did not. The HBD exhibited a significantly (p ≤ 0.05) greater PAP response than the BS for PPO. There were no significant (p > 0.05) differences between stronger and weaker players. There were no significant (p > 0.05) changes in the EMG variables. These results suggest that HBD is a suitable CA for eliciting PAP in stronger and weaker athletes. Strength and conditioning coaches should consider the CA and time frame between the CA and the plyometric exercise for optimal PAP responses.

Age-related reductions in strength and power are considered to negatively impact balance control, but the existence of a direct association is still an issue of debate. This is possibly due to the fact that balance assessment is complex, reflects different underlying physiologic mechanisms and involves quantitative measurements of postural sway or timing of performance during balance tasks. The present study evaluated the moderator effect of static postural control on the association of power and strength with dynamic balance tasks. Fifty-seven healthy 65–75 year old individuals performed tests of dynamic functional balance (walking speed under different conditions) and of strength, power and static postural control. Dynamic balance performance (walking speed) was associated with lower limb strength and power, as well as postural control under conditions requiring postural adjustments (narrow surface walking r 2 = 0.31, p

The Nordic Hamstring Exercise (NHE) has been introduced as a training tool to improve the efficiency of eccentric hamstring muscle contraction. The aim of this study was to perform a biomechanical analysis of the NHE. Eighteen participants (20.4±1.9years) performed two sets of five repetitions each of the NHE and maximal eccentric voluntary contraction (MEVC) of the knee flexors on an isokinetic dynamometer whilst knee angular displacement and electrical activity (EMG) of biceps femoris were measured. EMG was on average higher during the NHE (134.3% of the MEVC). During the forward fall of the NHE, the angle at which a sharp increase in downward velocity occurred varied between 47.9 and 80.5deg, while the peak knee angular velocity (pVelocity) varied between 47.7 and 132.8degs(-1). A significant negative correlation was found between pVelocity and peak EMG (r=-0.62, p

Tensiomyography (TMG) is a technique utilised to measure mechanical and contractile properties of skeletal muscle. Aim of this study was to assess long-term stability of TMG across a variety of muscle conditions. Gastrocnemius Medialis of 21 healthy males was measured using TMG in rested conditions, after a warm-up, after a maximal voluntary contraction and after a fatigue protocol. Participants were re-tested on a second occasion 4 weeks apart. Among the parameters examined, Contraction Time, Sustain Time and Delay time exhibited a good level of absolute reliability (CV = 3.8–9.4%) and poor to excellent level of relative reliability (ICC = 0.56–0.92). On the other hand, relative reliability was good to excellent for muscle Displacement (ICC = 0.86–0.96), whereas its level of absolute reliability was questionable (CV = 8.0–14.8%). Minimum detectable change was less than 20% in most conditions for the aforementioned parameters. Half-relaxation Time yielded overall insufficient reliability. In general, the level of reliability tended to increase after the maximal voluntary contraction and the fatigue protocol were administered, probably because of more controlled conditions preceding the measurement. Information about the long-term stability of TMG across different muscle conditions is essential when intervention studies are undertaken with an exercising population, particularly athletes.

PURPOSE This study investigated the effect of knee joint angle and contraction intensity on the coactivation of the hamstring muscles (when acting as antagonists to the quadriceps) in young and older individuals of both sexes. METHODS A total of 25 young (24 ± 2.6 yr) and 26 older (70 ± 2.5 yr) healthy men and women participated. Maximal voluntary isometric contraction of the knee extensors and flexors was assessed at two knee joint angles (90° and 60°, 0° = full extension). At each angle, participants performed submaximal contractions of the knee extensors (20%, 50%, and 80% maximal voluntary isometric contraction), whereas surface EMG was simultaneously acquired from the vastus lateralis and biceps femoris muscles to assess the level (EMG root-mean-square) of agonist activation and antagonist coactivation. Subcutaneous adipose tissue in the areas corresponding to surface EMG electrode placements was measured via ultrasonography. RESULTS The contractions performed at 90° knee flexion demonstrated higher levels of antagonist coactivation (all P < 0.01) and agonist activation (all P < 0.01) as a function of contraction intensity compared with the 60° knee flexion. Furthermore, after controlling for subcutaneous adipose tissue, older participants exhibited a higher level of antagonist coactivation at 60° knee flexion compared with young participants (P < 0.05). CONCLUSIONS The results of the present study suggest that 1) the antagonist coactivation is dependent on knee joint angle and contraction intensity and 2) subcutaneous adipose tissue may affect the measured coactivation level likely because of a cross-talk effect. Antagonist coactivation may play a protective role in stabilizing the knee joint and maintaining constant motor output.

This study used surface electromyography (EMG) to investigate the regions and patterns of activity of the external oblique (EO), erector spinae longissimus (ES), multifidus (MU) and rectus abdominis (RA) muscles during walking (W) and pole walking (PW) performed at different speeds and grades. Eighteen healthy adults undertook W and PW on a motorized treadmill at 60% and 100% of their walk-to-run preferred transition speed at 0% and 7% treadmill grade. The Teager-Kaiser energy operator was employed to improve the muscle activity detection and statistical non-parametric mapping based on paired t-tests was used to highlight statistical differences in the EMG patterns corresponding to different trials. The activation amplitude of all trunk muscles increased at high speed, while no differences were recorded at 7% treadmill grade. ES and MU appeared to support the upper body at the heel-strike during both W and PW, with the latter resulting in elevated recruitment of EO and RA as required to control for the longer stride and the push of the pole. Accordingly, the greater activity of the abdominal muscles and the comparable intervention of the spine extensors supports the use of poles by walkers seeking higher engagement of the lower trunk region.

The purpose of this study was to investigate the influence of sex and fatigue on knee extensor peak torque (PT), muscle stiffness (MS) of the vastus lateralis (VL) and knee joint musculoarticular stiffness (MAS) in young adults. Twenty-two male and 22 female recreational athletes participated. Males were characterised by higher relaxed [pre-: males 364.43 (52.00) N · m–1, females 270.27 (37.25) N · m–1; post-: males 446.75 (83.27) N · m–1, females 307.39 (38.58) N · m–1] and contracted [pre-: males 495.07 (71.04) N · m–1, females 332.34 (85.42) N · m–1; post-: males 546.37 (90.74) N · m–1, females 349.21 (85.55) N · m–1] MS of the VL, and knee joint MAS [pre-: males 1450.11 (507.98) N · m–1, females 1027.99 (227.33) N · m–1; post-: males 1345.81 (404.90) N · m–1, females 952.78 (192.38) N · m–1] than females pre- and post-fatigue. A similar finding was observed in pre-fatigue normalised knee extensor PT [pre-: males 2.77 (0.42) N · m kg–1, females 2.41 (0.40) N · m kg–1, post-: males 2.53 (0.54) N...

This study aimed to investigate the influence of locally and generally induced fatigue on the stiffness properties of the knee joint.Twenty-two male (24.9 ± 4.5 yr, 1.78 ± 0.06 m, 75.4 ± 6.4 kg, 23.9 ± 1.8 kg·m) and 18 female (21.1 ± 1.5 yr, 1.66 ± 0.05 m, 63.4 ± 6.5 kg, 22.9 ± 2.5 kg·m) amateur athletes participated. Peak torque (PT) of the knee extensor musculature, muscle stiffness (MS) of the vastus lateralis, and musculoarticular stiffness (MAS) of the knee joint were assessed pre- and postlocally and generally induced fatigue (undertaken on two separate days with a 1-wk interval).Males were characterized by higher values of MAS, relaxed and contracted MS, normalized PT (PT/body mass), and normalized MAS (MAS/external load) irrespective of time point (P0.05).Contracted MS increased more (P0.01) and normalized PT decreased more (P = 0.03) in males than in females postfatigue. Significant increases occurred in MAS in females (P = 0.01); relaxed MS (males, P0.001; females, P0.001), contracted MS (males, P0.001; females, P = 0.04), and normalized MAS (males, P = 0.001; females, P = 0.01) in both sexes; and normalized contracted MS (contracted MS/external load) in males (P0.001). Normalized PT decreased significantly in males (P0.01) postfatigue.Contracted MS (P = 0.01) and MAS (P = 0.05) decreased significantly in males post-fatigue.The stiffness properties of the knee joint are influenced by locally and generally induced fatigue, with different responses being observed in males and females.

The aim of this study was to examine the concurrent validity of 2 portable systems for vertical jump (VJ) assessment under field conditions. The VJ flight times assessed using an optical mat (Optojump) and an accelerometer-based (Myotest) system were compared with that of a force platform. The flight times recorded during a countermovement jump (CMJ) were collected from 20 rugby players (n = 86 jumps) concurrently using the 3 tracking systems. Significant bias between the Force platform and either the Optojump (bias = 0.006 ± 0.007; 95% confidence interval [CI] 0.004-0.007 seconds) and Myotest (bias = -0.031 ± 0.021; 95% CI 0.035 to -0.026s; p < 0.0001) occurred. A nearly perfect correlation was found between force platform and Optojump (r = 0.99; 95% CI 0.098-0.99; p < 0.0001). Force platform and Myotest (r = 0.89; 95% CI 0.084-0.93; p < 0.0001) flight times showed very large association. Difference between Optojump and Myotest systems was significant (-0.036 ± 0.021 seconds; 95% CI -0.041 to -0.032; p < 0.0001), which results in Myotest mean flight time being approximately 7.2% longer than the Optojump flight time. The association between Optojump and Myotest was nearly perfect (r = 0.91, 95% CI 0.86-0.94; p < 0.0001). This study showed that the Optojump and Myotest systems possess convergent validity and can be successfully used under field conditions to assess VJ while performing a CMJ. However, caution should be exercised when interpreting data obtained from different portable systems for field measurement.

Purpose To examine tibial acceleration and muscle activation during overground (OG), motorised treadmill (MT) and non-motorised treadmill conditions (NMT) when walking, jogging and running at matched velocities. Methods An accelerometer recorded acceleration at the mid-tibia and surface EMG electrodes recorded rectus femoris (RF), semitendinosus (ST), tibialis anterior (TA) and soleus (SL) muscle activation during OG, MT and NMT locomotion whilst walking, jogging and running. Results The NMT produced large reductions in tibial acceleration when compared with OG and MT conditions across walking, jogging and running conditions. RF EMG was small-moderately higher in the NMT condition when compared with the OG and MT conditions across walking, jogging and running conditions. ST EMG showed large and very large increases in the NMT when compared to OG and MT conditions during walking whilst SL EMG found large increases on the NMT when compared to OG and MT conditions during running. The NMT condition generated very large increases in step frequency when compared to OG and MT conditions during walking, with large and very large decreases during jogging and very large decreases during running. Conclusions The NMT generates large reductions in tibial acceleration, moderate to very large increases in muscular activation and large to very large decreases in cycle time when compared to OG and MT locomotion. Whilst this may decrease the osteogenic potential of NMT locomotion, there may be uses for NMTs during rehabilitation for lower limb injuries.

Context:Assessments of skeletal-muscle functional capacity often necessitate maximal contractile effort, which exacerbates muscle fatigue or injury. Tensiomyography (TMG) has been investigated as a means to assess muscle contractile function after fatigue; however, observations have not been contextualized by concurrent physiological measures.Objective:To measure peripheral-fatigue-induced alterations in mechanical and contractile properties of the plantar-flexor muscles through noninvasive TMG concurrently with maximal voluntary contraction (MVC) and passive muscle tension (PMT) to validate TMG as a gauge of peripheral fatigue.Design:Pre- and posttest intervention with control.Setting:University laboratory.Participants:21 healthy male volunteers.Interventions:Subjects’ plantar flexors were tested for TMG parameters, along with MVC and PMT, before and after either a 5-min rest period (control) or a 5-min electrical-stimulation intervention (fatigue).Main Outcome Measures:Temporal (contraction velocity) and spatial (radial displacement) contractile parameters of the gastrocnemius medialis were recorded through TMG. MVC was measured as an indicator of muscle fatigue, and PMT was measured to assess muscle stiffness.Results:Radial displacement demonstrated a fatigue-associated reduction (3.3 ± 1.2 vs 4.0 ± 1.4 mm, P = .031), while contraction velocity remained unaltered. In addition, MVC significantly declined by 122.6 ± 104 N (P < .001) after stimulation (fatigue). PMT was significantly increased after fatigue (139.8 ± 54.3 vs 111.3 ± 44.6 N, P = .007).Conclusions:TMG successfully detected fatigue, evident from reduced MVC, by displaying impaired muscle displacement accompanied by elevated PMT. TMG could be useful in establishing skeletalmuscle fatigue status without exacerbating the functional decrement of the muscle.

This study investigated the kinematic variability and the local stability of walking and pole walking using two tri-axial accelerometers placed on the seventh cervical (C7) and the second sacral (S2) vertebrae of twenty-one adults. Each participant performed three 1-min trials of walking and pole walking on a motorized treadmill (60, 80, 100% of the preferred walk-to-run transition speed). Forty strides per trial were used to calculate, in all directions of C7 and S2, the median of the stride-to-stride median absolute deviation (medMAD) and the local divergence exponent (λ). Generalised estimating equations and pairwise contrasts revealed, during pole walking, a higher medMAD (all directions, most speeds, C7 level only), and a lower λ (all directions, all speeds, both C7 and S2 level). As speed increased, so did medMAD (all directions, both walking with or without poles), with higher values at C7 compared to S2 level. A similar effect was observed for λ in the vertical direction (walking and pole walking), and in the anterior-posterior direction (only pole walking). An increase in speed brought about a λ reduction in the medial-lateral direction (C7 level only), especially during walking. Finally, both medMAD and λ were higher at C7 than S2 level (all directions, both walking and pole walking) except for λ in the anterior-posterior direction, which resulted higher in walking (C7 level only). In conclusion, despite a higher kinematic variability, pole walking appears to be more locally stable than walking at any speed, especially at C7 level.

Stiffness, the relationship between applied load and elastic deformation, is an important neuromechanical component related to muscular performance and injury risk. The free-oscillation technique is a popular method for stiffness assessment. There has been wide application of this technique assessing a variety of musculature, including the triceps surae, knee flexors, knee extensors and pectorals. The methodology involves the modelling of the system as a linear damped mass-spring system. The use of such a model has certain advantages and limitations that will be discussed within this review. Perhaps the major advantage of such a model is the specificity of the measure, whereby it is possible for the assessment conditions to simulate the type of loading witnessed during functional tasks and sporting situations. High levels of reliability and construct validity have typically been reported using such procedures. Despite these assurances of accuracy, a number of issues have also been identified. The literature reveals some concerns surrounding the use of a linear model for stiffness assessment. Further, procedural issues surrounding the administration of the perturbation, attention focus of the participant during the perturbation, signal collection, data processing and analysis, presentation of stiffness as a linear or torsional value, assessment load (single vs multiple vs maximal) and the stiffness-load relationship have been identified, and are all fundamentally related to the quality of the calculated output data. Finally, several important considerations for practitioners have been recommended to ensure the quality and consistency of stiffness data collection, processing and interpretation. © 2011 Adis Data Information BV. All rights reserved.

The aim of this study was to assess the criterion validity of a submaximal field test (Intermittent Shuttle-Running Test [ISRT]) for lactate threshold (LT) detection in young basketball players. Fourteen basketball players (age 15.3 +/- 0.6 years, height 182 +/- 4.6 cm, and body mass 71.6 +/- 6.3 kg) were submitted in random order and on separate occasions, to ISRT (20-m shuttle running for 4 minutes at 9, 10 and 11 kmxh-1) and to a treadmill intermittent progressive test (criterion validity, TM) devised for the assessment of LT (4-minute stages at 8, 10, 12, 14 kmxh-1). Blood-lactate concentrations [La]b were assessed taking earlobe blood samples at rest and immediately after each of the 4-minute running steps considered for ISRT and TM. Lactate threshold was considered as the running speed attained at 1 mmolxL-1 [La]b above resting levels. Results showed that speed at LT during ISRT and TM was significantly related (r = 0.82, p0.001). However, speed at LT during the ISRT showed to be significantly lower than the speed at LT during TM (10.1 +/- 1.7 vs. 12 +/- 2.3 kmxh-1, p0.001). During ISRT, players attained 80 +/- 4.7, 87 +/- 4.4, and 92 +/- 3.0% of maximal heart rate (HR) at 9, 10, and 11 kmxh-1, respectively. This study results show that ISRT may be used as a valid field test to assess submaximal aerobic fitness in young team-sport players. Continuous 20-m shuttle running performed at 11 km.h revealed to elicit HR in the range of those reported to induce aerobic-fitness development in trained subjects. In light of study finding, ISRT may be considered in testing batteries for basketball players to complement anaerobic fitness and agility.

The aims of this study were to assess the criterion validity and the accuracy in estimating maximal aerobic power (VO2max) of a popular shuttle running field test (multistage fitness test [MSFT]) in women soccer players. Twenty-six women soccer players (age 12.1+/-0.9 years, body mass 50+/-9.2 kg, and height 155+/-5.7 cm) were tested over separate occasions for VO2max (VO2max test) and MSFT performances with (MSFT peak oxygen uptake) or without (MSFT) gas analysis. Data showed that the VO2max estimation using the MSFT predicting nomogram was significantly lower than MSFT VO2peak (32.7+/-3.9 vs. 40.1+/-5.9 ml.kg(-1).min(-1); p0.001). No significant difference between VO2max test and MSFT for maximal VO2 and heart rate (HR) was observed (38.7+/-4.7 vs. 40.1+/-5.9 ml.kg(-1).min(-1) and 203+/-5.3 vs. 200+/-9.8 beats.min(-1); p0.05; n=15). The MSFT performance (950+/-213 m) results significantly correlated with MSFT-VO2peak (r=0.70; p0.001). This study results showed that the MSFT predicting nomogram significantly underestimated VO2peak. Average difference being in the order of 23% of the estimated value. Resulting MSFT-VO2peak significantly related to MSFT performance, and this test may be considered as an indirect measure of individual VO2max in young women soccer players. Furthermore, MSFT may be used as a valid test to assess VO2peak and HRmax when a portable gas analyzer and a HR monitor are available. However, great individual differences may occur. In light of this study results, it is suggested to consider MSFT performance (distance covered) and not estimated VO2max when dealing with young women soccer players.

This study investigated the effects of gender, age, and dominance on upper and lower limb muscle function. One hundred and fifty-two males and females aged 20-30 and 40-80 years were recruited. Maximal voluntary isometric strength (MVC) and rate of force development (RFD) of the knee extensor muscles, and handgrip MVC were measured bilaterally as indicators of lower and upper limb muscle function, respectively. In both sexes, significant main effects were found for age (knee extension MVC, RFD, and handgrip MVC) and limb dominance (handgrip MVC). Men exhibited a steeper age-related decline in muscle function than women, particularly in the lower limb [dominant limb: knee extension MVC -56% (men) vs. -35% (women); handgrip MVC -30% (men) vs. -26% (women); RFD -67% (men) vs. -47% (women); non-dominant limb: knee extension MVC -49% (men) vs. -36% (women); handgrip MVC -26% (men) vs. -24% (women); RFD -62% (men) vs. -44% (women)]. Although men showed a higher rate of decline in muscle function, in absolute terms they demonstrated better muscle function than women in all age groups, which has important implications for independence and quality of life. A clear asymmetry in muscle function was evident in both sexes only for handgrip MVC.

The lateral-medial displacement (LF) and the overall drift from a straight path (DT) were quantified and compared in 5 top-level (TLS) and 5 low-level (LLS) crawl swimmers. Sixteen repetitions of 25-m crawl at increasing intensity were performed and videotaped. The performances were divided into 3 intensities (< 80 %, 80 - 90 % and > 90 % of maximal speed). LF was expressed as overlength swum (OLS) and coefficient of variation (CV) of the Z-component movement. OLS revealed a significant main effect for swimmer level (p < 0.01), intensity (p < 0.01) and their interaction (0.48, 0.37, 0.31-m for TLS and 0.47, 0.43, 0.44-m for LLS, p < 0.05). CV was significantly higher in LLS at the lowest (0.69 vs. 0.22, p < 0.05) and highest intensity (0.71 vs. 0.33, p < 0.05). DT, expressed as the slope of the linear regression of position data vs. time, was significantly higher in LLS only at the highest intensity (0.025 vs. 0.013, p < 0.05). The amount of dissipated energy due to LF, quantified by means of discrete Fourier analysis, revealed a difference only when the 0 - 5 Hz and 5 - 10 Hz spectral windows were analysed separately. While LF has a practical significance since it contributes to increase drag, DT is negligible at least for short-distance events.

Non-motorised underwater treadmills are commonly used in fitness activities. However, no studies have examined physiological and biomechanical responses of walking on non-motorised treadmills at different intensities and depths. Fifteen middle-aged healthy women underwent two underwater walking tests at two different depths, immersed either up to the xiphoid process (deep water) or the iliac crest (shallow water), at 100, 110, 120, 130 step-per-minute (spm). Oxygen consumption (VO2), heart rate (HR), blood lactate concentration, perceived exertion and step length were determined. Compared to deep water, walking in shallow water exhibited, at all intensities, significantly higher VO2 (+13.5%, on average) and HR (+8.1%, on average) responses. Water depth did not influence lactate concentration, whereas perceived exertion was higher in shallow compared to deep water, solely at 120 (+40%) and 130 (+39.4%) spm. Average step length was reduced as the intensity increased (from 100 to 130 spm), irrespective of water depth. Expressed as a percentage of maximum, average VO2 and HR were: 64-76% of peak VO2 and 71-90% of maximum HR, respectively at both water depths. Accordingly, this form of exercise can be included in the "vigorous" range of exercise intensity, at any of the step frequencies used in this study.