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Spinal excitability in humans is inhibited by both passively holding a static position with the muscle lengthened (static stretching) and by a single non-active lengthening movement. However, whilst immediately after a passive lengthening movement the inhibition persists for several seconds, there seem to be an immediate recovery following static stretching. This result is counter intuitive and could be attributed to methodological procedures. Indeed, differently to what has been done until now, in order to study whether static stretching has a transient effect on the neuromuscular pathway, the procedure should be repeated many times and measurements collected at different time points after stretching. In the present study we repeated 60 times 30 s static stretching of ankle plantar flexors and measured tap reflex (T-reflex), Hoffman reflex (H-reflex), and motor evoked potentials (MEPs) from the Soleus muscle at several time points, starting from immediately after until 30 s following the procedure. T-reflex was strongly inhibited (range 31-91%, p = 0.005) and the inhibition persisted for 30 s showing a slow recovery (r = 0.541, p = 0.037). H-reflex was not affected by the procedure. Stretching increased the size of the MEPs (p < 0.0001), differences at times 0 and 2 s after stretching (p = 0.015 and p = 0.047, respectively). These results confirm that static stretching reduces muscle spindle sensitivity. Moreover it is suggested that post-activation depression of Ia afferents, which is commonly considered the cause of H-reflex depression during both dorsiflexion and static stretching, vanished immediately following stretching or is counteracted by an increased corticospinal excitability. [ABSTRACT FROM AUTHOR]

Two experiments (n = 10) were conducted to determine the effects of roller massager (RM) on ankle plantar flexor muscle recovery after exercise-induced muscle damage (EIMD). Experiment 1 examined both functional [i.e., ankle plantar flexion maximal isometric contraction and submaximal (30%) sustained force; ankle dorsiflexion maximal range of motion and resistance to stretch; and medial gastrocnemius pain pressure threshold] and morphological [cross-sectional area, thickness, fascicle length, and fascicle angle] variables, before and immediately, 1, 24, 48, and 72 h after an EIMD stimulus. Experiment 2 examined medial gastrocnemius deoxyhaemoglobin concentration kinetics before and 48 h after EIMD. Participants performed both experiments twice: with (RM) and without (no-roller massager; NRM) the application of a RM (6 × 45 s; 20-s rest between sets). RM intervention did not alter the functional impairment after EIMD, as well as the medial gastrocnemius morphology and oxygenation kinetics (P > 0.05). Although, an acute increase of ipsilateral (RM = + 19%, NRM = −5%,P = 0.032) and a strong tendency for contralateral (P = 0.095) medial gastrocnemius pain pressure threshold were observed. The present results suggest that a RM has no effect on plantar flexors performance, morphology, and oxygenation recovery after EIMD, except for muscle pain pressure threshold (i.e., a soreness). [ABSTRACT FROM AUTHOR]

Background: Medial knee collapse can signal an underlying movement issue that, if uncorrected, can lead to a variety of knee injuries. Placing a band around the distal thigh may act as a proprioceptive aid to minimize medial collapse of the knee during squats; however, little is known about EMG and biomechanics in trained and untrained individuals during the squat with an elastic band added. Hypothesis/Purpose: To investigate the effects of the TheraBand® Band Loop on kinematics and muscle activity of the lower extremity during a standard barbell back squat at different intensities in both trained and untrained individuals. Study Design: Cross-sectional, repeated measures. Methods: Sixteen healthy, male, university aged-participants were split into two groups of eight, consisting of a trained and untrained group. Participants performed both a 3-repetition maximum (3-RM) and a bodyweight load squat for repetitions to failure. Lower extremity kinematics and surface electromyography of four muscles were measured bilaterally over two sessions, an unaided squat and a band session (band loop placed around distal thighs). Medial knee collapse, measured as a knee width index, and maximum muscle activity were calculated. Results: During the 3-RM, squat weight was unaffected by band loop intervention (p=0.486) and the trained group lifted more weight than the untrained group (p<0.007). The trained group had a greater squat depth for both squat conditions, regardless of the band (p=0.0043). Knee width index was not affected by the band during the eccentric phase of bodyweight squats in the trained (band: 0.76 ± 0.08, no band: 0.73 ± 0.08) or untrained group (band: 0.77 ± 0.70, no band: 0.75 ± 0.13) (p=0.670). During the concentric phase, knee width index was significantly lower for 3-RM squats, regardless of group. Conclusion: Despite minimal changes in kinematics for the untrained group, increased muscle activity with the band loop may suggest that a training aid may, over time, lead to an increase in barbell squat strength by increasing activation of agonist muscles more than traditional, un-banded squats. Greater maximal muscle activity in most muscles during band loop sessions may provide enhanced knee stability via increased activation of stabilizing muscles. Level of Evidence: 3 [ABSTRACT FROM AUTHOR]

BACKGROUND: Limited dorsiflexion range of motion (ROM) has been linked to lower limb injuries. Improving limited ankle ROM may decrease injury rates. Static stretching (SS) is ubiquitously used to improve ROM but can lead to decreases in force and power if performed prior to the activity. Thus, alternatives to improve ROM without performance decrements are needed. OBJECTIVES/PURPOSE: To compare the effects of SS and self massage (SM) with a roller massage of the calf muscles on ankle ROM, maximal voluntary contraction (MVC) force F100 (force produced in the first 100 ms of the MVC), electromyography (EMG of soleus and tibialis anterior) characteristics of the plantar flexors, and a single limb balance test. METHODS: Fourteen recreationally trained subjects were tested on two separate occasions in a randomized cross-over design. After a warm up, subjects were assessed for passive dorsiflexion ROM, MVC, and a single-limb balance test with eyes closed. The same three measurements were repeated after 10 minutes (min) of rest and prior to the interventions. Following the pre-test, participants randomly performed either SS or SM for 3 sets of 30 seconds (s) with 10s of rest between each set. At one and 10 min post-interventions the participants repeated the three measurements, for a third and fourth cycle of testing. RESULTS: Roller massage increased and SS decreased maximal force output during the post-test measurements, with a significant difference occurring between the two interventions at 10 min post-test (p < 0.05, ES = 1.23, 8.2% difference). Both roller massage (p < 0.05, ES = 0.26, ~4%) and SS (p < 0.05, ES = 0.27, ~5.2%) increased ROM immediately and 10 min after the interventions. No significant effects were found for balance or EMG measures. CONCLUSIONS: Both interventions improved ankle ROM, but only the self-massage with a roller massager led to small improvements in MVC force relative to SS at 10 min post-intervention. These results highlight the effectiveness of a roller massager relative to SS. These results could affect the type of warm-up prior to activities that depend on high force and sufficient ankle ROM. LEVEL OF EVIDENCE: 2 [ABSTRACT FROM AUTHOR]

BACKGROUND: Inverted positions may arise with emergencies, work or recreational activities. Vigilance which can involve cognition, attention, and decision making is required for activities of daily living, in addition to the avoidance and escape from life threatening situations. OBJECTIVE: The purpose of this study was to evaluate the effects of an inverted posture on vigilance, heart rate and blood pressure. METHODS: Heart rate (HR) and blood pressure (BP), vigilance tasks (Tower of London (ToL), Selective Attention and Response Competition (SARC), Attention Networks Test (ANT)), anxiety and reaction time were assessed with 8 male subjects in an initial seated upright position, followed an inverted posture and returning to an upright position. RESULTS: TOL was 63.4% and 40.7% slower and SARC was 10.4% and 11.7% slower during the inverted condition compared to the pre- and post-inversion upright assessments (p< 0.01). There were no significant changes in ANT. Systolic BP (p< 0.0001), diastolic BP (p=0.03), and HR (p< 0.01) decreased during inversion, whereas anxiety scores increased 25% and 51% compared to pre- and post-inversion upright conditions. CONCLUSIONS: Under inverted conditions, vigilance task capabilities and reaction time were significantly hampered. These decrements could substantially impact responses to emergency situations. [ABSTRACT FROM AUTHOR]

Purpose/Background: Proper strengthening of the core and upper extremities is important for muscular health, performance, and rehabilitation. Exercise devices have been developed that attempt to disrupt the center of gravity in order to activate the trunk stabilizing muscles. The objective of this study was to analyze the trunk and shoulder girdle muscle activation with double and single oscillating exercise devices (DOD and SOD respectively) in various planes. Methods: Twelve male subjects performed three interventions using both devices under randomized conditions: single-handed vertical orientation of DOD and SOD to produce 1) medio-lateral oscillation in the frontal plane 2) dorso-ventral oscillation in the sagittal plane and 3) single-handed horizontal orientation for superior and inferior oscillation in the transverse plane. Electromyographic (EMG) activity during the interventions of the anterior deltoid, triceps brachii, biceps brachii, forearm flexors as well as lower abdominal and back stabilizer muscles was collected, and were normalized to maximal voluntary contractions. A two way repeated measures ANOVA (2x3) was conducted to assess the influence of the devices and movement planes on muscle activation. Results: The DOD provided 35.9%, 40.8%, and 52.3% greater anterior deltoid, transverse abdominus (TA)/internal oblique (IO) and lumbo-sacral erector spinae (LSES) activation than did the SOD respectively. Effect size calculations revealed that these differences were of moderate to large magnitude (0.86, 0.48, and 0.61 respectively). There were no significant differences in muscular activation achieved between devices for the triceps brachii, biceps brachii and forearm flexor muscles. Exercise in the transverse plane resulted in 30.5%, 29.5%, and 19.5% greater activation than the sagittal and 21.8%, 17.2%, and 26.3% greater activation than the frontal plane for the anterior deltoid, TA/IO and LSES respectively. Conclusions: A DOD demonstrated greater muscular activity for trunk and shoulder muscle activation but does not provide an advantage for limb activation. Overall, oscillating the devices in the transverse plane provided greater muscular activation of the anterior deltoid, TA/IO and LSES than use of the devices during frontal or sagittal plane movements. [ABSTRACT FROM AUTHOR]

Purpose/Background: Proper strengthening of the core and upper extremities is important for muscular health, performance, and rehabilitation. Exercise devices have been developed that attempt to disrupt the center of gravity in order to activate the trunk stabilizing muscles. The objective of this study was to analyze the trunk and shoulder girdle muscle activation with double and single oscillating exercise devices (DOD and SOD respectively) in various planes. Methods: Twelve male subjects performed three interventions using both devices under randomized conditions: single-handed vertical orientation of DOD and SOD to produce 1) medio-lateral oscillation in the frontal plane 2) dorso-ventral oscillation in the sagittal plane and 3) single-handed horizontal orientation for superior and inferior oscillation in the transverse plane. Electromyographic (EMG) activity during the interventions of the anterior deltoid, triceps brachii, biceps brachii, forearm flexors as well as lower abdominal and back stabilizer muscles was collected, and were normalized to maximal voluntary contractions. A two way repeated measures ANOVA (2x3) was conducted to assess the influence of the devices and movement planes on muscle activation. Results: The DOD provided 35.9%, 40.8%, and 52.3% greater anterior deltoid, transverse abdominus (TA)/internal oblique (IO) and lumbo-sacral erector spinae (LSES) activation than did the SOD respectively. Effect size calculations revealed that these differences were of moderate to large magnitude (0.86, 0.48, and 0.61 respectively). There were no significant differences in muscular activation achieved between devices for the triceps brachii, biceps brachii and forearm flexor muscles. Exercise in the transverse plane resulted in 30.5%, 29.5%, and 19.5% greater activation than the sagittal and 21.8%, 17.2%, and 26.3% greater activation than the frontal plane for the anterior deltoid, TA/IO and LSES respectively. Conclusions: A DOD demonstrated greater muscular activity for trunk and shoulder muscle activation but does not provide an advantage for limb activation. Overall, oscillating the devices in the transverse plane provided greater muscular activation of the anterior deltoid, TA/IO and LSES than use of the devices during frontal or sagittal plane movements. [ABSTRACT FROM AUTHOR]

Background: Foam rollers are used to mimic myofascial release techniques and have been used by therapists, athletes, and the general public alike to increase range of motion (ROM) and alleviate pressure points. The roller-massager was designed to serve a similar purpose but is a more portable device that uses the upper body rather than body mass to provide the rolling force. Objectives/Purpose: A roller massager was used in this study to examine the acute effects on lower extremity ROM and subsequent muscle length performance. Methods: Seven male and ten female volunteers took part in 4 trials of hamstrings roller-massager rolling (1 set - 5 seconds, 1 set - 10 seconds, 2 sets - 5 seconds, and 2 sets - 10 seconds) at a constant pressure (13 kgs) and a constant rate (120 bpm). A group of 9 participants (three male, six female) also performed a control testing session with no rolling intervention. A sit and reach test for ROM, along with a maximal voluntary contraction (MVC) force and muscle activation of the hamstrings were measured before and after each session of rolling. Results: A main effect for testing time (p<0.0001) illustrated that the use of the roller-massager resulted in a 4.3% increase in ROM. There was a trend (p=0.069) for 10s of rolling duration to increase ROM more than 5s rolling duration. There were no significant changes in MVC force or MVC EMG activity after the rolling intervention. Conclusions: The use of the roller-massager had no significant effect on muscle strength, and can provide statistically significant increases in ROM, particularly when used for a longer duration. [ABSTRACT FROM AUTHOR]

The purpose of the study was to determine the effects of static and dynamic stretching protocols within general and activity specific warm-ups. Nine male and ten female subjects were tested under four warm-up conditions including a 1) general aerobic warm-up with static stretching, 2) general aerobic warmup with dynamic stretching, 3) general and specific warm-up with static stretching and 4) general and specific warm-up with dynamic stretching. Following all conditions, subjects were tested for movement time (kicking movement of leg over 0.5 m distance), countermovement jump height, sit and reach flexibility and 6 repetitions of 20 metre sprints. Results indicated that when a sport specific warm-up was included, there was an 0.94% improvement (p = 0.0013) in 20 meter sprint time with both the dynamic and static stretch groups. No such difference in sprint performance between dynamic and static stretch groups existed in the absence of the sport specific warm-up. The static stretch condition increased sit and reach range of motion (ROM) by 2.8% more (p = 0.0083) than the dynamic condition. These results would support the use of static stretching within an activity specific warm-up to ensure maximal ROM along with an enhancement in sprint performance. [ABSTRACT FROM AUTHOR]

The objective of this study was to investigate the effect of expected and unexpected interpolated stimuli (IT) during a maximum voluntary contraction on quadriceps force output and activation. Two groups of male subjects who were either inexperienced (MI: no prior experience with IT tests) or experienced (ME: previously experienced 10 or more series of IT tests) received an expected or unexpected IT while performing quadriceps isometric maximal voluntary contractions (MVCs). Measurements included MVC force, quadriceps and hamstrings electromyographic (EMG) activity, and quadriceps inactivation as measured by the interpolated twitch technique (ITT). When performing MVCs with the expectation of an IT, the knowledge or lack of knowledge of an impending IT occurring during a contraction did not result in significant overall differences in force, ITT inactivation, quadriceps or hamstrings EMG activity. However, the expectation of an IT significantly (p < 0.0001) reduced MVC force (9.5%) and quadriceps EMG activity (14.9%) when compared to performing MVCs with prior knowledge that stimulation would not occur. While ME exhibited nonsignificant decreases when expecting an IT during a MVC, MI force and EMG activity significantly decreased 12.4% and 20.9% respectively. Overall, ME had significantly (p < 0.0001) higher force (14.5%) and less ITT inactivation (10.4%) than MI. The expectation of the noxious stimuli may account for the significant decrements in force and activation during the ITT. [ABSTRACT FROM AUTHOR]

The objective of this study was to determine the effects of muscle contraction intensity, neuromuscular fatigue, and noise on vigilance performance. Dependent variables included simple (reaction time and movement time) and complex (video game: Tetris) vigilance tasks (SVT and CVT respectively) and maximum voluntary contraction (MVC) force and activation. Vigilance tasks and MVC were randomly allocated to 5 minute blocks during a pre-test. Following the pre-test, the tests were again randomly allocated within three, 15 minute testing sessions over 65 minutes, while 1) being exposed to high (95 dB (A)) or low (53 dB (A)) levels of noise, and 2) performing muscle contractions at 20% and 5% of MVC, or no contractions. Ninety-five (95) dB (A) noise increased (p ≤ 0.01) SVT (reaction time and movement time combined) by 11.2% and decreased (p ≤ 0.01) CVT by 20%. Both 20% and 5% MVC impaired SVT and CVT to a similar extent, while no changes were seen with no contractions. Furthermore, neuromuscular fatigue had no apparent effect on vigilance task performance. These findings suggest that the distraction of noise and divided attention between muscle contraction and a vigilance task decreases performance. [ABSTRACT FROM AUTHOR]

Background: The present study compared corticospinal excitability to the biceps brachii muscle during arm cycling at a self-selected and a fixed cadence (SSC and FC, respectively). We hypothesized that corticospinal excitability would not be different between the two conditions. Methods: The SSC was initially performed and the cycling cadence was recorded every 5 s for one minute. The average cadence of the SSC cycling trial was then used as a target for the FC of cycling that the participants were instructed to maintain. The motor evoked potentials (MEPs) elicited via transcranial magnetic stimulation (TMS) of the motor cortex were recorded from the biceps brachii during each trial of SSC and FC arm cycling. Results: Corticospinal excitability, as assessed via normalized MEP amplitudes (MEPs were made relative to a maximal compound muscle action potential), was not different between groups. Conclusions: Focusing on maintaining a fixed cadence during arm cycling does not influence corticospinal excitability, as assessed via TMS-evoked MEPs. [ABSTRACT FROM AUTHOR]

This is the first study to examine corticospinal excitability (CSE) to antagonistic muscle groups during arm cycling. Transcranial magnetic stimulation (TMS) of the motor cortex and transmastoid electrical stimulation (TMES) of the corticospinal tract were used to assess changes in supraspinal and spinal excitability, respectively. TMS induced motor evoked potentials (MEPs) and TMES induced cervicomedullary evoked potentials (CMEPs) were recorded from the biceps and triceps brachii at two positions, mid-elbow flexion and extension, while cycling at 5% and 15% of peak power output. While phase-dependent modulation of MEP and CMEP amplitudes occurred in the biceps brachii, there was no difference between flexion and extension for MEP amplitudes in the triceps brachii and CMEP amplitudes were higher during flexion than extension. Furthermore, MEP amplitudes in both biceps and triceps brachii increased with increased workload. CMEP amplitudes increased with higher workloads in the triceps brachii, but not biceps brachii, though the pattern of change in CMEPs was similar to MEPs. Differences between changes in CSE between the biceps and triceps brachii suggest that these antagonistic muscles may be under different neural control during arm cycling. Putative mechanisms are discussed., Competing Interests: The authors declare no conflict of interest.

The purpose of this study was to describe the frequency-current (f-I) relationships of hindlimb alpha-motoneurones (MNs) in both anaesthetized and decerebrate rats in situ. Sprague-Dawley rats (250-350 g) were anaesthetized with ketamine and xylazine (KX) or subjected to a precollicular decerebration prior to recording electrophysiological properties from sciatic nerve MNs. Motoneurones from KX-anaesthetized rats had a significantly (P < 0.01) hyperpolarized resting membrane potential and voltage threshold (Vth), increased rheobase current, and a trend (P = 0.06) for a smaller after-hyperpolarization (AHP) amplitude compared to MNs from decerebrate rats. In response to 5 s ramp current injections, MNs could be categorized into four f-I relationship types: (1) linear; (2) adapting; (3) linear + sustained; and (4) late acceleration. Types 3 and 4 demonstrated self-sustained firing owing to activation of persistent inward current (PIC). We estimated the PIC amplitude by subtracting the current at spike derecruitment from the current at spike recruitment. Neither estimated PIC nor f-I slopes differed between fast and slow MNs (slow MNs exhibited AHP half-decay times > 20 ms) or between MNs from KX-anaesthetized and decerebrate rats. Motoneurones from KX-anaesthetized rats had significantly (P < 0.02) hyperpolarized ramp Vth values and smaller and shorter AHP amplitudes and decay times compared to MNs from decerebrate rats. Pentobarbitone decreased the estimated PIC amplitude and almost converted the f-I relationship from type 3 to type 1. In summary, MNs of animals subjected to KX anaesthesia required more current for spike initiation and rhythmic discharge but retained large PICs and self-sustained firing. The KX-anaesthestized preparation enables direct recording of PICs in MNs from intact animals.