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Context: Horizontal hops can provide insight into how athletes can tolerate high-intensity single-leg stretch loads and are commonly used in athlete monitoring and injury management. Variables like flight, contact, and total time provide valuable diagnostic information to sports science professionals. However, gold-standard assessment tools (eg, 3-dimensional motion capture, force plates) require monetary and technological resources. Therefore, we used a tablet and free software to determine the between-rater, within-rater, and test-retest variability of the temporal events of multiple horizontal hop tests., Design: Reliability study., Methods: Nine healthy males (20.8 [1.3] y, 71.4 [9.8] kg, 171.7 [4.5] cm) across various university sports teams and clubs volunteered and performed several triple (3-Hop) and quintuple (5-Hop) horizontal hops over 3 testing sessions. Six raters detected temporal events from video to determine between-rater variability, while a single rater quantified within-session and test-retest variability. The temporal variables of flight time, ground contact time for each individual hop, and the total time of each hoping series were determined. The consistency of measures was interpreted using the coefficient of variation and interclass correlation coefficients (ICC)., Results: Good to excellent between-rater consistency was observed for all hops (ICC = .85-1.00). Absolute (coefficient of variation ≤ 2.0%) and relative consistency (ICC = .98-1.00) was excellent. Test-retest variability showed acceptable levels of absolute consistency (coefficient of variation ≤ 8.7%) and good to excellent consistency in 10/16 variables (ICC = .81-.93), especially those later in the hopping cycle., Conclusions: A tablet and free digitizing software are reliable in detecting temporal events during multiple horizontal hops, which could have exciting implications for power diagnostics and return-to-play decisions. Therefore, rehabilitation and performance professionals can confidently utilize the highly accessible equipment from this study to track multiple hop performances.

Eccentric quasi-isometric (EQI) contractions (maintaining a yielding contraction for as long as possible, beyond task failure) have gained interest in research and applied settings. However, little is known regarding the biomechanical profile of EQIs. Fourteen well-trained males performed four maximal effort knee-extensor EQIs, separated by 180 seconds. Angular impulse, velocity, and time-under-tension through the 30-100º range of motion (ROM), and in eight ROM brackets were quantified. Statistical parametric mapping, analyses of variance, and standardised effects (Hedges' g (ES), %Δ) detected between-contraction joint-angle-specific differences in time-normalised and absolute variables. Mean velocity was 1.34º·s -1 with most (62.5 ± 4.9%) of the angular impulse imparted between 40-70º. Most between-contraction changes occurred between 30-50º ( p ≤ 0.067, ES = 0.53 ± 0.31, 60 ± 52%), while measures remained constant between 50-100º (= 0.069-0.83, ES = 0.10 ± 0.26, 14.3 ± 24.6%). EQIs are a time-efficient means to impart high cumulative mechanical tension, especially at short to medium muscle lengths. However, angular impulse distribution shifts towards medium to long muscle lengths with repeat contractions. Practitioners may utilise EQIs to emphasize the initial portion of the ROM, and limit ROM, or apply EQIs in a fatigued state to emphasize longer muscle lengths.

Background: The inclusion of skateboarding in the Olympics suggests that athletes and coaches are seeking ways to enhance their chances of succeeding on the world stage. Understanding what constitutes performance, and what physical, neuromuscular, and biomechanical capacities underlie it, is likely critical to success., Objective: The aim was to overview the current literature and identify knowledge gaps related to competitive skateboarding performance and associated physical, technical, and tactical demands of Olympic skateboarding disciplines., Methods: A systematic scoping review was performed considering the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (Extension for Scoping Reviews) guidelines. Data sources were MEDLINE (Ovid), Scopus, SPORTDiscus, and PubMed. We included all peer-reviewed literature after 1970 describing the physiological, neuromuscular, biomechanical, and/or tactical aspects of skateboarding., Results: Nineteen original articles explored the physiological (n = 9), biomechanical (n = 8), and technical (n = 10) demands of skateboarding. No research explored the tactical demands of competition. Moreover, although competitive males (n = 2 studies) and females (n = 1 study) were recruited as participants, no research directly related skateboarding demands to performance success in competitive environments., Conclusions: Ultimately, what constitutes and distinguishes competitive skateboarding is unexplored. There is some evidence indicating aspects of the sport require flexibility and elevated and fast force output of the lower limbs, which may be valuable when attempting to maximise ollie height. Nonetheless, a lack of ecological validity, such as using static ollie tests as opposed to rolling, restricted our ability to provide practical recommendations, and inconsistency of terminology complicated delineating discipline-specific outcomes. Future researchers should first look to objectively identify what skaters do in competition before assessing what qualities enable their performance., (© 2024. The Author(s).)

The importance of hip adductor strength for injury prevention and performance benefits is well documented. The purpose of this study was to establish the intra- and inter-day variability of peak force (PF) of a groin squeeze protocol using a custom-designed compression strain gauge device. Sixteen semi-professional soccer players completed three trials over three separate testing occasions with at least 24-h rest between each session. The main findings were that the compression strain gauge was a reliable device for measuring PF within and between days. All intraclass correlations were higher than 0.80 and coefficients of variations were below 10% across the different sessions and trials. Due to the information gained through the compression strain gauge, the higher sampling frequency utilized, portability, and the relatively affordable price, this device offers an effective alternative for measuring maximal strength for hip adduction., Competing Interests: John B. Cronin owns stock in Kiwi Texas LLC, a funder of this research. Dana Ye‐Lee is an employee for associated projects, funded by Kiwi Texas LLC. The remaining authors have no conflicts of interest to declare., (© 2024 The Authors. Healthcare Technology Letters published by John Wiley & Sons Ltd on behalf of The Institution of Engineering and Technology.)

Context: Intrasession reliabilities of isometric knee extension kinetics via portable strain gauge have been reported across several knee joint angles and constraints. However, intersession variabilities, which are more valuable, have yet to be determined. Therefore, we aimed to quantify the intersession variability of knee extension kinetics over 3 testing sessions using an affordable and portable strain gauge., Design: Participants performed maximum voluntary isometric contractions of the knee extensors over 3 sessions., Methods: Eleven (6 men and 5 women; 31 [6.4] y) volunteers performed maximum voluntary isometric contractions in constrained (isokinetic setup with thigh and chest straps) and unconstrained (treatment plinth) conditions. Peak force (PF), peak rate of force development, rate of force development (RFD), and impulse (IMP) from 20% to 80% of PF were assessed. Means, SDs, percentage changes, minimal detectable changes, coefficients of variation (CV), and intraclass correlation coefficients (ICC) were calculated and reported., Results: PF had the lowest intersession variability regardless of condition (CV = 5.5%-13.8%, ICC = .67-.93). However, variability of peak rate of force development (CV [range] = 12.2%-24.7%, ICC = .50-.78), RFD (CV = 10.0%-26.8%, ICC = .48-.84), and IMP (CV = 15.2%-35.4%, ICC = .44-.88) was moderate at best. The constrained condition (CV [SD] = 14.1% [4.8%], ICC = .74 [.08]) had lower variability compared with the plinth (CV = 19.8% [7.9%], ICC = .68 [.15]). Variability improved from sessions 1 to 2 (CV = 20.4% [7.7%], ICC = .64 [.14]) and to sessions 2 to 3 (CV = 15.3% [6.4%], ICC = .76 [.10])., Conclusions: PF can be assessed regardless of setup. However, RFD and IMP changes across sessions should be approached with caution. Backrests and thigh straps improve RFD and IMP variability, and at least 1 familiarization session should be provided before relying on knee-extensor kinetics while utilizing a portable strain gauge.

Context: Light lower-limb wearable resistance has little effect on running biomechanics. However, asymmetrical wearable resistance may potentially alter the kinetics and kinematics of high speed, enabling greater loading or unloading of an injured or rehabilitative lower limb., Design: A cross-sectional study design was used to quantify the influence of asymmetric calf loading on the kinematics and kinetics during 90% maximum sprinting velocity., Methods: Following a familiarization session, 12 (male = 7 and female = 5) physically active volunteers ran at 90% of maximal velocity. In random order, participants ran with zero (0) wearable resistance and with loads of 300 g (L300) and 600 g (L600) fixed to one shank. A nonmotorized treadmill quantified vertical and horizontal kinetics and step kinematics. The kinetics and kinematics of the loaded (L0, L300, and L600) and unloaded (UL; UL0, UL300, and UL600) limbs were compared., Results: Vertical step ground reaction force of the loaded limb tended to increase between unloaded and 300 and 600 conditions (effect size [ES] = 0.48 to 0.76, all P ≤ .12), while the horizontal step force of the UL tended to decrease (ES = 0.54 to 1.32, all P ≤ .09) with greater external loading. Step length increased in the UL in 0 versus 300 and 600 conditions (ES = 0.60 to 0.70, all P ≤ .06). Step frequency decreased in the ULs in unloaded versus 300 and 600 conditions (ES = 0.73 to 1.10, all P ≤ .03). Mean step velocity tended to be greater in the ULs than the 300 and 600 conditions (ES = 0.52 to 1.01, all P ≤ .10). Only 4 of 16 variables were significantly different between the 300 and 600 conditions., Conclusions: Asymmetrical shank resistance could be used during high-speed running to reduce or increase the kinetic loading of an injured/rehabilitative limb during return to play protocols. Asymmetrical wearable resistance could also be used to alter step kinematics in runners with known asymmetries. Finally, meaningful alterations in high-speed running biomechanics can be achieved with only 300 g of shank loading.

Purpose: Eccentric quasi-isometric (EQI) contractions have been proposed as a novel training method for safely exposing the musculotendinous system to a large mechanical load/impulse, with few repetitions. However, understanding of this contraction type is rudimentary. We aimed to compare the acute effects of a single session of isotonic EQIs with isokinetic eccentric (ECC) contractions., Methods: Fifteen well-trained men performed a session of impulse-equated EQI and ECC knee extensions, with each limb randomly allocated to one contraction type. Immediately PRE, POST, 24/48/72 h, and 7 days post-exercise, regional soreness, quadriceps swelling, architecture, and echo intensity were evaluated. Peak concentric and isometric torque, rate of torque development (RTD), and angle-specific impulse were evaluated at each time point., Results: There were substantial differences in the number of contractions (ECC: 100.8 ± 54; EQI: 3.85 ± 1.1) and peak torque (mean: ECC: 215 ± 54 Nm; EQI: 179 ± 28.5 Nm). Both conditions elicited similar responses in 21/53 evaluated variables. EQIs resulted in greater vastus intermedius swelling (7.1-8.8%, ES = 0.20-0.29), whereas ECC resulted in greater soreness at the distal and middle vastus lateralis and distal rectus femoris (16.5-30.4%, ES = 0.32-0.54) and larger echogenicity increases at the distal rectus femoris and lateral vastus intermedius (11.9-15.1%, ES = 0.26--0.54). Furthermore, ECC led to larger reductions in concentric (8.3-19.7%, ES = 0.45-0.62) and isometric (6.3-32.3%, ES = 0.18-0.70) torque and RTD at medium-long muscle lengths., Conclusion: A single session of EQIs resulted in less soreness and smaller reductions in peak torque and RTD versus impulse-equated ECC contractions, yet morphological shifts were largely similar. Long-term morphological, architectural, and neuromuscular adaptations to EQI training requires investigation.