Eccentric Peak Research Articles

Comparison of Three Eccentric Overload Training Strategies on Power Output and Interlimb Asymmetry in Youth Soccer Players.

Background: The present study compared the effects of performing the lateral squat exercise in three different formats from eccentric overload training on concentric/eccentric peak/mean power and inter-limb asymmetries in young soccer players. Methods: Forty-five young male (U-17) soccer players were distributed into three groups. Two groups performed the same training volume with both legs, beginning with the weaker leg (SVW, n = 15) or with the stronger leg (SVS, n = 15). The third group executed double volume with the weaker leg and also commenced with such leg (DVW, n = 15) in the lateral squat during a 10-week period. Pre- and post-intervention metrics included concentric and eccentric peak/mean power during the lateral squat test and their corresponding asymmetries. Results: All groups improved all power variables. Concentric mean and peak power asymmetry were substantially reduced in the SVW (ES: 0.89), DVW (ES: 0.43), and in SVW (ES: 1.60). Eccentric mean and peak power asymmetry were also substantially decreased in SVW (ES: 0.81) and in DVW (ES: 0.68). Between-group analyses showed substantially better performance in concentric and eccentric variables with stronger and weaker legs in SVW and DVW groups compared with SVS. Conclusions: Those groups which started with the weaker leg showed greater both power enhancements and reductions on inter-limb asymmetries.

Differences in Muscle Activity and Kinetics Between the Goblet Squat and Landmine Squat in Men and Women.

Collins, KS, Klawitter, LA, Waldera, RW, Mahoney, SJ, and Christensen, BK. Differences in muscle activity and kinetics between the goblet squat and landmine squat in men and women. J Strength Cond Res 35(10): 2661-2668, 2021-Squat exercise variations are widely used and extensively researched. However, little information exists on the goblet squat (GBS) and landmine squat (LMS) and differences between men and women. This study investigated the differences in muscle activity and kinetics between the GBS and the LMS in 16 men and 16 women. Five repetitions of each squat type were performed loaded at 30% of their body mass. Vertical and anteroposterior ground reaction forces for the eccentric and concentric phases and peak vertical force were recorded with a force plate. Electromyographic (EMG) signals were recorded for the vastus medialis (VM), vastus lateralis (VL), semitendinosus (ST), and biceps femoris (BF). Normalized mean EMG values and ground reaction forces were analyzed with repeated measures analysis of variance (p < 0.05). Significant main effects for squat condition and sex were found. The LMS reduced activity in the quadriceps (VM and VL) muscles and vertical forces, while increasing posterior horizontal forces. In the LMS, men showed decreased ST activity, whereas women had decreased BF activity. Women exhibited greater quadriceps activity in both the GBS and LMS and greater ST in the LMS. Women also produced greater eccentric vertical force in both the GBS and LMS and less posterior horizontal forces in the LMS. The LMS may be useful to balance hamstring to quadriceps activity, increase horizontal loading, and reduce vertical loading. Conversely, the GBS can better target quadriceps activity and increase vertical loading. Sex differences should be considered for training programs that include the GBS and LMS.

The Influence of Injury History on Countermovement Jump Performance and Movement Strategy in Professional Soccer Players: Implications for Profiling and Rehabilitation Foci.

Professional soccer players who have sustained a lower limb injury are up to 3× more likely to suffer a reinjury, often of increased severity. Previous injury has been shown to induce compensatory strategies during neuromuscular screening tests, which might mask deficits and lead to misinterpretation of readiness to play based on task outcome measures. To investigate the influence of previous injury in professional soccer players on countermovement jump (CMJ) performance and movement strategy. Cross-sectional. Professional soccer club competing in the English Championship (tier 2). Patients (or Other Participants): Outfield players with a minimum of 6 years as a professional. Players were categorized as previously injured (n = 10) or not injured (n = 10). All players completed double- and single-leg CMJ trials. CMJ performance was quantified as jump height and flight time:contraction time ratio. CMJ movement strategy was quantified as force-time history, differentiating eccentric and concentric phases and CMJ depth. Double-leg CMJ was not sensitive to previous injury in performance or movement strategy. In contrast, single-leg CMJ performance was impaired in players with previous injury, who generated significantly lower eccentric and concentric peak force and rate of force development, and a deeper countermovement. Impaired single-leg CMJ performance was also evident in the nonaffected limb of previously injured players, suggesting cross-contamination. Hierarchical ordering revealed that the eccentric phase of the CMJ contributed little to performance in previously injured players. In noninjured players, the eccentric rate of force development and concentric peak force were able to account for up to 89% of the variation in CMJ performance. Single-leg CMJ is advocated for player profiling, being more sensitive to previous injury, and negating the opportunity for interlimb compensation strategies. Movement strategy deficits in previously injured players suggest rehabilitation foci specific to eccentric force development.

Swing Phase Mechanics of Maximal Velocity Sprints-Does Isokinetic Lower-Limb Muscle Strength Matter?

Concentric hip and eccentric knee joint mechanics affect sprint performance. Although the biarticular hamstrings combine these capacities, empirical links between swing phase mechanics and corresponding isokinetic outcome parameters are deficient. This explorative study aimed (1)to explain the variance of sprint velocity, (2)to compare maximal sprints with isokinetic tests, (3)to associate swing phase mechanics with isokinetic parameters, and (4)to quantify the relation between knee and hip joint swing phase mechanics. A total of 22 sprinters (age = 22y, height = 1.81m, weight = 77kg) performed sprints and eccentric knee flexor and concentric knee extensor tests. All exercises were captured by 10 (sprints) and 4 (isokinetics) cameras. Lower-limb muscle balance was assessed by the dynamic control ratio at the equilibrium point. The sprint velocity (9.79 [0.49]m/s) was best predicted by the maximal knee extension velocity, hip mean power (both swing phase parameters), and isokinetic peak moment of concentric quadriceps exercise (R2 = 60%). The moment of the dynamic control ratio at the equilibrium point (R2 = 39%) was the isokinetic parameter with the highest predictive power itself. Knee and hip joint mechanics affected each other during sprinting. They were significantly associated with isokinetic parameters of eccentric hamstring tests, as well as moments and angles of the dynamic control ratio at the equilibrium point, but restrictedly with concentric quadriceps exercise. The maximal sprints imposed considerably higher loads than isokinetic tests (eg,13-fold eccentric knee joint peak power). Fast sprinters demonstrated distinctive knee and hip mechanics in the late swing phase, as well as strong eccentric hamstrings, with a clear association to the musculoarticular requirements of the swing phase in sprinting. The transferability of isokinetic knee strength data to sprinting is limited inter alia due to different hip joint configurations. However, isokinetic tests quantify specific sprint-related muscular prerequisites and constitute a useful diagnostic tool due to their predicting value to sprint performance.

Effects of Cross-Education After 6 Weeks of Eccentric Single-Leg Decline Squats Performed With Different Execution Times: A Randomized Controlled Trial.

Cross-education of strength refers to the strength gain that is transferred to the contralateral limb after a unilateral training program. Unilateral eccentric training using different muscle contraction times would improve the structural and functional properties of the untrained contralateral limb. Randomized controlled trial. Level 2. Thirty-six participants were randomized into a control group, experimental group 1 (EG6s; eccentric contraction runtime = 6 seconds) and experimental group 2 (EG3s; eccentric contraction runtime = 3 seconds). The thickness and elastographic index of the patellar tendon (PT), lean mass and fat percentage of the thigh, contractile properties of the vastus lateralis (VL), as well as isometric, concentric, and eccentric knee extensor peak torques, and eccentric single-leg decline squat (SLDSe) 1 repetition maximum (1-RM) were measured after 6 weeks of SLDSe training (3 times per week, 80% of 1-RM) and after 6 weeks of detraining in the untrained contralateral limb. After training, there was an increase in lean thigh mass of the untrained limb in both groups: EG6s (0.17 ± 0.29 kg;P = 0.03; effect size [ES] = 0.15) and EG3s (0.15 ± 0.23 kg; P = 0.04; ES = 0.19). Likewise, both EG6s (62.30 ± 19.09 kg; P < 0.001; ES = 4.23) and EG3s (68.09 ± 27.49 kg; P < 0.001; ES = 3.40) increased their 1-RM, isometric (EG6s: 48.64 ± 44.82 N·m, P < 0.001, ES = 0.63; EG3s: 34.81 ± 47.30 N·m, P = 0.004, ES = 0.38), concentric at 60 deg/s and 180 deg/s and eccentric at 60 deg/s and 180 deg/s knee extensor peak torques (P < 0.05) in the untrained limb. However, no differences were found in the contractile properties of the VL or in the thickness of the PT after eccentric training in either of the 2 experimental groups. Regardless of the runtime of the contraction, 6 weeks of SLSDe was effective for inducing structural and strength adaptations in the contralateral untrained limb. However, most of these adaptations were lost after 6 weeks of detraining. Our study suggests that cross-education training can be of great importance for clinical application and musculoskeletal and neuromuscular rehabilitative processes after unilateral injury.

Shoulder Isokinetic Strength Balance Ratio in Overhead Athletes: A Cross-Sectional Study.

BackgroundStudies have grouped different overhead sports and evaluated together the isokinetic strength of shoulder internal (IR) and external (ER) rotator muscles. However, muscular adaptations could be a consequence of the specific sport, and some strength imbalance between these muscles may exist as a consequence of the muscular demand unique to the sport. Therefore, grouping different overhead sports together may not be adequate.PurposeTo compare strength balance ratios between different overhead sports (volleyball, handball, swimming, judo, baseball, softball, functional movements performed at high-intensity interval training, and tennis) with a control athletic group (no overhead group).Study designCross-sectional study.MethodsA total of 237 athletes were submitted to isokinetic shoulder strength tests. The isokinetic concentric and eccentric peak torque values of shoulder internal IR and external ER rotator muscles were measured. Conventional (CR) and functional strength ratios (FR) were calculated.ResultsThere were no significant differences between the sports for the CR in the male group. Female softball athletes (90.4±13.6%) had a significantly higher CR than judo (67.3±6.9%), volleyball (74.9±15.9%), and swimming athletes (70.3±8.7%). In the female group, judo athletes had lower FR values (0.76±0.19) than soccer athletes (1.31±0.35), volleyball athletes (1.24±0.27), functional movements performed at high intensity (1.10±0.1), and softball athletes (1.40±0.39). Female handball athletes also had a lower FR (0.99±0.25) than soccer athletes (1.31±0.35) and softball athletes (1.40±0.39). Male handball (0.90±0.23), tennis (0.86±0.30), and judo (0.68±0.22) athletes had lower FR values than soccer athletes (1.20±0.21) and volleyball athletes (1.25±0.28).ConclusionsCR for males may be analyzed together, as there were no significant differences between them. However, for females, the CR for softball athletes should be analyzed individually. As there were several differences between the overhead sports according to the FRs, the authors suggest caution in grouping overhead athletes across multiple sports. These results could have important implications for the design of injury prevention and rehabilitation programs associated with the shoulder joint in overhead sports.Level of Evidence3

Relationship between lower limb power and dynamic stability in volleball players

Abstract Introduction As in all team sports, lower limb power is an important quality of any player. Especially when it comes to volleyball, a game that relies on jumping performance on almost every action except reception. Another crucially important quality of the lower limbs is dynamic stability. Without the latter, the frequency of injuries rises, and that is something any coach or player wants to avoid. The question arises: Are the two qualities related? Aim The study aimed to investigate the correlation between lower limb power and force measured using an inertial flywheel training/measuring device and dynamic stability evaluated through the Y balance test. Material and method The Y balance test was used for evaluating the lower limb dynamic stability of 8 Romanian volleyball players. In addition, using an inertial flywheel training system (kBox 4 Pro, Exxentric, Sweden) and kMeter II measuring device the following parameters where measured: average force AvF (N), average power AvP (W), concentric peak power ConPP (W), eccentric peak power EccPP(W). The relative peak power RPP (W/kg) was calculated by dividing concentric peak power by the weight of the volleyball player. The subjects performed 8 maximal squats using the kBox harness and the L (0,05 kgm2) flywheel Results Composite reach distance (CRD) means for the lower limbs have been compared using the t-test and although there is a difference of 1.8%, it isn’t significant, (p&lt;0,001). We have found a direct correlation between the average composite reach distance and relative peak power (r=0.71, p=0.045) and also with the average power (r=0.75, p=0.032) of the lower limbs. The composite reach distance for the right leg correlates with the relative peak power (r=0.73, p=0.036); average force (r=0.73, p=0.039), and average power (r=0.77, p=0.024). For the left leg, however, the only correlation found with the CRD is the average power (r=0.75, p=0.044). Conclusions The medium composite reach distance CRDM is directly correlated with the average lower limb power and relative peak power but due to the small sample size, the power of this effect is unknown. CRDR (right leg) significantly correlates with relative peak power, average power but also with average force whereas CRDL (left leg) only correlates with average power. This does not come as a surprise because all the subjects are right side dominant. There is no significant difference between CRDR and CRDL p&lt;0.001. This is quite important because stability asymmetries of the lower limbs may lead to injury.

ECCENTRIC PEAK TORQUE OF THE KNEE FLEXORS AND EXTENSORS RELATES TO BACKWARD SOMERSAULT HEIGHT IN FEMALE JUNIOR ARTISTIC GYMNASTS

Artistic gymnastics consist of a high amount of jumping actions with rotations around one or more axes. To achieve an optimal flight height to perform the desired number of rotations, the movement pattern and the floor characteristics have to be concerted optimally. To account for the required leg stiffness to utilize the floor’s elasticity, the leg musculature has to generate high forces during the ground contact in an eccentric manner. Thus, eccentric strength of the knee musculature might play an important role for somersault height and run-up velocity in the vault. We investigated the correlation of eccentric peak torque of the knee flexors and extensors and vertical jumping height with backward somersault height and sprinting velocity in female junior artistic gymnasts. The results showed medium to strong, significant correlations between eccentric peak torque and backward somersault height as well as sprinting velocity. Vertical jumping height revealed significant correlations with somersault height and sprinting velocity. Eccentric strength seems to play an important role in joint stiffness regulation to utilize the elastic recoil of gymnastic floors and springboards. In the sprint approaching the vault, the same mechanism seems apparent and is in accordance with findings regarding the sprint in different sports.

Dimensionality Reduction Differentiates Sensitive Force-Time Characteristics from Loaded and Unloaded Conditions throughout Competitive Military Training

The purpose was to evaluate neuromuscular fatigue’s effect on unloaded and loaded countermovement jump (CMJ) force-time characteristics during high-intensity tactical training. Eighteen male and sixteen female Marines completed two maximal effort CMJs, in unloaded (PVC pipe) and loaded (10 kg weight vest and 20 kg barbell) conditions, prior to, and 24, 48, and 72 h after starting the 4-day event. The top three variables from three principal components (PC) were analyzed using mixed-effects modeling (PC1—concentric mean power, eccentric peak force, and modified reactive strength index; PC2—countermovement depth, eccentric mean power, and eccentric mean velocity; PC3—braking duration, jump height, peak power). Metrics from PC1 and PC3 were reduced across training and from both loading conditions. Metrics from PC2 were similarly affected by external loading but were less influenced by training-induced fatigue. Jump performances with the barbell and with shallower countermovement depths did not change throughout training. Thus, 20 kg loaded CMJs are stable neuromuscular measures suitable for tracking chronic training adaptations. Monitoring unloaded and 10 kg loaded CMJ performances, along with movement strategies (i.e., countermovement rates and depth), may help identify moments of accumulated fatigue to inform training and recovery adjustments and improve the sustainability of personnel.

Age-Related Changes in Concentric and Eccentric Isokinetic Peak Torque of the Trunk Muscles in Healthy Older Versus Younger Men

This study investigated age-related changes in trunk muscle function in healthy men and the moderating effect of physical activity. Twelve older (67.3 ± 6.0years) and 12 younger (24.7 ± 3.1years) men performed isokinetic trunk flexion and extension tests across a range of angular velocities (15°/s-180°/s) and contractile modes (concentric and eccentric). For concentric trunk extension, mixed-effects analysis of covariance revealed a significant interaction between Angular velocity × Age group (p = .026) controlling for physical activity. Follow-up univariate analysis of covariance revealed that the younger group produced significantly greater peak torque for all concentric extension conditions. Eccentric trunk strength was somewhat preserved in the older group. Age-related changes in trunk strength were independent of physical activity. The normal loss of trunk muscle strength in older age is muscle- and contractile-mode specific. These findings provide guidance for effective intervention strategies to offset adverse health outcomes related to trunk strength loss in older adults.

Does Footwear Influence Countermovement Jump Parameters Used to Assess Performance in Collegiate Basketball Players?

Background: The countermovement jump (CMJ) is used to monitor short- and long-term changes in neuromuscular performance, where practically relevant alteration may be subtle, requiring detailed and consistent testing protocols to limit error and allow detection of meaningful change. Collegiate basketball players often wear different types of footwear depending upon the training activity, potentially influencing CMJ performance outcomes. Objective: This study evaluated the influence of footwear on key CMJ variables used for routine performance assessments in a cohort of 11 NCAA women’s collegiate basketball players. Method: In a cross-over repeated measures study design, players performed three CMJs in Basketball-, Training-(Trainers), and Olympic Weightlifting (WL) shoes, in a randomized order during one testing session. One-way repeated measures analyses of variance (p ≤ .05) and effect sizes (Cohen’s d) were used to discern differences in CMJ variables among shoe conditions. Results: WL demonstrated greater Eccentric Mean Force (p ≤ .014, d ≥ 0.03) and lower Flight Time:Contraction Time (p ≤ .029, d ≥ 0.31), Jump Height (p ≤ .040, d ≥ 0.32), and Reactive Strength Index-Modified (p ≤ .032, d ≥ 0.40) than both Basketball and Trainers. Additionally, WL exhibited lower Concentric Mean Force (p = .018, d = 0.19), Concentric Mean Power (p = .008, d = 0.29), Eccentric Peak Force (p = .050, d = 0.19), and Flight Time (p = .036, d = 0.31) compared to Trainer. No significant differences and only trivial effects appeared between Basketball and Trainers (p &gt; 0.05, d &lt; 0.1). Conclusion: These findings suggest footwear significantly influences CMJ performance. WL shoes appear to negatively impact CMJ performance; however, Basketball and Trainers appear to exert negligible effects that should allow clinicians and practitioners to feel confident about measurement and data quality when performing short- and long-term CMJ measurements in either Basketball or Trainers.

Effects of Adding Inter-Set Static Stretching to Flywheel Resistance Training on Flexibility, Muscular Strength, and Regional Hypertrophy in Young Men.

Performing static stretching (SS) during resistance training (RT) rest periods is posited to potentiate muscular adaptations, but the literature is scarce on the topic. Thus, the purpose of this study was to investigate the effects of adding inter-set SS to a lower-limb flywheel RT program on joint flexibility, muscular strength, and regional hypertrophy. Sixteen untrained male adults (21 ± 1 y) completed the study, where they performed progressive flywheel bilateral squatting twice a week for 5 weeks. One leg of each participant was randomly allocated to perform SS during the inter-set rest period (RT+SS), while the other leg served as control (RT only). Before and after the intervention, knee flexion range of motion; knee extension isometric, concentric, and eccentric peak torque; 1-repetition maximum; and muscle thickness of the lower-limb muscles were assessed. Following the training period, additional effects were observed for the inter-set SS side on increasing joint flexibility (p < 0.05), whereas the average increase in strength measures was 5.3% for the control side, and 10.1% for the inter-set SS side, however, SS intervention induced significantly greater gains only for knee extension isometric strength, but not for dynamic 1-RM, concentric, and eccentric tests. Hamstrings and gluteus maximus did not hypertrophy with training; increases quadriceps muscle thickness depended on the site/portion analyzed, but no significant difference was observed between legs (average: RT = 7.3%, RT+SS = 8.0%). The results indicate that adding inter-set SS to RT may provide large gains in flexibility, slightly benefits for muscular strength (especially for isometric action), but do not impact muscle hypertrophy in untrained young men.

Eccentric Force-Velocity Characteristics during a Novel Squat Protocol in Trained Rugby Union Athletes-Pilot Study.

Eccentric strength characteristics have been shown to be important factors in physical performance. Many eccentric tests have been performed in isolation or with supramaximal loading. The purpose of this study was to investigate within- and between- session reliability of an incremental eccentric back squat protocol. Force plates and a linear position transducer captured force-time-displacement data across six loading conditions, separated by at least seven days. The reliability of eccentric specific measurements was assessed using coefficient of variation (CV), change in mean, and intraclass correlation coefficient (ICC). Eccentric peak force demonstrated good ICC (≥0.82) and TE (≤7.3%) for each load. Variables based on mean data were generally less reliable (e.g., mean rate of force development, mean force, mean velocity). This novel protocol meets acceptable levels of reliability for different eccentric-specific measurements although the extent to which these variables affect dynamic performance requires further research.

The Effects of Spirulina Supplementation on Redox Status and Performance Following a Muscle Damaging Protocol

Spirulina plantensis is a popular supplement which has been shown to have antioxidant and performance enhancing properties. The purpose of this study was to evaluate the effects of spirulina supplementation on (a) redox status (b) muscle performance and (c) muscle damage following an eccentric bout of exercise that would induce muscle damage. Twenty-four healthy, recreationally trained males participated in the study and were randomly separated into two groups: a spirulina supplementation (6 g per day) and a placebo group. Both groups performed an eccentric bout of exercise consisting of 5 sets and 15 maximum reps per set. Blood was collected at 24, 48, 72 and 96 h after the bout and total antioxidant capacity (TAC) and protein carbonyls (PC) were assessed in plasma. Delayed onset muscle soreness (DOMS) was also assessed at the same aforementioned time points. Eccentric peak torque (EPT) was evaluated immediately after exercise, as well as at 24, 48, 72 and 96 h post exercise. Redox status indices (TAC and PC) did not change significantly at any time point post exercise. DOMS increased significantly 24 h post exercise and remained elevated until 72 h and 96 h post exercise for the placebo and spirulina group, respectively. EPT decreased significantly and immediately post exercise and remained significantly lower compared to baseline until 72 h post exercise. No significant differences between groups were found for DOMS and EPT. These results indicate that spirulina supplementation following a muscle damaging protocol does not confer beneficial effects on redox status, muscle performance or damage.

Effects of a low‐dose Copenhagen adduction exercise intervention on adduction strength in sub‐elite male footballers: A randomised controlled trial

Footballers with weak hip adductors are at increased risk of groin injury, and adductor strengthening has been shown to reduce this risk. However, the minimal effective dose of strength training to improve hip adductor strength and mitigate the risk of adductor problems remains unknown. The aim of this randomised controlled trial was to investigate the training and detraining effects of a low-dose Copenhagen adduction exercise (CA) intervention in sub-elite male footballers on eccentric hip adduction strength (primary outcome) and peak adductor squeeze strength (secondary outcome). Thirty-nine male footballers were randomised into two groups: The intervention group completed the CA twice weekly during six in-season weeks in addition to normal football training, while the control group continued normal football training. Strength testing was performed at weeks 0, 3, 6 (training period), and weeks 7-9 (detraining period). There was no between-group difference in eccentric strength at week 6 and 9. There was a significant group by time interaction at 6 weeks (0.52 Nm/kg, 95% CI 0.17-0.86) and 9 weeks (0.59 Nm/kg, 95% CI 0.25-0.93) at which the intervention group displayed greater adductor squeeze strength. These results suggest the low-dose CA intervention is insufficient to modify eccentric hip adduction strength but improves peak adductor squeeze strength.

Development of a Novel Nordic Hamstring Exercise Device to Measure and Modify the Knee Flexors' Torque-Length Relationship.

The Nordic hamstring exercise (NHE) has been shown to reduce hamstring injury risk when employed in training programs. This study investigates a novel device to modify the NHE torque-length relationship of the knee flexors, as targeting the hamstrings at a more extended length may have benefits for hamstring strain injury prevention and rehabilitation. Eighteen recreational male participants completed three bilateral NHE repetitions at a conventional 0° flat position, a 10° incline, and a 10° decline slope on a novel device (HALHAM°). Measures of peak torque and break-torque angle explored the effect of inclination on the knee flexors' length-tension relationship. Relative thigh-to-trunk angle and angular velocity of the knee joint were used to assess influence of inclination on technique and exercise quality. Break-torque angle increased when performed at an incline (134.1 ± 8.6°) compared to both the decline (112.1 ± 8.3°, p <0.0001, g = 2.599) and standard flat NHE positions (126.0 ± 9.8°, p = 0.0002, g = 0.885). Despite this, altering inclination did not affect eccentric knee flexor peak torque (decline = 132.0 ± 63.1 Nm, flat = 149.7 ± 70.1 Nm, incline = 148.9 ± 64.9 Nm, F = 0.952, p = 0.389), angular velocity of the knee joint at break-torque angle (decline = 23.8 ± 14.4°, flat = 29.2 ± 22.6°, incline = 24.5 ± 22.6°, F = 0.880, p = 0.418) or relative thigh-to-trunk angle at break-torque angle (decline = 20.4 ± 10.4°, flat = 16.7 ± 10.8°, incline = 20.2 ± 11.2°, F = 1.597, p = 0.207). The report recommends the use of arbitrary metrics such as break-torque angle that can be replicated practically in the field by practitioners to assess proxy muscle length changes i.e., the angular range over which the torque can be produced. Inclination of the Nordic hamstring exercise leads to hamstring muscle failure at longer muscle lengths without reductions in the maximal force exuded by the muscle. Therefore, the NHE performed on an incline may be a more effective training intervention, specific to the proposed mechanism of hamstring strain injury during sprinting that occurs whilst the muscle is rapidly lengthening. Using a graded training intervention through the inclinations could aid gradual return-to-play rehabilitation.

Muscle Strength Deficit though Intact Proprioception after Lateral Ankle Sprain without Persistent Instability

Abstract Background Lateral ankle sprain is one of the most common injuries in competitive sports. Previous studies which investigated muscle strength and proprioception (joint position sense) focused on subjects who sustained ankle sprain with instability. It is also important to investigate strength deficits and proprioception in subjects with a history of ankle sprain without instability. Therefore the aim of the study is to investigate proprioception and muscle strength deficits in athletes with lateral ankle sprain. Methods Twenty-four male athletes with a history of lateral ankle sprain and 24 age-matched controls (mean age of 22.42±4.13 years, mean height of 173±5.73 cm, and mean weight of 71.20±7.55 Kg) participated in this cross-sectional study. Peak torque and peak torque ratio at speeds of 30 and 120°/s for concentric and eccentric ankle inversion/eversion were evaluated using an isokinetic dynamometer. The joint position sense of the ankle joint was evaluated using an active angle reproduction test. Result Peak torque produced was significantly less in subjects with history of ankle sprain in concentric inversion 30°/s(t(47)=4.11; p=0.000, Cohen’s d=1.29), concentric inversion 120°/s (t(47)=3.01; p=0.006, Cohen’s d=1.13), concentric eversion 30°/s (t(47)=3.85; p=0.001, Cohen’s d=1.24) and concentric eversion 120°/s (t(47)=3.15; p=0.005, Cohen’s d=1.09). At the same time there was no significant difference observed in eccentric eversion peak torque in both speed (eccentric eversion 30°/s p=0.079; eccentric eversion 120°/s p=0.867) between experimental and control group. No significant difference was found in the joint position sense in the maximal active inversion −5° position (p=0.312) and the 15° inversion position (P=0.386) between both group. Conclusion The study’s results reported a significantly less peak torque of invertors and evertors during concentric movements in athletes with history of ankle sprain. At the same time, no significant difference reported in the evertor/invertor peak torque ratio, and active joint position sense between the 2 groups.

High- vs. Low-Intensity Fatiguing Eccentric Exercise on Muscle Thickness, Strength, and Blood Flow.

Hill, EC, Housh, TJ, Smith, CM, Keller, JL, Schmidt, RJ, and Johnson, GO. High- vs. low-intensity fatiguing eccentric exercise on muscle thickness, strength, and blood flow. J Strength Cond Res 35(1): 33-40, 2021-The purpose of this investigation was to examine the acute effects of equal volumes of fatiguing high- vs. low-intensity eccentric muscle actions on changes in muscle thickness, echo intensity, muscle blood flow, and adipose thickness. Eighteen men (mean ± SD = 23.2 ± 3.0 years) performed eccentric peak torque (PT) and maximal voluntary isometric contraction (MVIC) trials before (pretest), immediately after (posttest), and 5 minutes after (recovery) performing randomly ordered fatiguing eccentric, isokinetic (180°·s-1) muscle actions of the elbow flexors at 40% (72 repetitions) or 80% (36 repetitions) of eccentric PT. Muscle thickness, exercise-induced edema, muscle blood flow, and adipose thickness were also assessed via ultrasound at pretest, posttest, and recovery. There were no intensity-specific effects on the patterns of responses for eccentric PT, MVIC, muscle thickness, echo intensity, muscle blood flow, or adipose thickness. There were, however, effects across time that decreased from pretest to posttest and from pretest to recovery for eccentric PT (21.5 and 13.0%), MVIC (14.6 and 5.8%), and adipose thickness (10.0 and 6.0%), but increased for muscle thickness (7.6 and 5.9%), echo intensity (13.7 and 9.9%), and muscle blood flow (129.6 and 90.1%) (collapsed across 40 and 80%). These findings indicated that when matched for exercise volume, there were no intensity-related effects on the increases in muscle thickness, echo intensity, muscle blood flow, or the decreases in eccentric PT, MVIC, and adipose thickness after fatiguing eccentric muscle actions. Therefore, exercise volume, independent of exercise intensity and number of repetitions, may be a mediating factor of muscle fatigue and performance during eccentric muscle actions.

FLYWHEEL LOW-ROW RESISTANCE EXERCISE AMONG OLDER ADULT WOMEN: A RANDOMIZED CONTROLLED TRIAL

The purpose of our study was to examine the practical application of the progressive resistance exercise protocol among older adult women using a custom-made low-row flywheel (FW) device. The objective was to compare the effects of the FW device exercise protocol to the traditional gravitybased (GB) one, with regards to older adult women's physical abilities, i.e. shoulder mobility, upper body low-row strength, velocity, power and, lastly, trunk extensor endurance. Fourty healthy older adult women (old: 66 ± 5 years; height: 1,62 m; weight: 73,7 kg; body mass index: 28 ± 6 kg/m2 ) were randomly assigned to the FW low-row or Pulley lowrow group. They underwent eight weeks of resistance exercise. We used a two-way ANOVA for repeated measures and standardized effect sizes (ES) comparison to assess exercise-related differences within and between groups. The results showed significant improvement of resistance exercise parameters during the eight-week resistance exercise protocol, regardless of the group. Moreover, we found no statistically important inter-group differences in improvement of shoulder mobility, upper body strength, velocity, power and trunk extensor endurance. Nevertheless, the highest ES in favour of FW low-row group was found when comparing the eccentric peak power changes. We have demonstrated that FW load could be as effective and useful as GB pulley row-row resistance exercise modality. Further research is required, where the concept of the eccentric overload and muscle power enhancement with the use of FW devices for older adult population should be utilized.

The Relationship between Nordic Hamstring Test and Isokinetic Dynamometry in Football and Track and Field Student Athletes: a Cross-Sectional Study

Background: Nordic hamstring test is a field-based test to estimate the hamstrings’ injury risk. The aim of this study was to investigate the relationship between Nordic hamstring test and isokinetic dynamometry in football and track and field student athletes. Methods: Knee flexor eccentric peak torque of hamstring, optimum length, and muscle balance indices were obtained in two seated and lying positions in 22 footballs and 22 track and field student athletes. The Nordic break point angle was also measured. Results: There were significant correlations between isokinetic dynamometry indices and breakpoint angles (P=0.000). Best predictors of break point angle were muscle balance indices and eccentric hamstring peak torques in lying position (P<0.05). Conclusion: It seems that Nordic hamstring test is related to isokinetic dynamometry. This relationship is also dependent on the hip joint positioning. These findings may have implications in the assessment of athletic performance.