Discipline-specific Torque-Velocity Profiles and Musculotendinous Morphology in Athletes.

OBJECTIVES: The aim of this study was to compare torque-velocity profiles, muscle architecture, tendon dimensions, and bilateral-symmetry between competitive cyclists (CY), competitive runners (RN), ice-hockey players (IH), basketball players (BP), and physically-active individuals (CN) (n=10 for each group). METHODS: Vastus lateralis (VL) muscle and patellar tendon (PT) structures were determined with B-mode ultrasonography, and maximal knee extensor isokinetic torque was assessed at three different velocities. RESULTS: Optimal torque and velocity were lower in runners than CY, BP and IH (p<0.05). Maximal power was similar between the athlete groups but greater than CN (p<0.05). Furthermore, RN and BP reached their peak-torque at longer muscle lengths compared to IH and CY (p<0.05). RN had the lowest VL muscle thickness and the greatest fascicle length, while CY had the greatest pennation angle (p<0.05). CY had the greatest PT thickness, particularly at the proximal and medial sites, while BP at the distal point (p<0.05), with similar trends observed for PT cross-sectional-area. CONCLUSIONS: Our findings show that even if power generating capacity is similar between athletic disciplines, there are discipline-specific muscle adaptations, where particularly runners appear to have muscles adapted for speed rather than torque development, while in cyclists, velocity is sacrificed for torque development.

Obesity-related reduced spirometry and altered breathing pattern are associated with mechanical disadvantage of the diaphragm.

The aim of this study was to characterize the breathing patterns of individuals with obesity during routine activities such as sitting and standing, and to identify potential contributors to alterations in these patterns. Measurements performed in 20 male subjects with obesity (BMI, 31.8±1.5 kg/m2) and 20 controls (BMI, 23.5±1.4 kg/m2) included anthropometric parameters, breathing-patterns in sitting and standing positions, spirometry, maximal respiratory pressures, and diaphragm B-mode ultrasonography. Individuals with obesity exhibited lower tidal volume and increased respiratory rate to maintain a similar minute-ventilation (p<0.05). Subjects with obesity demonstrated impaired spirometry and respiratory muscle strength, with inspiratory functions being notably compromised (p<0.05). Individuals with obesity had a greater diaphragm thickness at end inspiration but lower thickening-fraction at end quiet and forced breathings and reduced diaphragmatic displacement and excursion during maximal breaths (p<0.05). BMI was negatively associated with all respiratory function markers (p<0.05). Individuals with obesity exhibit a higher respiratory rate but lower tidal volume, likely to accommodate decreased compliance and excess thoracic and abdominal fat, further hindering inspiratory function. Moreover, increased adiposity is associated with a thicker but weaker diaphragm, primarily due to the diaphragm's mechanical disadvantage rather than its intrinsic inability to generate force.

Hamstring stiffness and injury risk factors during the handball season in female players.

Monitoring the muscle mechanical properties and functions of female athletes throughout their training season is relevant to understand the relationships between these factors and to predict noncontact injuries, which are prevalent among female athletes. The first aim of this study was to determine whether female handball players' passive stiffness of the hamstring muscles is associated with hamstring extensibility, strength of knee flexors and extensors, and lower limb stiffness. Additionally, the study monitored fluctuations in these factors over 25 weeks. The study utilized an isokinetic dynamometer to record hamstring passive stiffness, extensibility, and hamstring and quadriceps strength of 18 young handball players. Lower limb stiffness was determined from a countermovement vertical jump conducted on a force plate. The countermovement jump involved the calculation of the peak force during the eccentric phase and the mean force during the concentric phase. The results showed a positive correlation between hamstring passive stiffness and lower limb stiffness (r = 0.660, p < 0.01), knee flexion and extension strength (r = 0.592, p < 0.01 and r = 0.497, p < 0.05, respectively), and eccentric peak force (r = 0.587, p < 0.01) during jumping. The strength of knee extensors increased significantly after 6 weeks, and hamstring stiffness after 12 weeks of training. In conclusion, the increased hamstring stiffness following training did not match other factors associated with injury risk. Therefore, preventing multifactorial injury risk requires a comprehensive approach, and monitoring one factor alone is insufficient to predict noncontact injuries in female handball players.

The effects of high-velocity hamstring muscle training on injury prevention in football players.

Background: Explosive and fast body movements, sprints, jumps and quick changes of direction, which are characteristic of the football training, place considerable strain on the hamstring muscles. Due to the high occurrence of hamstring injuries, new preventive strategies are required that focus on high-velocity training. The purpose was to assess the effectiveness of high-velocity elastic-band training in reducing the occurrence of hamstring injuries in football players. Methods: Male football players from 15 teams (n = 319) playing in national competitions participated in this study. The players were involved in a 5-week exercise period in either the intervention group (INT) or the control group (CON), with a follow-up period of ∼4 months where hamstring injuries and exposure time were recorded. The INT group had two to three sessions per week of elastic-band training with low-load, high-velocity leg curls while lying prone; the CON group performed self-paced football-specific drills. Results: The incidence rate of hamstring injuries was 6.5% in the INT group (8 out of 123 players) and 9.2% in the CON group (18 out of 196 players). Although the INT group showed almost 1/3 reduction in hamstring injury incidence compared to the CON group, the difference was not statistically significant (p > 0.05). Moreover, no differences (p > 0.05, odds ratio [OR] = trivial-to-small) in distribution between the groups were found in hamstring injury characteristics (leg dominance and mechanism) except for the distribution of injuries that occurred during matches or training (p = 0.036; OR = 6.14, moderate). Conclusion: The program of high-velocity elastic-band training did not prove to be effective in preventing hamstring muscle injuries in football players despite displaying some positive indications that could be considering when creating injury prevention programs.

Riding a Mechanical Scooter from the Inconvenient Side Promotes Muscular Balance Development in Children.

Mechanical scooter riding is a popular physical activity among children, but little is known about the differences in muscle loading between the dominant and non-dominant sides during this activity. The objective of this study was to identify the muscle activation patterns in children's dominant and non-dominant legs as they rode scooters on the convenient and inconvenient sides. The study included nine healthy children aged 6-8. The participants rode 20 m on a mechanical scooter at a self-selected pace using both the convenient and inconvenient sides. Electromyography was used to measure the muscle activity in the dominant and non-dominant legs during the pushing and gliding phases. A 20 m sprint run was used as a control exercise to estimate the typical differences in muscle activation between the dominant and non-dominant legs. In the pushing phase, the symmetry index for five of the eight analyzed muscles exceeded 50% (p < 0.05); four of these muscles were more active in the pushing leg, and one was more active in the standing leg. In the gliding phase, four muscles were more active in the standing leg, and one was more active in the pushing leg (p < 0.05). Upon observing children who changed sides while riding a scooter, it was found that the pattern of muscle activation displayed a reverse trend that resembled the initial pattern. Our study indicated notable differences in muscle activity patterns between the dominant and non-dominant sides of individual leg muscles during children's scooter riding. These patterns were reversed when children switched sides on the scooter. These findings suggest that using both legs and switching sides while riding a scooter may be a viable strategy for promoting balanced muscular development.

Relationships between muscle quality, subcutaneous adipose tissue, and sprint performance markers of competitive cyclists.

BACKGROUND: Many variables are considered to be determinants of cycling sprint performance. Among them, the importance of skeletal muscle properties in relation to cycling performance has been consistently underlined. The aim of the present study was to evaluate the vastus lateralis (VL), rectus femoris (RF) and vastus medialis (VM), echo intensity (EI) and subcutaneous adipose tissue (SAT) content in a group of competitive cyclists and to identify whether these are related to sprint performance. METHODS: Muscle echo intensity was evaluated by ultrasound in 16 highly trained competitive cyclists. The cyclists performed a maximal-intensity sprint session comprising four 15 s maximal sprints on a Wingate bike with 2 min of recovery between each. Pearson correlational analysis with linear regression was used to identify significant relationships between the criteria EI and SAT content and the sprint performance variables. RESULTS: Muscle EI correlated strongly with sprint performance markers (r=from 0.54 to 0.62; P<0.05), while SAT content and body fat percentage correlated trivially to moderately with sprint performance (r=from 0.07 to 0.40; P>0.05). CONCLUSIONS: Overall, muscle quality of knee extensors was positively related to sprint performance markers, but SAT content was not. Although additional studies are needed, muscle quality may represent a valid body composition indicator and may be helpful for supporting sprint performance optimization procedures in competitive cyclists.

Associations between Muscle-Tendon Morphology and Functional Movements Capacity, Flexibility, and Balance in Older Women.

Loss of functional movement capacity in older adults is related to adverse changes in musculotendinous morphology, but this relationship is poorly understood. This study examined the associations between musculotendinous morphology and functional movements, flexibility, and balance ability. Ninety-nine older women (66.6 ± 4.6 years, body mass index 23.5 ± 3.3 kg∙m−2) were recruited from Chonburi Province, Thailand. During one 90-min visit, muscle ultrasound imaging of vastus lateralis, biceps femoris, and medial gastrocnemius muscles, and tendon ultrasonography of the Achilles tendon and patellar tendon were performed. Measures were also obtained for the straight leg raise, passive dorsiflexion, balance, and functional tests (Five Times Sit to Stand (5TSTS), Timed Up and Go (TUG), 10-Meter Fast Walk Test (10-MFWT), and 6-Minute Walk Test (6-MWT)). The results specify that functional movement performance correlates most strongly with medial gastrocnemius muscle thickness (5TSTS (r = −0.26), TUG (r = −0.44), 10-MFWT (r = 0.41), and 6-MWT (r = 0.48) all p < 0.05) and that vastus lateralis muscle thickness and medial gastrocnemius muscle thickness correlate positively with balance ability (r = 0.24, 0.34; p < 0.05) and negatively with fear of falling. It appears that muscle mass, rather than other morphological parameters, such as muscle quality or fascicle length, is the main factor affecting the susceptibility of older women to frailty.

Differences in Knee Extensors' Muscle-Tendon Unit Passive Stiffness, Architecture, and Force Production in Competitive Cyclists Versus Runners.

To describe the possible effects of chronic specific exercise training, the present study compared the anthropometric variables, muscle-tendon unit (MTU) architecture, passive stiffness, and force production capacity between a group of competitive cyclists and runners. Twenty-seven competitive male cyclists (n = 16) and runners (n = 11) participated. B-mode ultrasound evaluation of the vastus lateralis muscle and patellar tendon as well as passive stiffness of the knee extensors MTU were assessed. The athletes then performed a test of knee extensor maximal voluntary isometric contractions. Cyclists displayed greater thigh girths, vastus lateralis pennation angle and muscle thickness, patellar tendon cross-sectional area, and MTU passive stiffness than runners (P < .05). Knee extensor force production capacity also differed significantly, with cyclists showing greater values compared with runners (P < .05). Overall, the direct comparison of these 2 populations revealed specific differences in the MTU, conceivably related to the chronic requirements imposed through the training for the different disciplines.

The role of age on neuromuscular performance decay induced by a maximal intensity sprint session in a group of competitive endurance athletes.

Age-related changes in the neuromuscular system functions may affect profoundly high-level athletes' performance across their careers. The present study aimed to analyse the fatiguing effect of a maximal intensity sprint session (MISS) on competitive athletes of different ages. Thirty-one competitive endurance athletes completed a knee extensors and flexors' maximal-voluntary-isometric-contraction (MVC) test before and after a maximal-intensity-sprint-session (MISS) consisting of 4x15s Wingate-tests. The data have been stratified considering three age categories (18-28, n=11, 29-38; n=10; 39-43, n=10). Overall, both quadricep and hamstring muscles early and late rate of torque development (RTD) dropped significantly more than the maximal voluntary torque (MVT) (p<.05). Age had a significant effect on early RTD, with older athletes exhibiting greater RTD (p<.05). A significant effect of age also emerged for the changes in surface sEMG variables, in which the frequency spectrum variables dropped significantly more than the sEMG amplitude (RMS) (p<.05). The dynamics of changes in neuromuscular performance markers after a MISS suggested that getting older competitive athletes may potentially experience a greater loss in early explosive strength compared to maximal or late explosive strength.

Warm-Up and Hamstrings Stiffness, Stress Relaxation, Flexibility, and Knee Proprioception in Young Soccer Players.

CONTEXT: Nerves or fascia may limit motion in young soccer players, thereby contributing to frequent hamstrings injuries. Nerve-gliding exercises and self-myofascial release techniques may enhance range of motion (ROM). OBJECTIVE: To compare the immediate effect of foam rolling (FR) and neurodynamic nerve gliding (NDNG) on hamstrings passive stiffness, viscoelasticity, flexibility, and proprioception during the warm-up of soccer players. DESIGN: Crossover study. SETTING: Research laboratory. PATIENTS OR OTHER PARTICIPANTS: A total of 15 male soccer players (age = 18.0 ± 1.4 years, height = 183.1 ± 6.0 cm, mass = 76.9 ± 7.8 kg) on the same team. INTERVENTION(S): The FR and NDNG consisted of 6 sets of 45 seconds with a 15-second rest between sets. Over a 2-week period, participants performed FR and NDNG on 2 separate occasions. MAIN OUTCOME MEASURE(S): Stiffness (between 50% and 80%, and 85% and 95% [STFmax] of maximal knee-extension ROM), viscoelasticity (stress-relaxation test), knee-extension ROM, hamstrings passive-resistance torque (PRT), hip-flexion angle (straight-leg raise test), and active knee-joint position sense. RESULTS: We observed an interaction between time and intervention for STFmax (F1,17 = 5.024, P = .042), knee-extension ROM (F1,17 = 7.371, P = .02), and PRT (F1,17 = 4.876, P = .044). The NDNG technique induced increases in STFmax (t17 = 2.374, P = .03), ROM (t17 = 2.843, P = .01), and PRT (t17 = 2.982, P = .008). Both NDNG and FR led to improved performance on the straight-leg raise test (F1,17 = 87.514, P < .001). No interaction or main effect was found for the stress-relaxation test or active knee-joint position sense. CONCLUSIONS: Adding NDNG to the warm-up routine increased ROM more than FR and may benefit soccer players.

Response of Knee Extensor Muscle-Tendon Unit Stiffness to Unaccustomed and Repeated High-Volume Eccentric Exercise.

The purposes of this study were to investigate the muscle-tendon unit stiffness response and to compare the stiffness with those of other indirect markers induced by two bouts of unaccustomed eccentric exercise. Eleven untrained men performed two bouts of 200 maximal eccentric contractions of the right quadriceps 4 weeks apart. Changes in stiffness, pain evoked by stretching and pressure, plasma creatine kinase (CK) activity, and muscle thickness were followed for 7 days after each bout. Stiffness and pain peaked immediately and 1 day after the first exercise bout, whereas CK and thickness were highest 4 and 7 days after the first exercise bout, respectively (p < 0.05 for all). Muscular pain, thickness, and stiffness responses were lower by 53.3%, 99%, and 11.6%, respectively, after the repeated bout compared to after the first bout (p < 0.05 for all), while CK activity response did not differ significantly between bouts. High responders for an increase in muscle-tendon unit stiffness showed a repeated-bout effect for stiffness, pain, and CK activity (by 29%, 65%, and 98%, p < 0.05 for all), but the repeated-bout effect was not that clear in low responders. These findings suggest that a repeated eccentric exercise bout effect on stiffness in quadriceps is mostly not associated with muscle pain and CK activity, but there are large individual differences.

Effect of high volume stretch-shortening cycle exercise on vertical leg stiffness and jump performance.

The study aims were to investigate the effects of muscle damage induced by high-volume stretch-shortening cycle exercise on countermovement jump (CMJ) performance and vertical leg stiffness during squat and landing phases. Changes in the peak torque of knee extensor muscles, soreness, plasma CK activity, vertical leg stiffness, and CMJ characteristics were measured in recreationally active men after 50, 100, 150 and 200 drop jumps (DJs) and again 24 h later. The isometric voluntary peak torque after 50 DJs decreased by 22 ± 12% (p < 0.01). However, during the squat phase of CMJ eccentric peak power and rate of force development together with the concentric mean force during the push-off phase increased after 50 DJs (all p < 0.05). After 200 DJs, jump height and concentric peak power during push-off were decreased (p < 0.05). At 24 h after exercise, jump height, peak eccentric force, the rate of eccentric force development and the mean concentric force in CMJ and vertical leg stiffness in the squat all remained decreased (p < 0.05), while vertical leg stiffness in the landing phase was increased (p < 0.05). Muscle damaging exercise volume is associated with changes in vertical leg stiffness and CMJ performance.

Effect of Training and Match Loads on Hamstring Passive Stiffness in Professional Soccer Players.

OBJECTIVE: the purpose of this study was to identify differences in hamstring passive stiffness between the pre-season and in-season periods. METHODS: Hamstring strength and passive stiffness were measured in professional male soccer players before and after the pre-season (4 weeks), and after the in-season (6 weeks) periods using an isokinetic dynamometer. Muscle passive stiffness was determined from the slope of the passive torque-angle relationship. External loads (acceleration and jumps) were monitored by GPS and internal loads by questionnaire. RESULTS: Hamstring passive stiffness increased after 10 weeks of training and matches, without changes in passive peak torque and range of motion. The hamstring passive stiffness modifications were associated with the volume and intensity of accelerations and jumps. The individual data analysis also provided some support for the suppression of the biomechanical adaptation in the subjects with relatively large external load. CONCLUSIONS: Regular training and match workouts increase hamstring passive stiffness in professional soccer players but the adaptation of muscle-tendon unit passive elements might not occur if players experience excessive mechanical stress.

Immediate effects of neurodynamic nerve gliding versus static stretching on hamstring neuromechanical properties.

PURPOSE: We investigated the immediate effects of neurodynamic nerve gliding (ND) on hamstring flexibility, viscoelasticity, and mechanosensitivity, compared with traditional static stretching (ST). METHODS: Twenty-two physically active men aged 21.9 ± 1.9 years were divided randomly into two equal intervention groups using ST or ND. An isokinetic dynamometer was used to measure the active knee joint position sense, perform passive knee extension, record the passive extension range of motion (ROM) and the passive-resistive torque of hamstrings. Stiffness was determined from the slope of the passive torque-angle relationship. A stress relaxation test (SRT) was performed to analyze the viscoelastic behavior of the hamstrings. The passive straight leg raise (SLR) test was used to evaluate hamstring flexibility. RESULTS: A significant interaction was observed for ROM and passive ultimate stiffness, reflected by an increase in these indicators after ND but not after SD. SLR increased significantly in both groups. After ST, a significantly faster initial stress relaxation was observed over the first 4 s. than after ND. There was no significant change in the active knee joint position sense. CONCLUSIONS: ND provided a slightly greater increase in hamstring extensibility and passive stiffness, possibly by decreasing nerve tension and increasing strain in connective tissues than ST. The ST mostly affected the viscoelastic behavior of the hamstrings, but neither intervention had a significant impact on proprioception.

Low frequency fatigue and changes in muscle fascicle length following eccentric exercise of the knee extensors.

NEW FINDING: What is the central question of this study? Does low frequency muscle fatigue indicate a failure of excitation-contraction coupling after eccentric exercise, or is it simply due to a change in muscle length? What is the main finding and its importance? The low to high frequency muscle fatigue ratio was relatively insensitive to changes in muscle length, and any changes in length following eccentric exercise were far too small to account for the high degree of low frequency fatigue. The results strengthen the suggestion that the early loss of force following eccentric exercise is due to a deficit of excitation-contraction coupling. ABSTRACT: Development of long lasting fatigue (low frequency fatigue; LFF), assessed as the ratio of forces at 20 and 100 Hz stimulation, suggests the early phase of muscle damage caused by eccentric exercise is due to a deficit of excitation-contraction coupling. However, this could be caused by a change of muscle length. Eleven men (21.3 ± 2.0 years) performed 200 maximum eccentric knee extensions (30-110 deg flexion). Force generated by 20 and 100 Hz stimulation and maximum isometric force (MIF) were determined at knee angles 50, 70 and 90 deg before and immediately after the exercise. Vastus lateralis fascicle length (FL) was measured by ultrasound of resting and contracting muscle. Peak MIF (829 ± 119 N) was at 70 deg knee flexion, falling to 486 ± 180 N (P < 0.001) after exercise, but with no change in optimum angle. FLs at rest were unaffected by eccentric exercise, but during contraction they were on average 8.8% (95% CI: 4.1, 13.5%, P = 0.002) longer after exercise. Before exercise, the 20/100 ratio increased with muscle length, from 0.69 ± 0.09 at 50 deg, 0.72 ± 0.05 at 70 deg and 0.80 ± 0.08 at knee angle 90 deg (P < 0.001). After eccentric exercise the 20/100 ratio was reduced to 0.29 ± 0.08 at 50 deg, 0.27 ± 0.04 at 70 deg and 0.34 ± 0.04 at 90 deg (P < 0.001). The 20/100 ratio was relatively insensitive to changes in muscle length and the decrease following eccentric exercise was far greater than might be caused by any changes in muscle length after eccentric exercise. The results show that LFF following eccentric exercise is not due to change in muscle length and strengthen the suggestion that it represents a deficit in excitation-contraction coupling.

High-velocity elastic-band training improves hamstring muscle activation and strength in basketball players.

BACKGROUND: The aim of this study was use surface EMG activity to assess changes in co-activation of knee flexors and extensors muscle groups during elastic-band exercise after 5 weeks of high-velocity elastic-band training in basketball players. METHODS: College male basketball players (N.=18) were randomly divided into one of two groups: 1) the elastic-band training group performed low-load and high-velocity - lying prone - hamstring curls training three times per week; 2) the control group did not do any training. Pre- and post- training assessment included concentric knee extension and flexion at 60°/s and 240°/s, and the frequency of knee flexion and extension with elastic bands in the prone position. The EMG of the rectus femoris, semitendinosus muscles and the long head of the biceps femoris were assessed during these activities, and 30-m sprint running speed was measured from a stationary start and a running start. RESULTS: It was shown that high-velocity elastic-band training was 1) feasible, 2) increased movement velocity and 3) muscle strength, 4) altered neural control such that excessive lengthening of the hamstring muscle, and hence strain-injuries, may be prevented and 5) improved sprint performance in basketball players. CONCLUSIONS: These results suggest that high-velocity elastic-band training may be a tool to prevent hamstring strain-injuries in basketball players.

Slow torque recovery after eccentric exercise and the repeated bout effect; the role of primary and secondary muscle damage.

OBJECTIVES: To determine the role of primary and secondary damage in the variation between people of maximum voluntary contraction (MVC) torque recovery following eccentric exercise and the faster recovery following a repeated bout of exercise. METHODS: Twenty-one healthy, active but untrained young female subjects undertook eccentric exercise of the elbow flexors and 11 repeated the exercise 28 days later. Changes of MVC torque and creatine kinase (CK) were followed for 7 days after each bout of exercise. RESULTS: Following the first bout, 45% of subjects showed a continuing decline in MVC torque, suggesting secondary damage, which was correlated with a large delayed CK release (R2=0.54, p<0.001). After the second bout of exercise, the initial MVC torque loss was similar to that after the first bout while torque recovery was faster, but only for the previously slow recovering subjects. Comparing the time course of MVC torque recovery of first and second bouts suggests secondary damage develops over 4 days. CONCLUSIONS: The data are consistent with primary damage being similar between subjects and unaffected by the repeated bout while it is secondary damage which accounts for differences in MVC torque recovery and is suppressed following a repeated bout of exercise.

Effects of myostatin on the mechanical properties of muscles during repeated active lengthening in the mouse.

The aim of the present study was to investigate how myostatin dysfunction affects fast and slow muscle stiffness and viscosity during severe repeated loading. Isolated extensor digitorum longus (EDL) and soleus muscles of young adult female mice of the BEH (dysfunctional myostatin) and BEH+/+ (functional myostatin) strains were subjected to 100 contraction-stretching loading cycles during which contractile and mechanical properties were assessed. BEH mice exhibited greater exercise-induced muscle damage, although the effect was muscle- and age-dependent and limited to the early phases of simulated exercise. The relative reduction of the EDL muscle isometric force recorded during the initial 10-30 loading cycles was greater in BEH mice than in BEH+/+ mice and exceeded that of the soleus muscle of either strain. The induced damage was associated with lower muscle stiffness. The effects of myostatin on the mechanical properties of muscles depend on muscle type and maturity.

Early anterior knee pain in male adolescent basketball players is related to body height and abnormal knee morphology.

OBJECTIVES: To compare knee torque, range of motion, quality of movement, and morphology in dominant and nondominant legs of male adolescent basketball players with and without anterior knee pain and untrained peers. DESIGN: Cross-sectional. SETTING: Sports performance laboratory. PARTICIPANTS: Male basketball players aged 14-15 years with and without anterior knee pain and healthy untrained subjects (n = 88). MAIN OUTCOME MEASURES: Basketball players were allocated to a symptomatic or asymptomatic group based on self-reported anterior knee pain. Associations between pain and body mass, height, passive range of motion, muscle peak torque, coactivation, neuromuscular control, proprioception, and ultrasound observations were investigated. RESULTS: The prevalence of pain did not differ significantly between sides. Of 176 knees inspected, 44 were painful, and 26 of these exhibited abnormalities in ultrasonography. Symptomatic players were 5.0 and 6.9 cm taller than asymptomatic players and controls, respectively (P < 0.05). In athletes with knee pain, the odds ratios of morphological abnormalities and greater height were increased by 8.6 and 5.0 times (P < 0.001). CONCLUSION: Knee pain prevalence in adolescent basketball players was not related to differences between sides but was higher in tall players. Knee pain was accompanied by morphological abnormalities detected with ultrasound.

Serum brain-derived neurotrophic factor and interleukin-6 response to high-volume mechanically demanding exercise.

INTRODUCTION: The aim of this study was to follow circulating brain-derived neurotrophic factor (BDNF) and interleukin-6 (IL-6) levels in response to severe muscle-damaging exercise. METHODS: Young healthy men (N = 10) performed a bout of mechanically demanding stretch-shortening cycle exercise consisting of 200 drop jumps. Voluntary and electrically induced knee extension torque, serum BDNF levels, and IL-6 levels were measured before and for up to 7 days after exercise. RESULTS: Muscle force decreased by up to 40% and did not recover by 24 hours after exercise. Serum BDNF was decreased 1 hour and 24 hours after exercise, whereas IL-6 increased immediately and 1 hour after but recovered to baseline by 24 hours after exercise. IL-6 and 100-Hz stimulation torque were correlated (r = -0.64, P < 0.05) 24 hours after exercise. DISCUSSION: In response to acute, severe muscle-damaging exercise, serum BDNF levels decrease, whereas IL-6 levels increase and are associated with peripheral fatigue. Muscle Nerve 57: E46-E51, 2018.