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Background: The prevalence of anterior cruciate ligament (ACL) injuries increases during maturation and peaks during late adolescence. Previous studies suggested an age-related association between participation in injury prevention programs and reduction of ACL injury. However, few studies have investigated differences in biomechanical changes after injury prevention programs between preadolescent and adolescent athletes. Purpose/Hypothesis: The purpose was to investigate the influence of age on the effects of the FIFA Medical and Research Centre (F-MARC) 11+ injury prevention warm-up program on differences in biomechanical risk factors for ACL injury between preadolescent and adolescent female soccer players. It was hypothesized that the ACL injury risk factors of knee valgus angle and moment would be greater at baseline but would improve more after training for preadolescent athletes than adolescent athletes. It was further hypothesized that flexor-extensor muscle co-contraction would increase after training for both preadolescent and adolescent athletes. Study Design: Controlled laboratory study. Methods: Institutional Review Board–approved written consent was obtained for 51 preadolescent female athletes aged 10 to 12 years (intervention: n = 28, 11.8 ± 0.8 years; control: n = 23, 11.2 ± 0.6 years) and 43 adolescent female athletes aged 14 to 18 years (intervention: n = 22, 15.9 ± 0.9 years; control: n = 21, 15.7 ± 1.1 years). The intervention groups participated in 15 in-season sessions of the F-MARC 11+ program 2 times per week. Pre- and postseason motion capture data were collected during 4 tasks: preplanned cutting, unanticipated cutting, double-legged jump, and single-legged jump. Lower extremity joint angles and moments were estimated through biomechanical modeling. Knee flexor-extensor muscle co-contraction was estimated from surface electromyography. Results: At baseline, preadolescent athletes displayed greater initial contact and peak knee valgus angles during all activities when compared with the adolescent athletes, but knee valgus moment was not significantly different between age groups. After intervention training, preadolescent athletes improved and decreased their initial contact knee valgus angle (–1.24° ± 0.36°; P = .036) as well as their peak knee valgus moment (–0.57 ± 0.27 percentage body weight × height; P = .033) during the double-legged jump task, as compared with adolescent athletes in the intervention. Compared with adolescent athletes, preadolescent athletes displayed higher weight acceptance flexor-extensor muscle co-contraction at baseline during all activities (P < .05). After intervention training, preadolescent athletes displayed an increase in precontact flexor-extensor muscle co-contraction during preplanned cutting as compared with adolescent intervention athletes (0.07 ± 0.02 vs –0.30 ± 0.27, respectively; P = .002). Conclusion: The F-MARC 11+ program may be more effective at improving some risk factors for ACL injury among preadolescent female athletes than adolescent athletes, notably by reducing knee valgus angle and moment during a double-legged jump landing. Clinical Relevance: ACL prevention programs may be more effective if administered early in an athlete’s career, as younger athletes may be more likely to adapt new biomechanical movement patterns. [ABSTRACT FROM AUTHOR]

Background: Anterior cruciate ligament (ACL) injuries are common, and children as young as 10 years of age exhibit movement patterns associated with an ACL injury risk. Prevention programs have been shown to reduce injury rates, but the mechanisms behind these programs are largely unknown. Few studies have investigated biomechanical changes after injury prevention programs in children. Purpose/Hypothesis: To investigate the effects of the F-MARC 11+ injury prevention warm-up program on changes to biomechanical risk factors for an ACL injury in preadolescent female soccer players. We hypothesized that the primary ACL injury risk factor of peak knee valgus moment would improve after training. In addition, we explored other kinematic and kinetic variables associated with ACL injuries. Study Design: Controlled laboratory study. Methods: A total of 51 female athletes aged 10 to 12 years were recruited from soccer clubs and were placed into an intervention group (n = 28; mean [±SD] age, 11.8 ± 0.8 years) and a control group (n = 23; mean age, 11.2 ± 0.6 years). The intervention group participated in 15 in-season sessions of the F-MARC 11+ program (2 times/wk). Pre- and postseason motion capture data were collected during preplanned cutting, unanticipated cutting, double-leg jump, and single-leg jump tasks. Lower extremity joint angles and moments were estimated using OpenSim, a biomechanical modeling system. Results: Athletes in the intervention group reduced their peak knee valgus moment compared with the control group during the double-leg jump (mean [±standard error of the mean] pre- to posttest change, -0.57 ± 0.27 %BW×HT vs 0.25 ± 0.25 %BW×HT, respectively; P = .034). No significant differences in the change in peak knee valgus moment were found between the groups for any other activity; however, the intervention group displayed a significant pre- to posttest increase in peak knee valgus moment during unanticipated cutting (P = .044). Additional analyses revealed an improvement in peak ankle eversion moment after training during preplanned cutting (P = .015), unanticipated cutting (P = .004), and the double-leg jump (P = .016) compared with the control group. Other secondary risk factors did not significantly improve after training, although the peak knee valgus angle improved in the control group compared with the intervention group during unanticipated cutting (P = .018). Conclusion: The F-MARC 11+ program may be effective in improving some risk factors for an ACL injury during a double-leg jump in preadolescent athletes, most notably by reducing peak knee valgus moment. Clinical Relevance: This study provides motivation for enhancing injury prevention programs to produce improvement in other ACL risk factors, particularly during cutting and single-leg tasks. [ABSTRACT FROM AUTHOR]

Background: Musculoskeletal injuries are the most common complaint in active populations. More than 50% of all injuries in sports can be classified as sprains, strains, ruptures, or breaks of musculoskeletal tissues. Nutritional and/or exercise interventions that increase collagen synthesis and strengthen these tissues could have an important effect on injury rates. Objective: This study was designed to determine whether gelatin supplementation could increase collagen synthesis. Design: Eight healthy male subjects completed a randomized, doubleblinded, crossover-design study in which they consumed either 5 or 15 g of vitamin C-enriched gelatin or a placebo control. After the initial drink, blood was taken every 30 min to determine amino acid content in the blood. A larger blood sample was taken before and 1 h after consumption of gelatin for treatment of engineered ligaments. One hour after the initial supplement, the subjects completed 6 min of rope-skipping to stimulate collagen synthesis. This pattern of supplementation was repeated 3 times/d with $ 6 h between exercise bouts for 3 d. Blood was drawn before and 4, 24, 48, and 72 h after the first exercise bout for determination of amino-terminal propeptide of collagen I content. Results: Supplementation with increasing amounts of gelatin increased circulating glycine, proline, hydroxyproline, and hydroxylysine, peaking 1 h after the supplement was given. Engineered ligaments treated for 6 d with serum from samples collected before or 1 h after subjects consumed a placebo or 5 or 15 g gelatin showed increased collagen content and improved mechanics. Subjects who took 15 g gelatin 1 h before exercise showed double the amino-terminal propeptide of collagen I in their blood, indicating increased collagen synthesis. Conclusion: These data suggest that adding gelatin to an intermittent exercise program improves collagen synthesis and could play a beneficial role in injury prevention and tissue repair. [ABSTRACT FROM AUTHOR]

The article discusses research which was conducted to investigate the effect of cluster sets and traditional sets on plyometric jump power (PW), ground reaction force, take-off velocity (TOV), and jump height (JH). Researchers evaluated 26 college men. They found that cluster sets allowed for greater maintenance of PW, TOV, and JH than traditional training sets.

The article presents a study on the effect that supervised exercise with a personal trainer (PTr) has on the development of lean body mass (LBM) and health-related fitness of health club members, as compared to self-directed training. Topics include muscle strength and power, body composition, and aerobic capacity (Vo2max).

The article presents a study which examined the influence of a hip-focused training program on lower extremity biomechanics during a drop-jump activity and its effects in preventing anterior cruciate ligament (ACL) injury in women. In the study, the optimum isometric strength of the hip extensors, hip abductors and knee extensors were evaluated. Based on the results, ACL injury prevention programs focusing on hip muscle performance are effective in preventing ACL injury in women.

The article looks at a study of counter movement jumping performance in competitive runners wearing graduated compression tights or running shorts before and after sessions of submaximal treadmill running. The subjects were monitored for heart rate during the tests. Analysis of jumping height and rating of perceived exertion (RPE) and comfort of the subjects indicated that those wearing graduated compression tights maintained greater lower limb muscle power.

The article looks at the effect of various athletic footwear types on vertical jump and landing performance in male and female athletes. Subjects were evaluated for relative peak power in vertical, depth, and Bosco test jumps while wearing tennis shoes, minimalist footwear, or bare feet. The results indicated higher jump performance in bare feet or minimalist footwear without changes in impact forces.

The article reports a study which was conducted to examine whether muscle co-contraction and tibiofemoral compressive forces in women after undergoing anterior cruciate ligament reconstruction (ACLR) can be reduced through the use of a landing strategy that emphasizes greater hip and knee flexion. The results suggest that tibiofemoral compressive forces and muscle co-contraction can be reduced by use of a landing strategy that emphasizes greater hip and knee flexion.

The article discusses research investigating the influence of rest intervals following assisted jumping on bodyweight (BW) vertical jump performance. The team recruited 20 healthy, recreationally-trained men approximately 23 years. The subjects executed one set of five consecutive assisted jumps following a warm-up period, rested, then performed three BW jumps without assistance. Results of an analyses of variance revealing a main effect for takeoff velocity after rest are discussed.

The article reports on research conducted to investigate the effects self selected music (SSM) and no music (NM) had on the mood and performance of athletes performing bench presses and squat jumps. Researchers evaluated 20 resistance trained college males. They found that there was increased performance during an explosive exercise and an altered mood state when listening to SSM and that listening to SSM might be beneficial for acute power performance.

The purpose of this study was to develop and validate a regression equation to estimate peak power (PP) using a large sample of athletic youths and young adults. Anthropometric and vertical jump ground reaction forces were collected from 460 male volunteers (age: 12–24 years). Of these 460 volunteers, a stratified random sample of 45 subjects representing 3 different age groups (12–15 years [n = 15], 16–18 years [n = 15], and 19–24 years [n = 15]) was selected as a validation sample. Data from the remaining 415 subjects were used to develop a new equation (“Novel”) to estimate PP using age, body mass (BM), and vertical jump height (VJH) via backward stepwise regression. Independently, age (r = 0.57), BM (r = 0.83), and VJ (r = 0.65) were significantly (p < 0.05) correlated with PP. However, age did not significantly (p = 0.53) contribute to the final prediction equation (Novel): PP (watts) = 63.6 × VJH (centimeters) + 42.7 × BM (kilograms) − 1,846.5 (r = 0.96; standard error of the estimate= 250.7 W). For each age group, there were no differences between actual PP (overall group mean ± SD: 3,244 ± 991 W) and PP estimated using Novel (3,253 ± 1,037 W). Conversely, other previously published equations produced PP estimates that were significantly different than actual PP. The large sample size used in this study (n = 415) likely explains the greater accuracy of the reported Novel equation compared with previously developed equations (n = 17–161). Although this Novel equation can accurately estimate PP values for a group of subjects, between-subject comparisons estimating PP using Novel or any other previously published equations should be interpreted with caution because of large intersubject error (± >600 W) associated with predictions. [ABSTRACT FROM AUTHOR]

Background: The incidence of anterior cruciate ligament (ACL) injury can be decreased through the use of intervention programs. However, the success of these programs is dependent on access to a skilled trainer who provides feedback; as such, these programs would benefit from a simple device with the capacity to provide high-quality feedback.Hypothesis: Feedback based on kinematic measurements from a simple inertial sensor-based system can be used to modify key ACL injury risk metrics (knee flexion angle, trunk lean, knee abduction moment) during jump landing.Study Design: Controlled laboratory study.Methods: Seventeen subjects (7 male) were tested during drop jump tasks. Their movements were measured simultaneously with inertial, optoelectronic, and force platform systems. Feedback provided to the subjects was based only on measurements from the inertial sensor-based system (knee flexion angle, trunk lean, and thigh coronal velocity). The subjects conducted a baseline session (without landing instructions), then a training session (with immediate feedback), and finally an evaluation session (without feedback). The baseline and evaluation sessions were then tested for changes in the key risk metrics.Results: The subjects increased their knee flexion angle (16.2°) and trunk lean (17.4°) after the training. They also altered their thigh coronal angular velocity by 29.4 deg/s and reduced their knee abduction moment by 0.5 %BW·Ht. There was a significant correlation (R2 = 0.55) between the change in thigh coronal angular velocity and the change in knee abduction moment.Conclusion: Subjects reduced key risk metrics for ACL injury after training with the system, suggesting the potential benefit of instrumented feedback for interventional training.Clinical Relevance: Interventional training for reducing the risk of ACL injury could be improved with a simple device that provides immediate feedback. [ABSTRACT FROM PUBLISHER]

The article reports on research which was conducted to investigate the effect internal and external attentional focus strategies had on peak force and performance in the standing long jump. Researchers had all subjects perform five standing long jumps. They found that external focus strategies resulted in greater jump distance and that there were no differences in peak force seen between internal and external focus subjects.

The article reports on research which was conducted to compare the effects weightlifting and kettlebell training had on vertical jump, strength and body composition in 30 healthy men. Researchers found that while both exercise regimens increased strength and power, there was a larger increase in strength in those subjects who participated in weightlifting.

Context: Excessive knee valgus during dynamic tasks is thought to contribute to lower extremity overuse and traumatic injuries. Clinically, assessments of frontal-plane knee motion typically include measures of the distance between the knees during landing. However, it is not clear how this clinical assessment relates to knee-abduction angle or how it is influenced by the position of the lower extremities in the transverse and frontal planes. Objective: To determine whether normalized knee separation distance (NKSD) is a predictor of knee-abduction angles and to assess the influence of lower extremity transverse-plane and frontal-plane angles on NKSD during a drop land. Design: Cross-sectional study. Setting: Motion analysis laboratory. Patients or Other Participants: Twenty-five healthy female athletes. Intervention(s): The frontal-plane distance between the 2-dimensional coordinates of markers over the greater trochanters (intertrochanteric distance), lateral femoral epicondyles (knee separation distance), and lateral malleoli (stance width) bilaterally was calculated during a drop land. The knee separation distance was normalized by intertrochanteric distance (NKSD). Concurrently, 3-dimensional lower extremity transverse-plane and frontal-plane kinematics were obtained. Main Outcome Measure(s): We assessed NKSD, stance width, and bilateral average knee and hip transverse plane and frontal-plane angles and ankle frontal-plane angles. Linear regression was used to determine the association between NKSD and bilateral average knee frontal-plane angles. Step- wise multiple regression was used to identify the best predictors of NKSD during the drop land. Results: After we controlled for stance width, NKSD explained 52% of the variance in the knee frontal-plane angle. When we took lower extremity kinematics into account, after controlling for stance width, the average hip frontal-plane angle was the best predictor of NKSD, explaining 97% of the variance. Conclusions: Although NKSD is a predictor of knee- abduction angle, frontal-plane hip angle and stance width are strongly related to NKSD. Caution must be taken when interpreting NKSD as knee abduction. [ABSTRACT FROM AUTHOR]