Ribeiro-Alvares, JB, Marques, VB, Vaz, MA, and Baroni, BM. Four weeks of Nordic hamstring exercise reduce muscle injury risk factors in young adults. J Strength Cond Res 32(5): 1254-1262, 2018-The Nordic hamstring exercise (NHE) is a field-based exercise designed for knee-flexor eccentric strengthening, aimed at prevention of muscle strains. However, possible effects of NHE programs on other hamstring injury risk factors remain unclear. The purpose of this study was to investigate the effects of a NHE training program on multiple hamstring injury risk factors. Twenty physically active young adults were allocated into 2 equal-sized groups: control group (CG) and training group (TG). The TG was engaged in a 4-week NHE program, twice a week, 3 sets of 6-10 repetitions; while CG received no exercise intervention. The knee flexor and extensor strength were assessed through isokinetic dynamometry, the biceps femoris long head muscle architecture through ultrasound images, and the hamstring flexibility through sit-and-reach test. The results showed that CG subjects had no significant change in any outcome. TG presented higher percent changes than CG for hamstring isometric peak torque (9%; effect size [ES] = 0.27), eccentric peak torque (13%; ES = 0.60), eccentric work (18%; ES = 0.86), and functional hamstring-to-quadriceps torque ratio (13%; ES = 0.80). The NHE program led also to increased fascicle length (22%; ES = 2.77) and reduced pennation angle (-17%; ES = 1.27) in biceps femoris long head of the TG, without significant changes on muscle thickness. In conclusion, a short-term NHE training program (4 weeks; 8 training sessions) counteracts multiple hamstring injury risk factors in physically active young adults.
Context: Hamstring strain injury (HSI) is the most prevalent injury in football (soccer), and a few intrinsic factors have been associated with higher injury rates. Objective: To describe the prevalence of the main intrinsic risk factors for HSI in professional and under-20 football players. Design: Cross-sectional study. Setting: Physiotherapy laboratory, Federal University of Health Sciences of Porto Alegre (Brazil). Participants: A total of 101 football players (52 professional and 49 under-20 players). Intervention: An evidence-based testing protocol for screening HSI risk factors. Main Outcome Measures: Anamnesis, ultrasonography of the hamstrings, passive straight-leg raise test, Functional Movement Screen, and isokinetic dynamometry were performed. Eleven HSI risk factors for each leg were assessed, besides the player’s age as a systemic risk factor. Reports were delivered to the coaching staff. Results: Professionals had greater prevalence of HSI history compared with under-20 players (40% vs 18%). No between-group differences were found for the other screening tests. Altogether, 30% of players had already sustained at least one HSI; 58% had a history of injuries in adjacent regions; 49% had short biceps femoris fascicles; 66% and 21% had poor passive and active flexibility, respectively; 42% and 29% had deficits in functional movements and core stability, respectively; 7% and 26% presented bilateral imbalance for hamstring concentric and eccentric strength, respectively; 87% and 94% obtained low values for hamstring-to-quadriceps conventional and functional ratios, respectively. Two-thirds of players had 3 to 5 risk factors per leg. None of the players was fully free of HSI risk factors. Conclusion: Most football players present multiple risk factors for sustaining an HSI. Hamstring weakness is the most prevalent risk factor, but the teams should also be aware of deficits in flexibility, core stability, functional movements, and hamstring fascicle length.
Promising effects of phototherapy on markers of exercise-induced muscle damage has been already demonstrated in constant load or isokinetic protocols. However, its effects on more functional situations, such as plyometric exercises, and when is the best moment to apply this treatment (pre- or post-exercise) remain unclear. Therefore, the purpose of this study was to investigate the effect of low-level laser therapy (LLLT) before or after plyometric exercise on quadriceps muscle damage markers. A randomized, double-blinded, placebo-controlled trial was conducted with 24 healthy men, 12 at pre-exercise treatment group and 12 at post-exercise treatment group. Placebo and LLLT (810 nm, 200 mW per diode, 6 J per diode, 240 J per leg) were randomly applied on right/left knee extensor muscles of each volunteer before/after a plyometric exercise protocol. Muscular echo intensity (ultrasonography images), soreness (visual analogue scale - VAS), and strength impairment (maximal voluntary contraction - MVC) were assessed at baseline, 24, 48, and 72 h post-exercise. Legs treated with LLLT before or after exercise presented significantly smaller increments of echo intensity (values up to 1 %) compared to placebo treatments (increased up to ∼7 %). No significant treatment effect was found for VAS and MVC, although a trend toward better results on LLLT legs have been found for VAS (mean values up to 30 % lesser than placebo leg). In conclusion, LLLT applied before or after plyometric exercise reduces the muscle echo intensity response and possibly attenuates the muscle soreness. However, these positive results were not observed on strength impairment.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.