Efectos de diferentes protocolos de fortalecimiento de miembro inferior sobre la fuerza, potencia y actividad muscular en sujetos sedentarios y físicamente inactivos: una revisión sistemática

The purpose of this systematic review was: a) to determine the quality of evidence from studies assessing the effects of different lower limb strengthening protocols on muscle activity, strength, and power in sedentary and/or physically inactive subjects; and b) to determine the effectiveness of lower extremity strengthening protocols on muscle activity, strength, and power in sedentary and/or physically inactive subjects. Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) statements were followed using keywords associated with strength training, lower limb, sedentary, and physical inactivity. Four databases were used: Medline via PubMed, Web of Science, Scopus and SPORTDiscus. Methodological quality was assessed using the PEDro scale. A total of 164 articles were retrieved, six included in this review. Four studies were classified as fair methodological quality, and two were considered of good methodological quality. Due to the heterogeneity in methodological aspects and the limited number of articles including the variables under study, it was not possible to establish a measure of effectiveness of lower limb strengthening protocols on muscle activity, strength, or power. In conclusion, strength training in the lower limb seems to improve the levels of strength, power, and muscular activity in sedentary subjects. However, due to the limited number of articles, methodological variability, and training methods used, it is necessary to conduct new studies that control these variables.El propósito de esta revisión sistemática fue: a) determinar la calidad de la evidencia de los estudios que evaluaron los efectos de diferentes protocolos de fortalecimiento de miembros inferiores sobre la actividad, la fuerza y la potencia muscular en sujetos sedentarios y/o físicamente inactivos; y b) determinar la efectividad de los protocolos de fortalecimiento sobre la actividad, fuerza y potencia muscular de miembros inferiores en sujetos sedentarios y/o físicamente inactivos. Se siguieron los criterios PRISMA (Preferred Reporting Items for Systematic Review and Meta-Analyse) utilizando palabras clave asociadas con el entrenamiento de fuerza, extremidades inferiores, sedentarismo e inactividad física. Se revisaron cuatro bases de datos: Medline vía PubMed, Web of Science, Scopus y SPORTDiscus. La calidad metodológica se evaluó mediante la escala PEDro. Se recuperaron 164 artículos en total, seis incluidos en esta revisión. Cuatro estudios se clasificaron como de calidad metodológica regular y dos se consideraron de buena calidad metodológica. Debido a la heterogeneidad en los aspectos metodológicos y al escaso número de artículos que incluyeron las variables en estudio, no fue posible establecer una medida de efectividad de los protocolos de fortalecimiento de miembros inferiores sobre la actividad, la fuerza o la potencia muscular. En conclusión, el entrenamiento de fuerza en el miembro inferior parece mejorar los niveles de fuerza, potencia y actividad muscular en sujetos sedentarios. No obstante, debido al número limitado de artículos, la variabilidad metodológica y los métodos de entrenamiento utilizados, es necesario realizar nuevos estudios que controlen estas variables

Isokinetic force-power profile of the shoulder joint in males participating in CrossFit training and competing at different levels

Background As participants who engage in CrossFit training and competition perform a large volume of high intensity overhead activities, injuries to the shoulder are one of the most common in this sport. Previous research in other sports has indicated that the isokinetic force power profile of the shoulder joint (IPSJ) rotator muscles may assist in the prediction of shoulder injury. Aim Therefore, the objective of this study was to determine the IPSJ in males engaged in CrossFit training at different competitive levels. Methods In a cross-sectional study design, participants (age, 24.1 ± 2.7 years) classified as ‘beginner’ (n = 6), ‘intermediate’ (n = 7) or ‘advanced’ (n = 9) provided informed consent to participate in this study. The IPSJ assessment involved rotational and diagonal movements, including internal and external shoulder rotator muscles, at both 180°.s‾¹ and 300°.s‾¹. The variables analysed were peak torque/body mass (%), mean power (W) and the external/internal peak torque/body mass ratio (%). A Kruskal–Wallis test was used to compare the IPSJ of the three groups, with Dunn’s test used for post-hoc analysis. The alpha level was set at p < 0.05. Results The IPSJ showed greater torque and power values in those who competed at the advanced level as compared to those at a lower competitive level (i.e. intermediate, beginner). This was observed mainly for the internal rotation and internal diagonal movements at both 180°.s‾¹ and 300°.s‾¹. However, such differences between competitive levels were, in general, absent for the external rotation and external diagonal movements. Moreover, the participants from the advanced competitive level exhibited an imbalance of peak torque between the muscles responsible for the external–internal rotational and external-internal diagonal movements of the shoulder (i.e. peak torque external/internal ratio <66%), particularly in the dominant shoulder. Conclusion These findings suggest greater development of the shoulder internal rotators and a higher probability of shoulder injury in CrossFit athletes at the advanced competitive level. Based on these results, participants engaged in CrossFit training and competition may wish to increase the volume of training for the shoulder external rotator muscles to complement the large increases in shoulder internal rotator strength that occur as a part of their regular training regimes

Effects of Traditional Strength Training Versus Jump Training on Muscular Fitness among Physically Inactive and Sedentary Young Adults

Background: The effects of Traditional Resistance Training (TRT) and Plyometric Jump Training (PJT) had never been compared in participants that are both sedentary and physically inactive. Results derived from such research may allow important practical applications. Objective: The aim of this study was to compare the effects of 4-weeks of TRT versus PJT programs on the muscular fitness of sedentary and physically inactive participants. Methods: Baseline and follow-up tests included the assessment of Squat Jump (SJ), Countermovement Jump (CMJ), elastic index, and maximal strength of the knee extensors (MVS). Males and females (age range, 18-29 years) were randomly assorted into a control group (CG, n=11), TRT (n=8), and PJT groups (n=9). The TRT program emphasized slow-speed movements with free weights. The PJT program emphasized high-speed jump movements without external loads. Both TRT and PJT sessions lasted 30-minutes. Dependent variables were analyzed in separate three (Groups) × two (Time: pre, post) ANOVA, with Bonferroni-adjusted α (p<0.05). Results: Main effects of time (all p<0.05) were observed for SJ (ηp2 = 0.51), CMJ (ηp2 = 0.33), and MVS (ηp2 = 0.33). Post-hoc analyses revealed similar significant (all p<0.05) improvements in the TRT and PJT groups for SJ (∆, 95%CL, 9.0-22.5%), CMJ (∆, 95%CL, 11.7-24.4%), and MVS (∆, 95%CL, 5.8-21.3%). No significant changes were observed in the control group. No changes were observed for the elastic index. Conclusion: In otherwise healthy participants that are both physically inactive and sedentary, both TRT and PJT protocols are equally effective in improving the muscular fitness

Age-dependent Knee Joint Isokinetic Profile in Professional Male Soccer Players

Background: The knee-joint isokinetic profile (KJIP) injury risk factor may be modulated by chronological age, however, comparative data for elite male soccer players aged 25 years and older is lacking. Objective: To describe and compare the knee-joint isokinetic profile (KJIP) according to the chronological age of professional male soccer players. Method: In a cross-sectional study design, sixty-three soccer athletes from the first Chilean soccer division (A-series) were divided into younger and older groups (age ≤ 25 years; n = 35 and age 25 years; n = 28, respectively). In both groups the IPKJ was assessed at 60°.s-1 in concentric mode. Results: The older group had lower extensor peak torque (p .05). The younger group showed correlations between flexors peak torque and extensors mean power (p .001). In the older group, flexors peak torque and flexors mean power were correlated. The flexors peak torque, total work, and mean power symmetric index (SI) exhibited values 10 % for both groups. The extensors SI showed values 10 % for mean power, although only in the older group. Conclusion: Several differences in the KJIP were noted between professional male soccer players aged ≤ 25 years and 25 years. Current results offer injury prevention insights, discussed in the current manuscript