Relationship Between Knee Frontal Plane Projection Angle and Lower Limb Muscle Activity in Female Athletes.

CONTEXT: Anterior cruciate ligament injuries are directly related to the control of dynamic knee valgus in the landing of a jump, and this is mainly due to the correct activation and neuromuscular function of the lower-extremity muscles. The aim of the study is to assess the relationship between lower limb muscle activity during a single-legged drop jump and knee frontal plane projection angle (FPPA). DESIGN: A correlation study. METHODS: Thirty healthy collegiate female athletes were included in the study. Main outcomes measures were peak knee FPPA and muscle activity (% of maximal voluntary isometric contraction). Peak knee FPPA during a single-legged drop jump test was identified using a 2-dimensional motion analysis system. Muscle activity was assessed using a surface electromyograph for gluteus maximus, gluteus medius, biceps femoris, semitendinosus, vastus medialis quadriceps, vastus lateralis quadriceps, medial gastrocnemius, and lateral gastrocnemius. All variables were assessed for both dominant and nondominant limbs. A correlation analysis between peak knee FPPA and muscle activity was performed. Statistical significance was set at P <.05. RESULTS: A mean peak knee FPPA of 14.52° and 13.38° was identified for dominant and nondominant limb single-legged drop jump test, respectively. Muscle activity (% of maximal voluntary isometric contraction) for muscles assessed ranged from 43.97% to 195.71% during the single-legged drop jump test. The correlation analysis found no significant correlation between any of the muscles assessed and peak knee FPPA during the single-legged drop jump test (Pearson coefficient between -.3 and .1). CONCLUSIONS: There is no association between muscle activity from the lower limb muscles and the knee FPPA during a single-legged drop jump in female athletes. Thus, different muscle properties should be assessed in order to understand such an important movement as the knee FPPA during a jump.

Effects of Adding an Online Exercise Program on Physical Function in Individuals Hospitalized by COVID-19: A Randomized Controlled Trial.

The worldwide pandemic caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus has impacted all healthcare systems. One potential sequela experienced by hospitalized coronavirus disease 2019 (COVID-19) survivors includes muscle weakness with a reduction in strength and, consequently, a possible increase in frailty. The aim of this clinical trial was to evaluate the efficacy of adding an online therapeutic exercise program for 8 weeks to the medical prescriptions on functional variables in patients hospitalized due to COVID-19. A randomized controlled trial including 70 previously hospitalized COVID-19 survivors was conducted. Patients were randomly allocated to an experimental (n = 35) or control (n = 35) group. Both groups received regular prescriptions provided by their medical doctors. The experimental group also received a live online therapeutic exercise program for 8 weeks (3 sessions/week). Handgrip strength, gait speed, lower-extremity strength, balance, and frailty were assessed at baseline, at the end of the program, and one month after the end of the intervention. The repeated measures analysis of variance revealed significant Group*Time interactions for all the outcomes: (handgrip dominant: F = 17.395, p < 0.001, η2 = 0.24; handgrip non-dominant: F = 33.197, p < 0.001, η2 = 0.33; 4 m walk test (4WT): F = 13.039, p = 0.001, η2 = 0.16; short physical performance battery (SPPB): F = 26.421, p < 0.001, η2 = 0.28; the five chair-raise test (5CRT): F = 5.628, p = 0.004, η2 = 0.08; FRAIL scale: F = 11.249, p = 0.001, η2 = 0.14): patients in the experimental group experienced greater improvements in all outcomes than those assigned to the control group. This study revealed that the addition of an online exercise program for 8 weeks obtained greater improvements in handgrip strength, gait speed, lower-extremity strength, balance, and frailty in a sample of previously hospitalized COVID-19 survivors than application of just usual medical prescription.

Relationship between lower limb EMG activity and knee frontal plane projection angle during a single-legged drop jump.

OBJECTIVES: To assess a relationship between lower limb muscle activity and the frontal plane knee kinematics during a single-legged drop jump. DESIGN: Correlation study; SETTING: Functional Anatomy Laboratory. PARTICIPANTS: 35 healthy collegiate male athletes. MAIN OUTCOME MEASURES: Muscle activity (%MVIC) of gluteus maximus, gluteus medius, biceps femoris, semitendinosus, vastus medialis quadriceps, vastus lateralis quadriceps, medial gastrocnemius and lateral gastrocnemius; peak knee frontal plane projection angle; and Pearson's correlation coefficients between muscle activity and peak knee frontal plane projection angle. All outcomes were assessed for both dominant and non-dominant limbs. RESULTS: Significant correlations (r = 0.46-0.60, P < 0.05) were found between the muscle activities of the gluteus maximus, gluteus medius, biceps femoris, and semitendinosus, when compared to the knee frontal plane projection angle. CONCLUSION: Gluteal muscles and hamstring muscles are associated with the peak knee frontal plane projection angle during a single-legged drop jump test. Thus, gluteal and hamstring muscle activities should be considered when developing rehabilitation or injury prevention programs.

Biceps Femoris Activation during Hamstring Strength Exercises: A Systematic Review.

BACKGROUND: The aim of the study was to systematically evaluate the biceps femoris long head activation across cross-sectional hamstring strength exercise studies. METHODS: A systematic review design was followed. The search strategy conducted in PubMed, Cochrane Library, and Web of Sciences databases found a total of 3643 studies. Once inclusion and exclusion criteria were applied, 29 studies were finally included in this systematic review. A total of 507 participants and 114 different exercises were analyzed. Exercises were evaluated individually and grouped into several categories: Nordics, isokinetic exercises, lunges, squats, deadlifts, good mornings, hip thrusts, bridges, leg curls, swings, hip and back extensions, and others. RESULTS: Results showed the isokinetic and Nordic exercises as the categories with highest biceps femoris activation (>60% of Maximal Voluntary Isometric Contraction). Nordic hamstring exercise ankle dorsiflexion was the exercise that achieved the highest biceps femoris long head activation (128.1% of its Maximal Voluntary Isometric Contraction). CONCLUSIONS: The results from this systematic review suggest that isokinetic and Nordic exercises seem to be the best option to activate biceps femoris long head. Future studies evaluating the implementation of these exercises in prevention programs are needed.