Background: Plyometric training (PT) has been widely studied in sport science. However, there is no review that determines the impact of PT on the structural variables and mechanical properties of the lower limbs and physical performance. Objective: The aim of this systematic review and meta-analysis was to determine the effects of PT on lower body muscle architecture, tendon structure, stiffness and physical performance. Methods: Five electronic databases were analysed. The inclusion criteria were: (1) Availability in English; (2) Experimental studies that included a PT of at least eight sessions; and (3) Healthy adults subjects. Four meta-analyses were performed using Review Manager software: (1) muscle architecture; (2) tendon structure; (3) muscle and tendon stiffness; (4) physical performance. Results: From 1008 search records, 32 studies were eligible for meta-analysis. Muscle architecture meta-analysis found a moderate effect of PT on muscle thickness (Standard Mean Difference (SMD): 0.59; [95% Confidence Interval (CI) 0.47, 0.71]) and fascicle length (SMD: 0.51; [95% CI 0.26, 0.76]), and a small effect of PT on pennation angle (SMD: 0.29; [95% CI 0.02, 0.57]). The meta-analysis found a moderate effect of PT on tendon stiffness (SMD: 0.55; [95% CI 0.28, 0.82]). The lower body physical performance meta-analysis found a moderate effect of PT on jumping (SMD: 0.61; [95% CI 0.47, 0.74]) and strength (SMD: 0.57; [95% CI 0.42, 0.73]). Conclusion: PT increased the thickness, pennation angle and fascicle length of the evaluated muscles. In addition, plyometrics is an effective tool for increasing tendon stiffness and improving jump and strength performance of the lower body.

The continued practice of a sport linked to the unilateral predominance of the dominant side can provoke chronic asymmetric adaptations in the myotendinous structure and mechanical properties. Objectives: The main purpose was to determine whether asymmetry between the preferred and non-preferred lower limb is present in the lower limb tendon structure, muscle architecture and stiffness values of professional badminton players. Sixteen male professional badminton players (age = 24.1 ± 6.7 years; body height = 177.90 ± 7.53 cm) participated in this study. The muscle architecture of the vastus lateralis (VL), medial gastrocnemius (MG) and lateral gastrocnemius (LG) and the structure of patellar and Achilles tendons were measured in the dominant and non-dominant lower limb with ultrasonography. Stiffness was also measured at the same points with a hand-held MyotonPro. Significant differences between the dominant and non-dominant lower limb were determined using Student’s t test for related samples. Bilateral differences were observed for thickness, width and cross-sectional area (CSA) in both tendons showing higher values for the dominant side: patellar tendon CSA (2.02 ± 0.64 vs. 1.51 ± 0.42 cm²; p < 0.05) and Achilles tendon CSA (1.12 ± 0.18 vs. 0.92 ± 0.28 cm²; p < 0.05). No significant differences were observed in muscle architecture and myotonic variables between the dominant and non-dominant lower limb. The prolonged practice of badminton caused asymmetries in the CSA, width and thickness of the patellar and Achilles tendon between the dominant and non-dominant lower limbs. No bilateral differences were found in the muscle architecture of VL, MG and LG or in the stiffness of any muscle or tendon analyzed.

The objective of this study was to evaluate the reliability of four methods of assessing vastus lateralis (VL) stiffness, and to describe the influence of structural characteristics on them. The stiffness of the dominant lower-limb’s VL was evaluated in 53 healthy participants (28.4 ± 9.1 years) with shear wave elastography (SWE), strain elastography (SE), myotonometry and tensiomyography (TMG). The SWE, SE and myotonometry were performed at 50%, and TMG was assessed at 30%, of the length from the upper pole of the patella to the greater trochanter. The thickness of the VL, adipose tissue and superficial connective tissue was also measured with ultrasound. Three repeated measurements were acquired to assess reliability, using intraclass correlation coefficients (ICC). Pearson’s correlation coefficients were calculated to determine the relationships between methodologic assessments and between structural characteristics and stiffness assessments of the VL. Myotonometry (ICC = 0.93; 95%-CI = 0.89,0.96) and TMG (ICC = 0.89; 95%-CI = 0.82,0.94) showed excellent inter-day reliability whereas with SWE (ICC = 0.62; 95%-CI = 0.41,0.77) and SE (ICC = 0.71; 95%-CI = 0.57,0.81) reliability was moderate. Significant correlations were found between myotonometry and VL thickness (r = 0.361; p = 0.008), adipose tissue thickness (r = −0.459; p = 0.001) and superficial connective tissue thickness (r = 0.340; p = 0.013). Myotonometry and TMG showed the best reliability values, although myotonometry stiffness values were influenced by the structural variables of the supra-adjacent tissue.

Background: Rhythmic gymnastics performance is characterized by technical elements involving flexibility, aerobic capacity and strength. Increased core strength in rhythmic gymnastics could lead to improved sporting performance. Objective: The aim of this study was to analyze the effect of 12 weeks of core muscle training on core muscle performance in rhythmic gymnasts. Methods: A randomized controlled study involving 24 rhythmic gymnastics was conducted. Participants were randomly assigned to a control group (CG; n = 12; age 13.50 ± 3.17 years) or a training group (TG; n = 12; age 14.41 ± 2.35 years). Body composition, isometric strength of trunk, core endurance and core muscle electromyographic activity were measured (EMG) after 12 weeks of core training. Independent sample t-tests were carried out to compare baseline values between groups. A two-way repeated-measures analysis of variance (ANOVA) (time × group) was applied. Results: The TG improved body composition, trunk lean mass (mean differences MD = −0.31; p = 0.040), lean mass (MD = 0.43; p = 0.037) and bone mass (MD = −0.06; p < 0.001) after training. Core training increased isometric strength of trunk, flexion test (MD = −21.53; p = 0.019) and extension test (MD = 22.7; p = 0.049), as well as the prone bridge core endurance test (MD = −11.27; p = 0.040). The EMG values also increased in the TG in prone bridge for front trunk (MD = −58.58; p = 0.026). Conclusions: Core strength training leads to improvements in body composition, as well as improvements in trunk strength and increases in muscle electromyographic activity. These improvements could therefore improve performance during competitive rhythmic gymnastics exercises.

The aim of this study was to analyse the association of the use of the mobile phone with physical fitness (PF) and academic performance in secondary school students and its gender-related differences. A total of 501 high school students participated in the study (236 girls and 265 boys; 12–18 years). Use of the mobile phone and sample distributions were done with the Mobile-Related Experience Questionnaire (CERM): low use of mobile phone (LMP = 10–15 points), medium use of mobile phone (MMP = 16–23 points) and high use of mobile phone (HMP = 24–40 points). PF via Eurofit test battery and academic performance were recorded, and gender was used as a differentiating factor. The HMP group registered lower values than the LMP group for academic performance (Spanish: 4.78 ± 2.26 vs. 3.90 ± 1.96 points; p = 0.007, Mathematics: 4.91 ± 2.23 vs. 4.00 ± 1.84 points; p = 0.007) and PF (Abdominals: 6.83 ± 2.40 vs. 5.41 ± 2.46 points; p < 0.001, Broad jump: 6.24 ± 3.02 vs. 4.94 ± 2.28 points; p = 0.013). The boy students showed greater values than girl students for PF in the LMP (medicine-ball-throw: 6.34 ± 2.24 vs. 5.28 ± 1.86 points, p = 0.007) and MMP (medicine-ball-throw: 6.49 ± 2.52 vs. 5.02 ± 1.68 points; p < 0.001) groups, but no gender-related differences were found in the HMP group. In conclusion, high use of the mobile phone was related to worse results in the PF tests and academic performance. Gender-related differences were found for academic performance regardless of the use of the mobile, but for physical fitness no gender differences were found in HMP group.