ECSS Paris 2023: CP-MH04
INTRODUCTION: The gluteus medius (GMed) plays a critical role in pelvic stability and frontal-plane control during functional movements. Weakness or delayed activation of the GMed is often associated with compensatory overactivation of the tensor fasciae latae (TFL), which may contribute to altered lower-extremity alignment and increased injury risk. Although many rehabilitation studies have focused on maximizing GMed activation, evaluating absolute muscle activity alone may not adequately explain inter-muscular coordination or compensatory strategies. Furthermore, neuromuscular activation patterns may differ between males and females due to anatomical and neuromuscular factors. Therefore, this study aimed to examine sex-related differences in EMG activation patterns of the GMed and TFL during commonly prescribed rehabilitation exercises for GMed strengthening. METHODS: Twenty-six healthy adults (13 males and 13 females) participated in this cross-sectional study. Surface electromyographic (EMG) signals were recorded from the GMed and TFL using a wireless EMG system during the performance of ten lower-extremity rehabilitation exercises commonly used to strengthen the GMed. Electrode placement followed SENIAM recommendations. All EMG signals were normalized to maximum voluntary isometric contraction (MVIC) values. Mean normalized EMG amplitudes (%MVIC) were calculated, and the relative activation ratio between the two muscles (GMed/TFL) was computed to assess selective muscle activation. A two-way mixed repeated-measures ANOVA (sex × exercise) was used for statistical analysis. RESULTS: FL activation was significantly higher in females than in males during the clam shell, side-lying hip abduction, knee side plank with hip abduction (supporting and elevated leg), and lateral band walk exercises (p < .05). GMed activation was significantly greater in females during the side-lying hip abduction, knee side plank with hip abduction (supporting and elevated leg), lateral band walk, pelvic drop, and single-leg squat exercises (p < .05). No significant sex differences were observed in the GMed/TFL ratio across most exercises. However, males demonstrated a significantly higher GMed/TFL ratio during the clam shell exercise (p < .05), whereas females exhibited a significantly higher ratio during the side plank with hip abduction (supporting and elevated leg) (p < .05). CONCLUSION: Females may require greater neuromuscular activation to meet the same relative task demands, aligning with prior reports of sex differences in motor unit recruitment and firing strategies. Notably, even when absolute gluteus medius (GMed) activation was comparable between sexes, the GMed/tensor fasciae latae (TFL) ratio differed in selected exercises, indicating sex-specific coordination patterns that are not captured by absolute EMG alone. Overall, these findings suggest that both activation magnitude and inter-muscular coordination should be considered when selecting and evaluating GMed-strengthening exercises.
Read CV Youngbae EumECSS Paris 2023: CP-MH04
INTRODUCTION: Pregnancy and postpartum substantially affect athletes’ careers. In general, 22.3–59.0% experience low back pain and/or pelvic girdle pain likely due to altered spinal alignment and reduced function of abdominal muscle and pelvic floor muscle (PFM). While athletes report similar pain prevalence [1], longitudinal changes in their spinal alignment and PFM function remain scarcely investigated, despite their importance for safe return to sport. Therefore, this study exploratively investigated these parameters in elite athletes. METHODS: Eight elite athletes (age:30.8 ± 4.5years) participated. Seven athletes had vaginal deliveries, and one had a cesarean section; seven were primiparous and one was multiparous. Measurements were conducted at mid-pregnancy (Mid; 20–22 weeks), late pregnancy (Late; 30–32 weeks), and 1 and 3 months postpartum (1M and 3M). Spinal alignment was assessed using whole-body three-dimensional photonic scanning (Body Line Scanner C9036, Japan). Markers were placed on the spinous processes of C7, T12, and S2, and data were collected in a neutral standing posture. A C7–S2 spinal line was constructed from polygon data, and thoracic kyphosis and lumbar lordosis angles were calculated as central angles based on the Flexicurve method [2]. PFM endurance was assessed by digital palpation performed by a physical therapist and classified as possible or impossible to sustain a 10-s voluntary contraction [3]. Repeated-measures one-way ANOVA with Bonferroni post-hoc tests were used for spinal angles, with the significance level set at p < 0.05. Partial eta-squared (η²ₚ) was used to assess the magnitude of significant differences (η²ₚ ≤ 0.01 small, ≤ 0.06 medium, ≥ 0.14 large), and Cohen’s d was calculated as an effect size (d ≤ 0.2 small, ≤ 0.5 medium, ≥ 0.8 large). The proportion of participants able to sustain a 10-s PFM contraction was determined for each phase. RESULTS: No significant phase effect was found for lumbar lordosis (p > 0.05, η²p = 0.16) or thoracic kyphosis (p > 0.05, η²p = 0.06), and no significant post-hoc differences were found. A moderate effect size (d = 0.87) was observed for lumbar lordosis from Late (47.0 ± 10.4°) to 1M (55.8 ± 10.7°), whereas thoracic kyphosis showed only small effect sizes (d = 0.06-0.41). PFM endurance sustainment rates were 37.5% (Mid), 75.0% (Late), 37.5% (1M), and 62.5% (3M). CONCLUSION: Although no statistically significant phase effects were detected, moderate changes in lumbar lordosis were observed from Late to 1M, whereas PFM endurance appeared to be temporarily reduced at 1M before recovering. These findings may help guide decisions regarding training intensity during the early postpartum period. References 1. Bø et al., Scand J Med Sci Sports, 2007. 2. Grindle et al., JOR Spine, 2020. 3. Starzec-Proserpio et al., Int. J. Environ. Res. Public Health, 2022.
Read CV Yuriko NishikawaECSS Paris 2023: CP-MH04
INTRODUCTION: Limb immobilisation induces rapid neuromuscular decline, with early strength losses primarily driven by neural mechanisms. Cross-education, whereby unilateral resistance training yields strength enhancements in the opposite non-exercised limb, has been proposed as a countermeasure to immobilisation-induced decline. The objective of this review was to quantify cross-education effects on muscle strength and size during unilateral limb immobilisation and examine the influence of muscle group specificity and immobilisation model. METHODS: A systematic review and three-level hierarchical random-effects meta-analysis were conducted following PRISMA 2020 guidelines. Eight studies (189 healthy adults) involving unilateral upper-limb immobilisation with contralateral resistance training were included. Standardised mean change raw scores with Hedges' g correction were calculated. Subgroup analyses examined trained homologous muscles and proximal versus distal immobilisation models. RESULTS: Cross-education significantly attenuated strength loss compared with immobilisation alone (g = 0.53, 95% CI [0.34–0.73], p < 0.001), with a smaller effect on muscle size (g = 0.19, 95% CI [0.05–0.33], p = 0.01). Strength preservation demonstrated protocol specificity (eccentric: g = 0.57, p = 0.012; combined concentric-eccentric: g = 0.685, p = 0.01), muscle specificity (trained homologous: g = 0.66 vs. overall: g = 0.53), and anatomical specificity (proximal: g = 0.62 vs. overall: g = 0.53). Size preservation was significant for proximal (g = 0.40, p = 0.01) but not distal immobilisation (g = 0.06, p = 0.48), with no protocol or muscle specificity. Strong correlations existed between trained and immobilised limb adaptations for strength (r = 0.79) and size (r = 0.81). CONCLUSION: Cross-education effectively preserves neuromuscular strength during immobilisation, with effects predominantly neural rather than structural, evidenced by robust, multi-dimensionally specific strength preservation but smaller, less specific size effects. Clinical implementation should prioritise eccentric or combined training protocols, particularly for proximal immobilisation, with realistic expectations that strength preservation is the primary benefit while size preservation is limited to proximal regions.
Read CV Justin AndrushkoECSS Paris 2023: CP-MH04