Targeted muscle activation in Bulgarian split squat variations: effects of trunk position and suspension-based execution

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PURPOSE: Optimizing muscle activation through exercise variation is critical for enhancing performance and reducing injury risk. This cross-sectional study examined how trunk position (neutral vs. flexion) and surface stability (ground-based vs. suspension-based) influence lower extremity and trunk muscle activation during the Bulgarian Split Squat (BSS). METHODS: Twenty-one trained female athletes (mean ± SD: age 20.3 ± 2.5 years; height 165.9 ± 5.8 cm; body weight 58.5 ± 5.7 kg) participated in the study. Surface electromyography was used to assess activation of eight lower extremity and trunk muscles: gluteus medius (GMed), gluteus maximus (GMax), vastus lateralis (VL), rectus femoris (RF), vastus medialis (VM), semitendinosus (ST), biceps femoris (BF), and erector spinae (ES) during four BSS variations. RESULTS: Suspension-based BSS resulted in significantly greater activation of the ES (p = 0.046), while trunk flexion increased activation in the GMax, BF, and RF muscles (p < 0.05). CONCLUSION: Suspension-based BSS is particularly effective for targeting trunk stabilizers like the ES, while trunk flexion enhances posterior chain muscle activation, especially GMax and BF. These variations can be strategically applied in strength training and rehabilitation to meet specific neuromuscular goals. In practice, the findings may guide individualized programming for enhancing performance or preventing injuries in female athletes. TRIAL REGISTRATION: ClinicalTrials.gov identifier NCT06112015, registered on 01/11/2023.