MULTI-MODAL EXERCISE SYSTEM: TEN-MUSCLE sEMG AND SEX DIFFERENCES ACROSS THREE ANGLES

INTRODUCTION: Across muscles, surface EMG (sEMG) generally increases with steeper angles, indicating greater muscle activation. Changes in body or joint angles alter load distribution and muscle engagement, enhancing strength, stability and functional performance. Additionally, research has demonstrated sex-related differences attributed to variations in muscle mass distribution and strength levels between males and females. To compare sEMG amplitude across ten muscles during standardized exercise on the Challenger at three device angles: Power Sled (horizontal; Angle 1), Power Stairs (forward-incline; Angle 5), and Power Climb (vertical; Angle 9). METHODS: Twenty-three healthy young adults (13 women, 10 men; 23.7 ± 6.1 y) of a planned N = 40 completed a single 60-min visit. Participants performed standardized, simultaneous upper- and lower-limb dynamic movements on the Challenger at three device angles—Power Sled (horizontal; Angle 1), Power Stairs (forward-incline; Angle 5), and Power Climb (vertical; Angle 9). The same movement pattern was used at each angle. sEMG was recorded from ten muscles—biceps brachii, triceps brachii, pectoralis major, upper trapezius, latissimus dorsi, rectus abdominis, gluteus maximus, quadriceps, hamstrings, and gastrocnemius—during each angle condition. Device resistance was fixed at level 5 (scale: 1 = easiest, 10 = hardest). Global ratings of perceived exertion (Borg 6–20) were obtained after each angle condition. RESULTS: A mixed repeated-measures ANOVA will be administered to analyze muscle activation of each of the ten muscle groups (biceps brachii, triceps brachii, quadriceps, hamstrings, pectoralis major, upper trapezius, gluteus maximus, gastrocnemius, rectus abdominis, and latissimus dorsi) across Angle (angle1, angle 5, angle 9) x Sex women, men). Assumptions will be checked; sphericity will be tested, and corrections applied as needed. Post hoc comparisons with Bonferroni adjustment will be administered if significant. The critical alpha level will be set at p