The effect of exercise complexity on trunk muscle activation and perceived exertion during body-weight training in recreationally trained adults

Introduction The aim of the present study was to investigate the acute effects of varying exercise complexity on trunk muscle activity in recreationally trained adults during seven trunk-specific body-weight (BW) exercises. Methods Twenty-eight participants were recruited (15 women and 13 men, age: 32 ± 9 years, height: 173 ± 9 cm, body mass: 73 ± 10 kg, training experience: 15 ± 9 years). Participants performed seven trunk-specific BW exercises in a randomized, counter-balanced order. Each exercise was performed isometrically (15 s) at 3–4 complexity levels, induced by changing the base of support, altering lever arms (using body tilt or body position), and applying bilateral versus unilateral execution. Electromyographic activity was collected from the rectus abdominis, external oblique, and spinal erector muscles. After completing each complexity level, participants rated their perceived exertion (RPE). Results Muscle activation was significantly higher at larger complexity levels ( p < 0.05, η p 2 = 0.12–0.89), and this effect was most pronounced in the primary target muscles for each exercise. Higher levels of muscle activation were accompanied by higher levels of perceived exertion ( p < 0.05, w = 0.19–0.90). Discussion In conclusion, increasing instability, applying unilateral performance, and/or changing body position led to increased activation of trunk muscles and RPE during BW exercises in recreationally trained adults, with the highest activation observed in primary target muscles for each specific exercise.