Abdominal crunch

RT consisted of five machine-supported exercises to target all major muscle groups (abdominals, lower back, upper back, chest, and legs) using the following exercise devices: Chest press, lat pulldown machine, lower back machine, abdominal crunch, and leg press (TechnoGym, Neu-Isenburg, Germany). Based on the 1RM tests performed every 4 weeks, the weight load was progressively increased over the 12 weeks to achieve the following target ranges: week 1–4: 50–60% 1RM; week 5–8: 60–75% 1RM; week 9–12: 70–80% 1RM. Repetitions were performed with 2 s of concentric (weight lifting phase) and 2 s of eccentric (weight lowering phase) muscle work until failure. The 1-RT group performed one set of each exercise with a resting period of 2 min between exercises. The 3-RT consisted of three sets of each exercise with similar resting periods between sets and exercises as 1-RT. As the number of repetitions decreased with increasing intensity, the mean session time decreased during the training period from ~20 min/session to ~11 min/session in the 1-RT group and from ~60 min/session to ~38 min/session in the 3-RT group, respectively.

All 1-RT sessions started with a short warm-up of low-intensity ergometer cycling for 5 min. The main part of the session involved five resistance exercises to address the major muscle groups (abdominals, lower back, legs, chest, and upper back) with the following exercise machines: abdominal crunch, lower back machine, leg press, chest press, and latissimus pulldown machine (TechnoGym, Neu-Isenburg, Germany). For each exercise, a single set of exercise was performed until volitional failure. Each repetition was performed with a 2 s concentric and 2 s eccentric phase of muscle work. The weight load for each exercise was determined based on a maximum strength testing (one-repetition maximum, 1RM) that was performed at T-1 and every 4 weeks of the intervention period, as previously described in detail [41 (link)]. As recommended for previously untrained individuals, a moderate weight load of 50–60% of 1RM was initially used for each exercise to accustom patients to RT [63 (link)]. According to RT guidelines and recent recommendations [63 (link),64 (link),65 (link)], the weight load was progressively increased in 4-week cycles using the following pattern: 50–60% 1RM during weeks 1–4; 60–75% 1RM during weeks 5–8; and 70–80% 1RM during weeks 9–12. The average total time effort per session was ~15 min (excluding warm-up).

Each RT session started with a 5 min warm-up of low intensity ergometer cycling. Subsequently, five exercises were performed to address all main muscle groups (i.e., chest, upper back, abdominals, lower back, and legs) using the following weight-machines: Chest press, lat pulldown machine, lower back machine, abdominal crunch, and leg press (TechnoGym, Neu-Isenburg, Germany). Based on the Fmax values determined baseline and thereafter every 4 weeks, the weight load was progressively elevated over the 12 weeks as follows: 50–60% Fmax during week 1–4; 60–75% Fmax during week 5–8; and 70–80% Fmax during week 9–12. All exercises were performed according to the following pattern: 2 s of concentric (weightlifting phase) and 2 s of eccentric (weight lowering phase) muscle work until fatigue. The 1-RT group performed a single set of each exercise. Total time per exercise session was ~15 min (including the 2 min resting phases between exercises). The 3-RT group performed three sets of each exercise with 2 min rest in between, adding up to a total session time of ~50 min.