Leg press

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.

The study investigated whether mechano-biological descriptors, i.e. the temporal distribution of contraction modes, number of repetitions and total time-under-tension (TUT) could be extracted from accelerometer derived real-world dynamic resistance exercise data on different resistance exercise machines. Nine resistance exercise machines were selected at the gym located at ETH Zurich. The selected machines comprised the most often chosen exercises in a whole-body workout and were as follows: Adductor, Abductor, Chest Press, Leg Curl, Leg Extension, Leg Press, Lower Back, Total Abdominal and Vertical Traction (Technogym, Cesana, Italy). Video recordings, which are considered the gold standard, were made for all exercises.

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).