Unilateral high-load resistance training influences strength changes in the contralateral arm undergoing low-load training

• Published in: Journal of Science and Medicine in Sport Vol. 26; no. 8; pp. 440 - 445
• Main Authors: Bell, Zachary W., Wong, Vickie, Spitz, Robert W., Yamada, Yujiro, Song, Jun Seob, Kataoka, Ryo, Chatakondi, Raksha N., Abe, Takashi, Loenneke, Jeremy P.
• Format: Journal Article
• Language: English
• Published: Australia Elsevier Ltd 01.08.2023; Elsevier BV; Elsevier Limited
• Subjects: Cross-education; Education; Elbow; Exercise; Humans; Influence; Muscle hypertrophy; Muscle Strength; Muscle, Skeletal; Research design; Resistance Training; Strength training; Ultrasonic imaging; Within-subject model; Muscle strength; Cross-education; Muscle hypertrophy; H1; BAIN; cm; H2; H3; 1RM; HU; Within-subject model
• ISSN: 1440-2440; 1878-1861; 1878-1861
• DOI: 10.1016/j.jsams.2023.06.011

Within-subject training models have become common within the exercise literature. However, it is currently unknown if training one arm with a high load would impact muscle size and strength of the opposing arm training with a low load. Parallel group. 116 participants were randomized to one of three groups that completed 6-weeks (18 sessions) of elbow flexion exercise. Group 1 trained their dominant arm only, beginning with a one-repetition maximum test (≤5 attempts), followed by four sets of exercise using a weight equivalent to 8–12 repetition maximum. Group 2 completed the same training as Group 1 in their dominant arm, while the non-dominant arm completed four sets of low-load exercise (30–40 repetition maximum). Group 3 trained their non-dominant arm only, performing the same low-load exercise as Group 2. Participants were compared for changes in muscle thickness and elbow flexion one-repetition maximum. The greatest changes in non-dominant strength were present in Groups 1 (Δ 1.5 kg; untrained arm) and 2 (Δ1.1 kg; low-load arm with high load on opposite arm), compared to Group 3 (Δ 0.3 kg; low-load only). Only the arms being directly trained observed changes in muscle thickness (≈Δ 0.25 cm depending on site). Within-subject training models are potentially problematic when investigating changes in strength (though not muscle growth). This is based on the finding that the untrained limb of Group 1 saw similar changes in strength as the non-dominant limb of Group 2 which were both greater than the low-load training limb of Group 3.