title: Chain-loaded variable resistance warm-up improves free-weight maximal back squat performance.
abstract: The acute influence of chain-loaded variable resistance exercise on subsequent free-weight one-repetition maximum (1-RM) back squat performance was examined in 16 recreationally active men. The participants performed either a free-weight resistance (FWR) or chain-loaded resistance (CLR) back squat warm-up at 85% 1-RM on two separate occasions. After a 5-min rest, the participants attempted a free-weight 1-RM back squat; if successful, subsequent 5% load additions were made until participants failed to complete the lift. During the 1-RM trials, 3D knee joint kinematics and knee extensor and flexor electromyograms (EMG) were recorded simultaneously. Significantly greater 1-RM (6.2 ± 5.0%; p < .01) and mean eccentric knee extensor EMG (32.2 ± 6.7%; p < .01) were found after the CLR warm-up compared to the FWR condition. However, no difference (p > .05) was found in concentric EMG, eccentric or concentric knee angular velocity, or peak knee flexion angle. Performing a CLR warm-up enhanced subsequent free-weight 1-RM performance without changes in knee flexion angle or eccentric and concentric knee angular velocities; thus a real 1-RM increase was achieved as the mechanics of the lift were not altered. These results are indicative of a potentiating effect of CLR in a warm-up, which may benefit athletes in tasks where high-level strength is required.
authors.affiliation: a Sport, Outdoor and Exercise Science , University of Derby , Buxton , UK.
authors.forename: Minas A
authors.initials: MA
authors.lastname: Mina
authors.affiliation: b Centre for Exercise and Sports Science Research, School of Medical and Health Sciences , Edith Cowan University , Joondalup , Western Australia.
authors.forename: Anthony J
authors.initials: AJ
authors.lastname: Blazevich
authors.affiliation: c Department of PE & Sport Science , University of Thessaly , Trikala , Greece.
authors.forename: Giannis
authors.initials: G
authors.lastname: Giakas
authors.affiliation: d French Rugby League Academy , Toulouse , France.
authors.forename: Laurent B
authors.initials: LB
authors.lastname: Seitz
authors.affiliation: e Sport, Exercise & Life Sciences , University of Northampton , Northampton , UK.
authors.forename: Anthony D
authors.initials: AD
authors.lastname: Kay
mesh_terms: D000328:Adult; D018592:Cross-Over Studies; D004576:Electromyography; D006801:Humans; D007717:Knee / Q000502:physiology; D008297:Male; D018482:Muscle, Skeletal / Q000502:physiology*; D014891:Weight Lifting / Q000502:physiology*; D055815:Young Adult
keywords: 1-RM; PAP; accommodating resistance; preconditioning; strength training