Peak velocity during concentric and eccentric muscle actions in the peck deck exercise

Velocity loss in resistance exercise can be an indicator of fatigue and proximity to concentric failure.  However, there is a lack of studies in the literature describing the peak velocity of concentric and eccentric muscle actions during  repetitions through sets. OBJECTIVE: Describe and compare the repetitions peak velocity in the concentric and eccentric muscle actions in the Peck-Deck exercise performed until failure with 75% 1 repetition-maximum (1RM). METHODS: Twenty-five healthy and well-trained participants (age: 24,16 ± 4,61 yrs; body mass: 69,38 ± 10,17 kg; height: 1,68 ± 0,08 m; peck deck 1RM: 82,68 ± 27,64 kg) without any musculoskeletal disorders in the 12 months prior to participating in this study. Two visits were conducted with each participant, with a minimum of two days between them. In the first visit, a 1RM test was performed. In the second, two sets were performed until concentric failure with 75% 1RM. The sets were recorded using a smartphone camera, in a transverse plane, and later analyzed using the Kinovea (version 2023.1.1). The peak velocity was measured in the first repetition (1st), second repetition (2nd), last valid repetition (full range of motion), and the repetition in which failure occurred, in both the concentric and eccentric muscle actions of the first set. A repeated measures ANOVA was conducted to compare the peak velocity of each repetition, followed by a Tukey post-hoc test to determine pairwise differences using jamovi (version 2.5.6.0). RESULTS: Statistically significant differences were found between peak velocity of the first and last valid repetitions [F(7, 168) = 49,5; p < 0,001], first and failure repetition [F(7, 168) = 49,5; p < 0,001], second and last valid repetition [F(7, 168) = 49,5; p < 0,001]; second and failure repetition [F(7, 168) = 49,5; p < 0,001] in concentric muscle action.