Physical performance adaptations following a 10-week pre-season in senior rugby players

This study was designed to explore the longitudinal changes in lower-limb isometric and eccentric strength, vertical jump performance, and sprint speed under similar training regimes but across different positional roles (forwards vs. backs). Participants completed an ≈8-week pre-season program (≈4 sessions/week) comprising training blocks (plyometrics/ballistics, sprint-speed, resistance, endurance); testing was performed one week before and one week after the program. Twenty-four highly trained male rugby players volunteered to participate in the study and were subsequently classified into backs (n = 11, height: 1.79 ± 0.04 m, body mass [BM]: 79.0 ± 5.9 kg) and forwards (n = 13, height: 1.87 ± 0.06 m, BM: 100.0 ± 10.3 kg). Participants completed a testing battery including a 30-meter (m) linear sprint, vertical jump assessments, and lower-limb strength measures: isometric calf (ISO CALF ), hip adduction (ISO ADD ) and abduction (ISO ABD ), hamstring at 90°–20° (ISO 90–20 ), and eccentric hamstring strength via the Nordic hamstring exercise (NHE). Sprint performance improved only in backs (p = 0.022; ES = −0.85). Isometric and eccentric strength assessments demonstrated consistent reductions in maximum impulse for ISO ADD and ISO ABD , irrespective of task, limb, or positional group. Conversely, only backs showed significant increases in maximum force (p = 0.002 to 0.059; ES = 0.71 to 1.41) in ISO CALF , ISO 90–20 , and NHE across both limbs. In conclusion, these findings suggest that, during the initial pre-season period, backs exhibited more favorable sprint and strength adaptations to a general training program than forwards.