It is a common belief that athletes should skip the weight room during their season out of fear it will cause fatigue and hurt performance. But is that actually true? Most sports demand some combination of strength, power, agility, acceleration, deceleration, endurance, and speed. The coaching world has a name for what happens when you stop training those qualities: the Principle of Reversibility, or "use it or lose it."
The power equation
Power = Strength × Speed. During practice, athletes train the speed side of that equation, but without the strength work in the gym, the strength side goes unaddressed. If strength declines over the course of a season, power production can decline with it, right when athletes need to be performing at their best heading into the playoffs. The good news: strength training just 1-2x per week while in-season is enough to keep the strength side of the equation climbing, not just holding steady.
What the research shows
Strength training does not just build muscle, it also places meaningful stress on the bones, tendons, and other connective tissues that have to tolerate the demands of competition. In a study of 30 young elite female soccer players, half completed a 12-week, twice-weekly progressive in-season strength program. Of the 13 non-contact injuries reported during the season, 2 occurred in the strength-training group compared with 11 in the traditional-training-only group (Darragi et al., 2024).
The bottom line
Strength training in-season does not just maintain force production and power output; it keeps the muscles and connective tissues resilient enough to absorb the high forces a sport demands, which is a meaningful part of injury prevention on its own.
References
Darragi et al., 2024, "Effects of In-Season Strength Training on Physical Fitness and Injury Prevention in North African Elite Young Female Soccer Players." de Hoyo et al., 2015, eccentric-overload training and injury prevention in junior elite soccer players. Gual et al., 2016, inertial resistance training for patellar tendinopathy risk. Panagoulis et al., 2018, in-season neuromuscular strength training in early-adolescent soccer athletes. Taylor et al., 2017, "Activity Demands During Multi-Directional Team Sports."