- Running strengthens muscular and cardiovascular endurance, mainly involving calves, quads, glutes and hamstrings, and excluding other muscle groups.
- Running works on slow muscle fibers, while strength training stimulates fast fibers, developing muscle power and balance.
- To improve performance and prevent injury, integrating at least one day of strength training per week is critical for a complete workout.
Running, especially on uneven terrain or hilly trails, requires not inconsiderable muscular effort for the legs. But can running be compared with classic strength training dedicated to the legs and replace leg day at the gym? To answer the question, one must first understand how running affects the muscles compared to gym training.
The muscles involved in running
Running is an activity that engages muscles throughout the body while focusing primarily on lower body muscles, such as calves, hamstrings, glutes and quads. The upper body and core are also involved, contributing to stability and propulsion. However, some muscles, such as the external rotators, abductors and hip adductors, may be under-stressed, except when running on off-road terrain. Biomechanics also play a role: if the glutes or hamstrings are weak, the body tends to compensate by overloading other muscles. That’s why targeted exercises to strengthen these groups can make all the difference.
Running vs. strength training: what are the differences?
Both running and strength training can strengthen the legs, but they do so in different ways: running works primarily on slow twitch (type I) muscle fibers, which are responsible for endurance and the ability to sustain prolonged effort; in contrast, specific strength training stimulates fast twitch (type II) fibers, which are essential for power and explosiveness. Another key difference is the use and increase of overload: in the gym, you gradually increase weight or repetitions to stimulate muscle growth; in running, this type of progress occurs only as you introduce specific sessions such as intervals uphill.
Is running alone enough to strengthen the legs?
Running can improve muscular endurance, but it is not enough to develop strength and muscle mass in a balanced way. Incorporating targeted workouts, such as intervals uphill or high-intensity sessions, can certainly help build power, but it will not be enough to offset the need for strength exercises. In addition, focusing solely on running can lead to muscle imbalances, increasing the risk of injury and reducing the efficiency of running itself.
The role of running in leg training
Running and targeted leg training have different but complementary goals. Running strengthens endurance, hence muscular and cardiovascular endurance, but does not offer the full muscle stimulation you get in the gym. Integrating at least one day devoted to legs into your weekly routine can help you improve performance, prevent imbalances, and reduce the risk of injury. Balancing the two types of training is key: during periods of intense training or high mileage, you might reduce strength work to avoid overtraining. The off season is the best time to focus more on strength exercises to prepare for the new season.
The role of running in training the legs
Running helps to work and build muscular endurance and strength, but it does not eliminate the need to devote targeted leg training. If your legs feel fatigued after a run, it means that it also worked as a muscle workout. If not, it was more of an aerobic activity that helped build endurance. To optimize performance and maintain muscle balance, incorporating strength training into your routine can lead to significant benefits.