You worked out yesterday, and today your muscles are on fire. That doesn't mean you seriously hurt yourself, but it does mean your muscles suffered some damage and need time to recover before your next workout. By giving them enough time to rest, they'll be even stronger the next time you hit the gym.
Muscle Damage and Recovery
Strength training damages your muscles. The damage may be small, limited to a few protein molecules, or it may be large enough to disrupt entire muscle fibers, the cells within your muscles. While that may sound bad, it's how muscles get stronger. Exercise scientists don't yet fully understand how the process works, but inflammatory signals and protein synthesis play a role. Protein synthesis remains elevated for 48 hours after a strength-training workout. Because your muscles are hard at work rebuilding themselves between workouts, they need enough recovery time to complete repairs before getting stressed again.
The heavier the loads you're lifting and the more intense your workouts are, the more recovery time you'll need. Lower-body exercises and compound, multijoint exercises take longer to recover from than upper-body and single-joint exercises. Also, the older you are, the more recovery time you'll need. Even the type of muscle fibers you target in your workout play a role. Fast-twitch muscle fibers recover more slowly than slow-twitch fibers.
Programming for Recovery
For most recreational athletes, simply spacing strength-training workouts throughout the week works well as a recovery strategy. If you want to get into the gym more often, a split routine can also give your muscles enough recovery time. For instance, you could train your lower body on Monday, hit your upper body on Tuesday, come back to the legs on Wednesday, and work your arms on Thursday. Split routines allow you to maximize your time in the gym while still giving individual muscles enough rest time between workouts.
The American College of Sports Medicine (ACSM) recommends allowing at least 48 hours to recover between strength-training sessions for any individual muscle group. After a very high-intensity weight-training session, you may need to allow 72 hours or even more. ACSM suggests two or three strength-training sessions per week for most individuals. Because aerobic exercise doesn't cause the sort of muscle fiber damage that strength training does, you can schedule aerobic workouts more frequently. ACSM suggests five or more days per week of moderate-intenisty aerobic exercise.
- Essentials of Strength Training and Conditioning; National Strength and Conditioning Association
- Medicine and Science in Sports and Exercise: Quantity and Quality of Exercise for Developing and Maintaining Cardiorespiratory, Musculoskeletal, and Neuromotor Fitness in Apparently Healthy Adults: Guidance for Prescribing Exercise; American College of Sports Medicine
- Exercise Physiology for Health, Fitness and Performance; Sharon A. Plowman and Denise L. Smith
- The Journal of Strength and Conditioning Research: Does Exercise-Induced Muscle Damage Play a Role in Skeletal Muscle Hypertrophy?; Brad Schoenfeld
Joe Miller started writing professionally in 1991. He specializes in writing about health and fitness and has written for "Fit Yoga" magazine and the New York Times City Room blog. He holds a master's degree in applied physiology from Columbia University, Teacher's College.