This is an excerpt from Practical Guide to Exercise Physiology-2nd Edition by Robert Murray & W. Larry Kenney.
This topic is covered briefly in chapter 8, and it’s good news for endurance athletes. The short story is that the benefits of endurance training are not reduced by strength training (but the benefits of strength training can be blunted by too much endurance training). A well-designed strength training program can help endurance athletes maintain or even build muscle mass, an important adaptation during long training seasons.
Although endurance runners and cyclists are often lean, maintaining adequate muscle mass is important for sustaining performance. Loss of muscle mass due to heavy training and inadequate energy (caloric) intake will impair performance. A 30-minute strength training program conducted twice each week can be enough to help prevent the loss of muscle mass.
Open-water swimmers, triathletes, cyclists, and cross-country skiers are good examples of endurance athletes for whom upper- and lower-body musculature is important for success in their sports. Both off-season and in-season strength training are essential for increasing strength and preserving or enhancing muscle mass, adaptations that allow endurance athletes to train and compete at higher levels.
As an example, if a distance swimmer’s maximal strength in the latissimus dorsi before a competitive season is 100 pounds (45 kg) and each race requires the swimmer to exert 65 pounds (30 kg) with each arm stroke, the swimmer is repeatedly using 65% of maximal strength. If that swimmer were able to increase maximal strength in the latissimus dorsi to 120 pounds (54 kg), swimming at the same pace would require only 54% of maximal strength, making the effort easier. If the swimmer picked up the pace to use 65% of the new maximal strength, the applied force would be 78 pounds (35 kg), enabling the swimmer to go faster at the same relative effort as before.
Performance Nutrition Spotlight
Training with low muscle glycogen stores has been shown to increase oxidative enzymes involved in carbohydrate and fat oxidation, adaptations that often lead to improved endurance performance. This “train low” strategy should be used only periodically because the capacity for training is dramatically reduced in times of low muscle glycogen. In addition, it is helpful for athletes to increase their protein intake when training with low glycogen to ensure they stay in positive protein balance.
Suggestions for Combining Endurance and Strength Training
- Keep an eye on daily fatigue levels whenever athletes combine intense strength training with demanding endurance training in the same week. Reduce workload if training performance begins to suffer.
- After a hard session of strength training, athletes should ideally have at least 12 hours of recovery before undertaking endurance training.
- Sufficient time is needed after demanding sessions of strength training to allow for recovery of proper running, cycling, or swimming mechanics.
- If possible, plan endurance training before strength training. For example, do endurance training in the morning, with strength training in the afternoon or evening.
- When athletes shift their focus to endurance training, one or two strength workouts per week is enough to maintain muscle strength.
- Vary the mode, duration, and intensity of strength training to optimize adaptations and prevent strength training from interfering with endurance adaptations.
References: Berryman, N. et al. 2018. Strength training for middle- and long-distance performance: a meta-analysis. Int J Sports Physiol Perform. 13(1):57-63.
Doma, K. et al. 2019. Training considerations for optimising endurance development: an alternate concurrent training perspective. Sports Med. 49(5):669-682.