Jan. 20, 2000 (Atlanta) -- Optimal fitness seekers must decide if their #1 goal is strength or endurance. According to Michael Leveritt, PhD, from the Centre for Sport and Exercise Science at Waikato Polytechnic in Hamilton, New Zealand, if it's strength they're after, they should skip the running. Those who train for both types of fitness will probably be disappointed.
"Strength gains during combined strength and endurance training are not likely to be as great when compared with strength gains achieved through strength training alone," Leveritt tells WebMD.
For his report, which appears in the December issue of Sports Medicine, Leveritt studied previous research that looked at concurrent training. Although he says that the comparisons were often difficult because of varying study methods and fitness levels of participants, one overriding principle did emerge: Increases in strength will suffer if endurance exercise is attempted at the same time.
Not only are the physiological effects from strength or resistance and endurance training different, says Leveritt, but sometimes they may even be opposite. He cites numerous studies that show endurance training contributing to a loss in strength and decreased muscle-fiber size. "What might be happening," he tells WebMD, "is that when individuals perform a bout of strength training after they have done some endurance training -- even on the preceding day -- the quality of training and/or the physiological response to the strength training may be less than optimal." He notes, on the other hand, that he discovered instances in which resistance training can cause an increase in both.
According to Leveritt, running seems to have the greatest negative effect on strength when combined with training geared towards building strength. He found inconsistent results when cycling was studied. The two exercises that have the least negative effect on strength are endurance rowing and hand cranking.
The probable reasons given by Leveritt for combination training's negative effect on strength include:
- contrasting effect on muscle fibers of the various exercises.
- differences in hormonal needs for both types of exercise.
- differences in demands placed on the neuromuscular system during endurance and strength training.
- differences in level and type of fatigue. "There is evidence to suggest that residual fatigue from a bout of prior endurance exercise inhibits the quality of subsequent strength exercise," writes Leveritt.
Leveritt says that most of this advice applies to trained, high-performance athletes and does not mean that average, everyday people should not try to improve their strength and endurance. "While this may be a big issue for a finely tuned athlete needing to have maximum levels of both strength and endurance," Leveritt tells WebMD, "it may not be of great consequence to an average member of the public seeking to improve general health and well-being by undertaking an exercise program involving both strength and endurance training."
The American College of Sports Medicine agrees. According to a recent position paper they published, it's important that individuals do both cardiovascular (endurance) training to improve the heart and lungs and resistance training to improve muscular strength. No expert would disagree that both muscular development and cardiovascular health are important.
"Resistance and endurance training both improve physical capacity and health ... depending on the goals of the person, but current guidelines for exercise prescription suggest that both be done to improve physical capacity," Donna Terbizan, PhD, tells WebMD. Terbizan is a research scientist in the Health, Physical Education and Recreation Department at North Dakota State University in Fargo.
Resistance training helps make improvements such as increased skeletal muscle bulk, increased connective tissue amount and strength, increased bone density, and increased muscle attachment size. Strength training can also increase fat-free weight and decrease body-fat levels. Having additional muscle mass may increase resting metabolism, which plays an important role in increasing energy expenditure. All of these changes are beneficial in decreasing the chance for obesity, osteoporosis, diabetes, cardiovascular disease, and, in older people, the number of falls.
- The muscles adapt to strength and endurance training differently.
- The most effective method of developing strength or endurance is to train for one or the other, but not both.
- At less than maximum levels of performance, people can engage in both strength and endurance training without negative effects.
- Don't train at high levels for both strength and endurance at the same time.