Brad Lambert, Ph.D, CSCCA-SCCC
For optimal health and fitness, the American College of Sports Medicine recommends both resistance and endurance exercise regularly. Both forms of exercise provide specific benefits for one’s health. Endurance exercise such as jogging or biking has been found to increase aerobic fitness, reduce body fat, and aid in the prevention of a number of metabolic diseases. Resistance exercise is typically found to increase muscle mass, muscular strength, bone density, and motor function. However, it has been shown that when combined, endurance and resistance training can result in reduced overall gains compared to whether either form of exercise training alone. This phenomenon is often referred to an “interference effect” by exercise scientists. Typically, muscle adapts to a given training form. For instance, resistance training leads to an adaptation to handle greater loads and produce more force than endurance training. The latter causes muscle adaptation to have greater resistance to fatigue and an increased ability to process oxygen. Therefore, training for both strength/muscle mass and endurance creates a situation where muscle is being stimulated to adapt into opposing functional and metabolic directions. By and large, the literature suggests that endurance exercise training interferes with resistance training gains more strongly than vice versa. In other words, if one wants to become strong and powerful, it may not be a good idea to add a great deal of long distance running to one’s exercise training plan. However, our research group in the Applied Exercise Science Lab has some interesting new data which suggest that not all forms of endurance exercise interfere with the gains of resistance training.
Over the past few years, our lab group has observed aquatic treadmill running, a new form of low impact endurance exercise that unloads one’s joints while providing lateral water resistance during running. Briefly, aquatic treadmill running involves running in water at chest depth on a motorized treadmill belt with water jet resistance. Our investigation compared aquatic and land treadmill running -with and without resistance exercise using 47 general population participants. The findings showed that those who vigorously ran on the aquatic treadmill immediately following resistance exercise (2/wk) and once per week without the combination of resistance training for 12 weeks had significantly greater gains in muscle mass and strength compared to participants who only performed land treadmill exercise following resistance training, or resistance training alone. The participants who performed aquatic treadmill running also significantly improved their aerobic fitness as well. Therefore, at this time the “interference” effect does not appear to hold true for all modes of endurance exercise. This and other research may contribute to greater commercial availability of aquatic treadmill technology. In the meantime, our laboratory is continuing to investigate the physiologic responses to combined resistance and aquatic treadmill training at the cellular level.