So long as I taper sufficiently before a race, I feel they improve my performance. But training for endurance and training for maximal strength and power represent completely different and opposite forms of activity. Endurance training consists of many thousands of submaximal muscle contractions performed at low to moderate workloads, while training for strength and power involves relatively few contractions at maximal or near maximal force. From a physiological standpoint, it seems unlikely that muscle would be able to adapt to two seemingly incompatible training stimuli when they are undertaken simultaneously. Surprisingly, few good scientific studies have been conducted using well-trained athletes to determine if the improvements in muscular strength gained from resistance training result in enhanced endurance performance.
Swimming is one sport where the majority of competitors practice some form of resistance training.
Although most competitive swimming distances might not be considered true endurance events, elite swimmers perform huge volumes of over-distance training. To determine whether adding resistance training to pool training might improve sprint-swim performance, Tanaka, et al. The swimmers were divided into two groups of 12 swimmers and matched for stroke specialities and performance. The two groups performed all swim training sessions together for the duration of the season, but in addition to the pool training, one group performed resistance training three days a week, on alternate days for eight weeks. The resistance training program was intended to simulate the muscles employed in front crawl swimming and utilized weight lifting machines as well as free weights.