Effects of Resistance Training With High vs. Light-moderate Loads on Muscle-tendon Function in the Elderly

The decline in muscle function provoked by the aging process and frailty are directly related to decreases in mobility and the ability to perform the so called "daily life activities". Resistance training is especially useful at this stage, given that it is an effective and widely applicable intervention to control and revert sarcopenia, and the deterioration of tendon and bone function. Despite of the effectiveness of heavy load resistance training, a controversy has arisen in the last years about the effects of lower load resistance training programs to achieve similar adaptations. This is because most of the studies that have compared light-moderate versus heavy load programs did not control the differences in total training load, measured as the overall mechanical work performed during the training program. Therefore, there are no unbiased studies that have analyzed the effects of resistance training with traditional, heavy versus light-moderate loads on muscle, tendon and bone in elderly people. The purpose of the present study is to assess the effects on muscle mass and function, tendon and bone of two different training intensities, light-moderate vs. heavy load, in people older than 65 years old. The studies will be carried out with a crossover (acute training sessions) and randomized controlled design (longitudinal training intervention). Participants will perform single training sessions with each resistance training intensity and a 12-wk dynamic resistance training program on the knee extensors with different training intensities on each leg. One leg will train with heavy loads and the other one will train with light-moderate loads, but matching the load x repetitions performed by the contralateral side. Muscle adaptations (EMG, muscle size and architecture), tendon mechanical properties, bone mineral density, blood parameters and life quality will be analyzed before and after the cessation of the training program.