Endurance training is known to improve cardiorespiratory function as well as glycogen storage and oxidative capacity of muscle tissue. Strength training causes muscle hypertrophy and improved strength, and a specific type of training known as explosive strength training may lead to increased motor unit activation.
The researchers wanted to find out the effects of simultaneous endurance training and explosive strength training on 5k running performance, muscle power, and aerobic power. Well-trained endurance athletes participated in the study. Eighteen endurance athletes were divided into two groups, experimental and control, and trained for 9 weeks. Both groups had the same training volume, but the experimental group had 1/3 of their workouts changed to explosive strength training techniques. Before and after 6 and 9 weeks of training, all athletes completed a 5k run.
Results showed that before the training period, 5k running time did not differ significantly between the groups. After training, significant differences were found. Running time decreased in the experimental group whereas no changes were seen in the control group. Interestingly, the improvements in running time in the experimental group occurred without any changes in their VO2max. In fact, there was a negative correlation between individual changes in VO2max and changes in 5k speed. This result supports the hypothesis that endurance athletes; performance is limited not only by VO2max but also by muscle power. The improvements in running time have been attributed to improved neural factors such as motor activation, as well as improved running economy.