What to train first: Balance or explosive strength? Impact on performance and intracortical inhibition.

Explosive strength and balance training are commonly applied to enhance explosive strength and balance performance. Even though both training methods are frequently implemented, ordering effects have largely been neglected. Therefore, the present study aimed to investigate ordering effects of balance and explosive strength training on explosive strength and balance performance as well as changes in short-interval intracortical inhibition (SICI). Two groups of subjects either participated in 4 weeks of balance training followed by 4 weeks of explosive strength training (BT-ET) or vice versa (ET-BT). Before, after 4 and 8 weeks, balance performance, as well as explosive strength, was tested. Additionally, SICI was tested during rest as well as during balance perturbations and explosive contractions. The results show a training specific increase in performance with an increase in balance control followed by an increase in explosive strength in the BT-ET, while the ET-BT increased its balance and explosive strength in the opposite order. There were no significant ordering effects. Both groups showed a significant decrease in SICI during the explosive contractions after the eight weeks of training. When SICI was tested during the balance perturbations, SICI initially increased after the first 4 weeks of training but returned to baseline until the end of the eight weeks. It is suggested that the decrease in SICI with prolonged training might show a disengagement of the motor cortex during the balance task. During the explosive contractions, the low SICI levels are beneficial to provide the necessary level of excitatory cortical drive.