Impact of high-intensity interval training on tendon related gene expression in rat Achilles tendon

Immobilization or aging associated with limited physical activity can lead to the functional deterioration of tendons, which has become an important public health concern. Therefore, growing research is focused on the effect of exercise training on preserving tendon function. Exercise training subjects muscles and tendons to repeated mechanical stress, and in vitro studies have revealed that repetitive mechanical loading stimulates tendon cell responses to changes in the extracellular matrix and functional properties of the tendon. However, although several types of exercise training have been shown to be effective in preserving tendon function, no studies have investigated the impact of high-intensity interval training (HIIT), which involves composing short bouts of exercise with high-power output. Here, we determined whether the HIIT program enhanced tenogenic progressions by measuring the mRNA expression in rat Achilles tendons. Sixteen rats were randomly assigned into either a sedentary control group (Con, n = 8) or an HIIT group (n = 8). Rats in the HIIT group performed the program with treadmill running; the training volume was incremental (running speed, number of sets, and inclination), and training was conducted 5 days per week for 9 weeks. The rats in the HIIT group exhibited a marked decrease in the body weight and different types of fat weights, and a marked increase in different types of muscle weights. Real-time reverse transcription polymerase chain reaction analysis revealed that mRNA expressions of tendon-related genes Tnxb, Opn, and Tgfb1 were upregulated in the HIIT group compared to that in the Con group. Cross-links in mRNA expressions of collagen-related Dcn and Fmod in the HIIT group tended to be higher than in those Con group. These results suggest that HIIT induces initiation of tenogenic progression and stimulation of cross-link formation between collagen fibrils in rat Achilles tendons.