Longer Sprint Intervals May Improve Muscle Oxygen Utilization

Physical activities are known to engage the musculoskeletal system and result in the utilization of energy. Meaning that how the duration of rest and exercise is structured can affect the impact of SIT on physiological responses. The field of sports physiology has experienced increased interest in optimizing exercise protocols, including SIT, this attention can help to enhance the recognition of SIT’s efficacy in improving both athletic performance and overall well-being by highlighting its benefits and versatility as a tool for promoting health and fitness.

For this study, researchers from Japan, including Dr. Takaki Yamagishi from the Department of Sport Science and Research, Japan Institute of Sports Sciences and Human Performance Laboratory at the Comprehensive Research Organization at Waseda University, and Professor Yasuo Kawakami who directs the Human Performance Lab and is from the Faculty of Sport Sciences, Waseda University conducted a series of studies involving sprint interval exercises (SIE) with healthy participants to investigate and highlight the benefits of SIT.

"Establishing a minimum dose of exercise training to bring about training benefits, such as aerobic fitness, has been one of my main research interests. Due to the support from Prof. Kawakami and other co-authors, along with the collaboration with Waseda University, this unique research work using a multifaceted approach was possible,” said Yamagishi.

Two different SIE were matched for the total duration of sprint and sprint-to-rest ratio, analyzing the influence of SIE on the metabolic and physiological responses by examining the participant’s pulmonary oxygen uptake (V̇O2) levels and changes in tissue oxygenation index (∆TOI) in thigh muscles (T2-weighted magnetic resonance imaging (MRI) technique was utilized to assess the activation of thigh muscles).

According to the team, SIE20 consisting of two 20-second sprints with 160 seconds of recovery was found to outperform SIE10 consisting of four 10-second sprints with 80 seconds recovery. Both SIE protocols were found to significantly increase whole body and peripheral oxidative metabolism and activation of the major thigh muscles, however, greater peripheral oxidative metabolism was achieved with the SIE20 protocol, and the successive sprint repetitions in the SIE10 protocol did not correlate with greater oxidative metabolism. 

"In today's fast-moving world, lack of time is a major hindrance to regular physical activity. However, the exercise modalities employed in our study require less than 15 minutes to complete and provide considerable health benefits,” said Yamagishi.

"Exercise guidelines proposed by major organizations such as the American College of Sports Medicine are updated every 5 to 10 years, and we are hopeful that our study can be a part of it. Future studies on SIE can build on our findings to establish the dose-response relationship between exercise volume or intensity and the degree of training adaptations,” concluded Yamagishi.