High Intensity Interval Training: Is It Suitable for Youth Athletes?

High intensity interval training (HIIT) consists of repeated bouts of brief, intermittent high-intensity exercise, interspersed by periods of rest or low-intensity exercise. It has been used by athletes to improve performance for over 100 years. HIIT is time-efficient, and is recognized as effective in increasing performance among adult athletes. Further, there are well-established training guidelines for adults. In youth athletes, several studies have demonstrated the feasibility of HIIT in improving aerobic power and performance, although the effectiveness of HIIT appears to be lower than in adults. Additionally, the effectiveness of HIIT in improving other performance measures (e.g., sprint, explosive power) in young athletes is inconsistent.

The time-efficient nature of HIIT makes it attractive for both adult and youth athletes. For youth, however, HIIT may be specifically suitable. Children appear to perceive less fatigue during short bursts of high-intensity exercise, compared with adults. The intermittent nature of HIIT is also more aligned with children’s physical activity pattern, which is typically characterized by brief, high-intensity bouts of activity. Recovery is an integral aspect of HIIT, so children’s distinctive faster recovery from high-intensity exercise may allow them to take better advantage of HIIT protocols.

It has been suggested that children typically activate their type-II motor units to a lesser extent than adults. That is, they rely more on their oxidative, type-I motor units. HIIT, characterized by high-intensity bouts, requires athletes to utilize more of their type-II motor units. Thus, HIIT, where the intensity is sufficiently high, may provide youth athletes with the opportunity to activate and train more of their type-II and, specifically, type-IIa motor units, and to better develop the aerobic potential of these motor units. However, it is suggested that in order to fully exploit this potential benefit of HIIT, the effective training zone for young athletes must be higher than in adults. That is, while HIIT may be feasible and suitable for youth athletes, in order to increase its effectiveness exercise intensity must be higher than is typically recommended for adults. Thus, youth-specific training guidelines for HIIT must be developed.