Comparative Effects of High-Intensity Interval and Functional Training on Performance Outcomes in Adolescent Female Volleyball Players

Volleyball is a high-intensity intermittent sport characterized by repeated explosive actions such as jumping, sprinting, accelerating, decelerating, and rapid changes of direction, combined with frequent technical maneuvers including serving, setting, spiking, and blocking. These actions require sustained neuromuscular output while maintaining technical precision under fatigue, placing substantial demands on both aerobic and anaerobic energy systems. Aerobic capacity is critical for sustaining recovery between rallies and maintaining performance throughout long matches or tournaments, whereas anaerobic power and strength are essential for explosive efforts that dominate competitive play. Additionally, agility, reactive strength, and coordination contribute significantly to performance, particularly in adolescent players who are still developing physiologically.

Given these demands, volleyball training requires conditioning approaches that are both time-efficient and sport-specific. Traditional continuous endurance training has been criticized for its poor transferability to volleyball, as it fails to replicate the intermittent, high-intensity, and multidirectional nature of the game. In contrast, modern approaches such as high-intensity interval training (HIIT) and high-intensity functional training (HIFT) have emerged as promising strategies. HIIT, involving repeated near-maximal bouts interspersed with structured recovery, has been shown to improve both aerobic and anaerobic capacity, enhance repeated sprint ability, and optimize recovery kinetics. However, resistance-based HIIT often emphasizes traditional strength exercises performed in a format with fixed rest intervals, which may not fully capture the sport-specific, multidirectional, and reactive movement patterns required in volleyball.

HIFT has been introduced as an integrative and multimodal training approach that combines plyometric drills, bodyweight resistance, agility exercises, and functional movements into circuit-based formats performed at high intensity with minimal recovery. Unlike resistance-based HIIT, which primarily involves structured strength exercises performed in a circuit format with fixed rest intervals, HIFT emphasizes more varied, compound, and task-oriented exercises that more closely mirror the sport-specific demands of volleyball. These exercises not only target cardiovascular fitness but also simultaneously improve explosive power, neuromuscular coordination, and stability. This integrative nature makes HIFT particularly promising for adolescent volleyball players, where physical conditioning must also support technical skill development and injury prevention.

Despite the growing use of both HIIT and HIFT in applied practice, direct experimental comparisons between these modalities in youth volleyball players are limited. Adolescence represents a critical developmental window where training adaptations can have long-term effects on physical performance, neuromuscular coordination, and resilience. Therefore, identifying the most effective training model for enhancing multidimensional performance in young female athletes is of high practical and scientific importance.

The present randomized controlled trial was designed to compare the effects of 12 weeks of HIIT and HIFT on performance outcomes in adolescent female volleyball players. Thirty-two licensed athletes aged 15-18 years, competing in a regional league, were randomly allocated into three groups: HIIT (n=10), HIFT (n=11), and a control group (n=11). All groups continued routine volleyball training (3-4 sessions per week). In addition, the intervention groups performed two supervised conditioning sessions weekly for 12 weeks, while the control group engaged in additional volleyball practice sessions to balance training volume.