High-Intensity Interval Training (HIIT) has taken the fitness world by storm in recent years, with reports suggesting that its adoption has increased by over 50% in the last decade among fitness enthusiasts and athletes alike. Once the preserve of elite athletes, it has now become a staple in mainstream fitness, praised for its efficiency and effectiveness. From gym-goers looking to burn fat to athletes aiming to boost performance, HIIT offers something for everyone. However, not all HIIT protocols are created equal, and understanding their nuances is key to maximising results for their clients.

The Rise of HIIT Training

HIIT’s popularity lies in its promise: shorter workouts with significant benefits. By alternating between intense bursts of exercise and short recovery periods, HIIT provides a potent cardiovascular and metabolic workout. Its benefits include improved VO2max, fat loss, and time efficiency, making it particularly appealing in today’s busy world.

Research consistently supports HIIT as an effective method for improving fitness and health. For instance, a meta-analysis by Scribbans et al. (2016) highlighted that HIIT can lead to significant improvements in VO2max and metabolic health, often outperforming traditional moderate-intensity continuous training. For example, the widely studied Tabata protocol (20 seconds of all-out effort followed by 10 seconds of rest, repeated for 4 minutes) demonstrated substantial improvements in both aerobic and anaerobic fitness when compared to moderate-intensity training. The variety of HIIT formats available ensures programmes can meet the diverse needs and preferences of clients.

HIIT Protocols and Supporting Research

1. Tabata Protocol

Developed by Dr Izumi Tabata, this protocol involves eight rounds of 20 seconds of maximal effort followed by 10 seconds of rest. Research shows this method can significantly improve VO2max and anaerobic capacity in as little as four minutes per session.

2. Sprint Interval Training (SIT)

SIT protocols often consist of fewer, longer intervals. A study by Gibala et al. (2012) found that 30-second all-out sprints with four minutes of recovery between bouts can improve aerobic and anaerobic fitness significantly, even when performed for just a few weeks.

3. Extended HIIT Protocols

As seen in the study by Sonchan et al. (2025), longer intervals such as 40-second or 60-second sprints with appropriate recovery times provide substantial benefits for VO2max improvement, particularly in recreational athletes.

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HIIT: Not Just Running

HIIT training can be adapted to various exercises, making it suitable for diverse clients. This adaptability caters to different fitness levels, preferences, and goals, ensuring that every individual can engage in a challenging yet enjoyable workout. Some popular options include:

  • Running: Sprints on a track or treadmill.
  • Bodyweight Exercises: Burpees, mountain climbers, or squat jumps.
  • Cycling: All-out efforts on a stationary bike.
  • Rowing: High-intensity bursts on a rowing machine.
  • Functional Training: Incorporating kettlebells or resistance bands for interval work.

By mixing modalities, workouts can remain engaging and cater to clients with different preferences and needs.

Insights from the Sonchan Study

The study by Sonchan et al. (2025) evaluated three HIIT protocols (20/20, 40/10, and 60/5) over six weeks.

  • HIIT20/20: 20 metres sprint with equal rest intervals.
  • HIIT40/10: 40 metres sprint with shorter rest intervals.
  • HIIT60/5: 60 metres sprint with minimal rest intervals.

These intervals were chosen to explore the effects of varying sprint durations and rest periods, with the aim of identifying the most effective combination for improving VO2max in recreational athletes. Longer intervals such as 40/10 and 60/5 are believed to place greater demands on aerobic and anaerobic systems, aligning with prior evidence that extended high-intensity efforts can produce superior cardiovascular adaptations. Thirty-one recreational football players participated, training three times weekly. VO2max was measured pre- and post-intervention, along with leg strength.

Key Findings:

  • VO2max: The HIIT40/10 and HIIT60/5 protocols significantly improved VO2max by 10.4% and 12%, respectively.
  • Leg Strength: No significant improvements were observed in leg strength across any protocol.
  • Correlation: A weak but noteworthy correlation was identified between VO2max and leg strength, suggesting that improvements in one may indirectly benefit the other.

These results highlight the importance of selecting the right protocol based on training goals. For VO2max improvements, HIIT40/10 or HIIT60/5 proved superior to shorter intervals like HIIT20/20.

Periodised HIIT Programme

Based on the study’s findings, here’s a six-week programme for clients aiming to improve VO2max:

Week 1-2:

  • Warm-up: 5 minutes of dynamic stretching and light jogging.
  • HIIT Protocol: 6 rounds of 40-second sprints with 10 seconds rest.
  • Cool-down: 5 minutes of light jogging and static stretches.

Week 3-4:

  • Warm-up: Same as Weeks 1-2.
  • HIIT Protocol: 8 rounds of 40-second sprints with 10 seconds rest.
  • Cool-down: Same as Weeks 1-2.

Week 5-6:

  • Warm-up: Same as earlier weeks.
  • HIIT Protocol: 10 rounds of 60-second sprints with 5 seconds rest.
  • Cool-down: Same as earlier weeks.

The Versatility and Benefits of HIIT

HIIT training’s benefits are undeniable: improved cardiovascular health, enhanced fat burning, and time efficiency. Whether it’s sprinting on a track, cycling indoors, or performing bodyweight exercises, the possibilities are endless. By understanding the science and tailoring programmes to client goals, we can maximise the potential of this versatile training method. The Sonchan study illustrates the effectiveness of structured interval designs like HIIT40/10 and HIIT60/5 for improving VO2max, while the adaptability of HIIT allows for the utilisation of various exercises to cater to diverse client needs. With these insights, HIIT can be confidently implemented into programmes with the aim of achieving cardiovascular and metabolic improvements efficiently.

By staying informed and creative, clients reap the rewards of HIIT training in all its forms.

References

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