Running Hill Intervals

When incorporating high-intensity interval training (HIIT) into your running, it’s essential to consider the length of the repetitions, the intensity and the recovery intervals in between. These factors put different physical and physiological stresses on the body. In HIIT, we refer to the repetition as the "work phase" and the rest period as the "recovery interval."

Your goal for any interval session should be to target a specific physiological component of your fitness, whether that’s your nervous system, cardiovascular system, musculature or energy systems.

Modern interval training has evolved to target various physical outcomes. Most runners have likely incorporated some form of interval training into their routines, and one common session is hill sprints. Hill sprints primarily target the nervous system and muscle fibres designed to generate high levels of strength. Understanding the intensity and appropriate recovery period between hill sprints is key to maximizing benefits.

How to structure your sessions:

Short Hill Sprints (6-12 seconds):

These quick bursts up a steep hill (about 50 meters or less) are designed to stimulate the nervous system by recruiting all available muscle fibres. This results in improved stride rate and overall running efficiency. This workout is primarily anaerobic, relying on the creatine phosphate system for energy. The creatine phosphate system provides about 50% of the energy for sprints lasting 6-12 seconds. However, this system depletes quickly and requires 10-15 seconds to regenerate. To get the most out of your hill sprints, it’s crucial to allow the system to replenish.

If you want to maintain maximal intensity in each sprint, ensure you’re allowing enough time for full regeneration of the creatine phosphate stores, typically 3 minutes of rest. Without proper recovery, the sprints will lose their effectiveness, and you may experience fatigue that lasts for days.

Longer Hill Repeats (1m - 4 minutes)

These hill repeats are typically performed up a moderately steep hill at your 3-5k pace, and they target your aerobic energy production and intermediate fast-twitch muscle fibres. These fibres are crucial for mid-distance races, like the 10k. Longer hill repeats require longer recovery intervals—usually 1 to 3 times the length of the repetition. If you cut the recovery time short, the workout will become too anaerobic, diminishing its effectiveness for building endurance.

The best recovery strategy? Jog slowly down the hill, and be sure to walk at the bottom until you feel fully recovered.

Conclusion:

Hill sprints are a powerful tool for improving both your strength and endurance, but they need to be respected. Ensure you’re giving yourself ample recovery time between efforts to get the full benefit, and always adjust the intensity to match your goals. By focusing on recovery and proper pacing, you can optimize your training and improve both your power and aerobic capacity.

Bevan McKinnon / March 2025