High Intensity Interval Training (HIIT)

-High Intensity: 95%+ max effort or max HR (RPE 9-10)
-Interval Training: Periods of varying degrees of intensity/effort

This is perhaps the most “transferable” type of exercise for most ball sports. Many ball sports have time of high effort with lower effort or rest ex. Tennis, football, MMA/Boxing all have built in periods of rest. Soccer and lacrosse have less built in rest, but offer time for athletes to walk or jog, thus allowing some recovery.

HIIT should consist of intervals alternating between high intensity and low intensity (obviously). The number of rounds, work:rest ratio, and modality are highly dependent on the athlete and goal of training session. Some common methods are a 1:1 ratio for 400m repeats or 1:2 ratio for assault bike sprints. Anything with a higher rest than 1:2 is unlikely to provide the adaptations that we are searching for with HIIT. The goal is to deplete anaerobic energy systems rapidly, thus increasing metabolism which is a stressor that demands adaptation.

Practical Application:
Beginners should be hesitant and supervised when starting HIIT as it is highly stressful. Intermediate athletes should use them scattered throughout the week and have 24+ hours between sessions. Advanced athletes can do many rounds totaling 20-30 mins of work time with equivalent rest. Some athletes respond very well to this modality, others find it too difficult to recover from and use it sparingly.
As few as one round of max effort can trigger adaptations. Most bouts of effort will last between 15s-3:00. Recovery between rounds is essential because effort MUST REMAIN HIGH if adaptations are to be optimal.

Adaptations include:
ATP-PCr energy system improvement (primary up to 30s)
Glycolytic energy system improvement (primary from 30s-3:00)
Aerobic energy system improvement (especially during recovery)
Mitochondrial efficiency
Type 1 and 2 adaptations
Cardiorespiratory efficiency

Note. Most “CrossFit” workouts are NOT HIIT. They are normally circuits (more on these later) or have other parameters of getting a certain amount of work done or maximal work in a given time frame (not knocking CrossFit).