High intensity interval training vs high volume training on improving repeated sprint ability among u17 professional soccer players a comparative study.

Soccer is a high-intensity intermittent sport involving actions like sprints, jumps, and changes of direction, interspersed with low-intensity recovery. Over the past 15 years, match intensity has risen, with sprint distances increasing by ~50% and high-speed running by ~29%. Players cover 9–12 km per match, with 8–12% at high intensity, performing 17–81 sprints per game—most under 20 m and lasting 2–4 seconds.

Repeated-sprint training is low-volume and short in duration, typically lasting 10–20 min per session, but due to the maximal intensity at which it is performed, it can generate adaptive events that ultimately result in the capacity for enhanced performance.

Fartlek is Swedish word which means "speed play". Fartlek training “is simply defined as periods of fast running intermixed with periods of slower running. It differs from traditional interval training in that it is unstructured intensity and speed varies, as the athlete wishes.