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Sprint in Crossfit.

Although having to sprint in Crossfit is pretty rare, doing so in training can be useful. One type of adaptation to sprint training involves the enzymes involved in energy production. Multiple bouts of sprint training allow us to increase the speed at which we replenish our ATP-PC stores.

Some studies have shown that repeated bouts of sprint training increase muscular levels of CPK, which is an enzyme that catalyzes the breakdown of phosphocreatine. Other enzymes, such as phosphofructokinase, which are involved in anaerobic glycolysis, also increase as a response to sprint training. This leads to the ability to be slightly more efficient at a given velocity, and could well improve anaerobic metabolism in Crossfit athletes. Both long duration and short recovery sprints can cause adaptations to the aerobic system. A study by Dawson et. al. showed that maximal oxygen uptake (VO2 max) improved after short sprint training. As Crossfit is comprised of events requiring a decent aerobic capacity, these improvements would certainly be beneficial. An additional factor is that by improving VO2 max, athletes might be able to recover between events slightly quicker, which becomes very important in a prolonged competition such as the Crossfit Games.

A further adaptation to sprint training is that it improves the intramuscular buffering capacity, particularity if the sprints are of longer (roughly 30 second) duration. This improved buffering will enable a better resistance to fatigue in high-intensity events, such as the typical high intensity Crossfit WOD. Perhaps of even more interest to Crossfitters are the muscle adaptations to sprint training. Long term sprint based training increases the proportion of type II (fast twitch) muscle fibers an individual will have. The evidence is less clear on whether these improvements are in type IIa, IIb, IIx, or any of the other proposed type II fiber types. Nevertheless, an improvement in type II fibers will enable the athlete to produce more force, which would be useful in the strength based exercises demanded by competitive Crossfit events. Long-term sprint training has also been shown to induce muscle hypertrophy, which again is a useful adaptation for a Crossfit athlete.

Finally, sprint training improves the muscle conduction velocity, which means the motor units can fire quicker. Sprint training increases motor unit recruitment, which allows for a greater force production and may improve Olympic lifting performance. As an additional point, sprint training also likely elicits an anabolic hormone response. An increase in circulating human growth hormone and free testosterone could lead to further improvements in lean body mass and body composition that would be favorable for competitive Crossfit athletes. From the above, we can see that by using regular sprint training in their programs, Crossfit athletes could improve their performance through a variety of mechanisms.