Creatine supplementation and anterior compartment pressure during exercise in the heat in dehydrated men.

Context: Theoretically, the risk of compartment syndrome is increased during creatine monohydrate (CrM) supplementation because of intracellular fluid retention in muscle cells and the overall increased size of the muscle tissue. Whether this change in intracellular fluid is associated with an increase in anterior compartment pressure in the lower leg when subjects are under thermal stress is unknown.

Objective: To assess the influence of CrM on the resting and postexercise anterior compartment pressure of the lower leg in mildly to moderately dehydrated males exercising in the heat.

Design: Double-blind, randomized, crossover design.

Setting: Human Performance Laboratory.

Patients Or Other Participants: Eleven well-trained, non- heat-acclimated, healthy males (age = 22 +/- 2 years, height = 181.1 +/- 7 cm, mass = 78.4 +/- 4.2 kg, V(O2)max = 50.5 +/- 3.4 mL.kg(-1).min(-1)).

Intervention(s): Subjects were supplemented with 21.6 g/d of CrM or placebo for 7 days. On day 7, they performed 2 hours of submaximal exercise, alternating 30 minutes of walking with 30 minutes of cycling in the heat, resulting in approximately 2% dehydration. This was followed by an 80-minute heat tolerance test (temperature = 33.5 +/- 0.5 degrees C, humidity = 41.0 +/- 12%), which included 12 repetitions of a 3-minute walk (pace = 4.0 +/- 0.1 miles/h, intensity = 37.1 +/- 6.1% V(O2)max) alternating with a 1-minute, high-intensity run (pace = 11.8 +/- 0.4 miles/h, intensity = 115.0 +/- 5.6% V(O2)max), resulting in an additional 2% decrease in body weight.

Main Outcome Measures: Before supplementation and on day 7 of supplementation, anterior compartment pressure was measured at rest, after dehydration, and at 1, 3, 5, 10, 15, and 60 minutes after the heat tolerance test. Analysis of variance with repeated measures was calculated to compare differences within the trials and time points and to identify any interaction between trial and time.

Results: The CrM intake was associated with an increase in body weight (P < .05). A moderate effect size was noted for compartment pressures between the trials for the differences between predehydration and postdehydration (eta2 = 0.414). This effect diminished substantially by 3 minutes after the heat tolerance test. Compared with the placebo trial, the change in anterior compartment pressure from rest to dehydration was greater, as was the change from rest to 1 minute after the heat tolerance test (P < .05) during the CrM trial.

Conclusions: A 7-day loading dose of CrM increased anterior compartment pressures after dehydration and immediately after the heat tolerance tests, but the changes did not induce symptoms and the pressure changes were transient.