Abstract
Converting from an omnivorous (OMNI) diet to a lacto-ovo-vegetarian (LOV) diet has been associated with a decrease in muscle creatine content as a result of the elimination of exogenous creatine intake. Muscle creatine and phosphocreatine are vital in sustaining intense and rapid muscle contractions during exercise. It is unknown if the transition to LOV diet leads to negative impacts on muscle performance due to the reduction of muscle creatine content. PURPOSE: To investigate the effects of creatine supplementation during a 21-day LOV intervention on muscle performance in young males. METHODS: Twenty-eight males (22.2 ± 2.5 yrs old) switched from an OMNI to a LOV diet for 21 days. Participants were assigned into one of two groups: Placebo (Pl; n=15) or Creatine (Cr, 2g; n=13) for 21 days. Muscle strength was evaluated for the upper body by performing 1-repetition maximum (1-RM) tests for the chest press (Smith Machine) and for the lower body by performing maximal voluntary contraction (MVC) of the quadriceps (QUAD) (BiodexTM) before initiation of LOV diet and 21 days after initiation of LOV diet. Muscle endurance for the QUAD was evaluated with two consecutive bouts (bouts 1 and 2) of a fatigue index (FI) test with one minute rest (BiodexTM) at the same time points. Dual-energy-X-ray absorptiometry (DXA) was used to measure body composition at the same time points. Blood samples were collected at same time points. Dietary records were obtained for both OMNI and LOVdiets. RESULTS: There was a group x time interaction (p< 0.05) in FI bout 2 for peak torque, indicating that the QUAD strength for Cr group was changed from 111.62 ± 19.53 (pre) to 121.69 ± 21.5 Newton meters (Nm, post) while that of the Pl group was changed from 138.2 ± 33.08 (pre) to 130.73 ± 32.05 Nm (post) after 21-day LOV intervention. Interestingly, there was a group x time interaction (p=0.05) in FI for percent torque decline during bout 2, indicating that the Cr group changed from -60.75 ± 2.13 (pre) to -61.99 ± 2.53% (post) while Pl group changed from -64.3 ± 2.83 (pre) to -58.64 ± 3.68% (post) after 21-day LOV intervention. There was a group x time interaction (p<0.05) in isometric knee extensions for peak force, indicating that the QUAD strength for Cr group was changed from 204.08 ± 47.05 (pre), to 187.0 ± 43.57 (mid), to 182.0 ± 50.37 Newtons (N,post) while that of the Pl group was changed from 204.87 ± 50.74 (pre), to 211.47 ± 45.36 (mid), to 211.0 ± 53.37 N (post). There was no significant change in body weight, lean body mass, fat mass, total cholesterol, HDL cholesterol, MVC isokinetic extensions at 60, 180, and 300 degrees/second in QUAD, or 1-RM chest press. There was a time effect (p<0.05) indicating a significant decline in protein intake for both groups. CONCLUSIONS: Our findings suggest that 21 days of LOV diet in young males who were previously omnivorous did not have any negative impacts on muscle performance. Daily creatine supplementation (2g/d) during 21-day LOV diet intervention appears to maintain muscle strength during the second bout of consecutive fatigability tests.
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