No Effect of Topical Application of a Commercial Magnesium Gel on Exercise Recovery in Active Individuals

Oral magnesium supplementation can reduce muscle soreness and muscle damage markers after unaccustomed exercise. However, the effectiveness of topical magnesium applications remains unclear. This randomized, double-blind, parallel-design study investigated whether a commercial magnesium gel could reduce the perception of muscle soreness and muscle damage markers following an acute bout of unaccustomed exercise. Healthy active participants (n = 35) performed a 40-min bout of downhill treadmill running. Magnesium (Mg) or placebo (Pla) gels were administered to each thigh 10 min before and immediately after exercise. Measurements were made before (Pre) and immediately (Post), 24 hr, and 48 hr after exercise. The primary outcome was muscle soreness using a 0-100 visual analog scale after a sit-to-stand maneuver. Secondary outcomes included peak isometric knee extensor strength, plasma creatine kinase, and serum interleukin-6. There were no differences between treatments on any outcome. Compared with Pre (Mg: 4 ± 5, Pla: 4 ± 5 a.u.), muscle soreness was higher post (Mg: 28 ± 20, Pla: 21 ± 14) and after 24 hr (Mg: 43 ± 27, Pla: 41 ± 26) and 48 hr (Mg: 42 ± 31, Pla: 32 ± 23) (all main effects, p < .0001). Interleukin-6 was higher Post (Mg: 1.8 ± 0.7, Pla: 1.6 ± 0.7 pg/ml) versus Pre (Mg: 1.1 ± 0.8, Pla: 1.1 ± 0.6; main effect, p = .006), and creatine kinase was higher Post (Mg: 111 ± 57, Pla: 121 ± 44 U/L), 24 hr (Mg: 216 ± 113, Pla: 228 ± 97), and 48 hr (Mg: 136 ± 45, Pla: 179 ± 85) versus Pre (Mg: 93 ± 54, Pla: 91 ± 30; all main effects, p < .001). Knee extensor strength was reduced after exercise (main effect, p = .04). The Mg gel did not reduce muscle soreness or muscle damage markers after unaccustomed exercise compared with Pla. The dose (0.53 mg/ml) or application protocol may have been insufficient to elicit a meaningful effect.