Abstract
PURPOSE: Vitamin K2 supplementation has emerged as a strategy to enhance recovery and modulate postexercise physiological responses. This study aimed to assess the effects of vitamin K2 on recovery from muscle-damaging exercise in young and older adults. METHODS: Healthy young (18-40 yr) and older (65+ yr) adults were randomly assigned to either vitamin K2 (menaquinone-7, MK-7, 240 μg/d) or placebo (cellulose) for 12 wk in this double-blind randomized controlled trial. Before and after supplementation, knee extensor maximal torque, functional ability, muscle soreness, and systemic blood markers of muscle damage and inflammation were measured before (0 h) and 3, 24, 48, and 72-h postexercise. Data were analyzed using regression and mixed models. RESULTS: Seventy-one participants (35 young and 36 older) completed the study, with 12 wk of vitamin K2 supplementation increasing circulating MK-7 levels (P-value <0.001). There were no supplement × time effects for any variables. Significant supplement × time × older age interaction effects were noted for electromechanical delay (EMD) (P-value = 0.03), electromyography root mean square (RMS) (P-value = 0.01), interleukin-6 (IL-6) concentrations (P-value <0.001), and creatine kinase (CK) levels (P-value = 0.02). In older adults, after 12 wk, EMD appeared lower at all time points and RMS higher postexercise in the vitamin K2 group. No clear pattern in IL-6 or CK was observed, but at 72-h postexercise CK was lower in older adults in the vitamin K2 group. CONCLUSIONS: Vitamin K2 supplementation had no effect on muscle strength, physical function, muscle soreness, or inflammatory responses in the recovery period after a bout of resistance exercise. Effects of supplementation were observed on EMD, RMS, IL-6, and CK by age and warrant further investigation.