Supplemental vitamin D enhances the recovery in peak isometric force shortly after intense exercise

Abstract

Background: Serum 25-hydroxyvitamin D (25(OH)D) concentrations associate with skeletal muscle weakness (i.e., deficit in skeletal muscle strength) after muscular injury or damage. Although supplemental vitamin D increases serum 25(OH)D concentrations, it is unknown if supplemental vitamin D enhances strength recovery after a damaging event.

Methods: Reportedly healthy and modestly active (30 minute of continuous physical activity at least 3 time/week) adult males were randomly assigned to a placebo (n = 13, age, 31(5) y; BMI, 26.9(4.2) kg/m2; serum 25(OH)D, 31.0(8.2) ng/mL) or vitamin D (cholecalciferol, 4000 IU; n = 15; age, 30(6) y; BMI, 27.6(6.0) kg/m2; serum 25(OH)D, 30.5(9.4) ng/mL) supplement. Supplements were taken daily for 35-d. After 28-d of supplementation, one randomly selected leg performed an exercise protocol (10 sets of 10 repetitive eccentric-concentric jumps on a custom horizontal plyo-press at 75% of body mass with a 20 second rest between sets) intended to induce muscle damage. During the exercise protocol, subjects were allowed to perform presses if they were unable to complete two successive jumps. Circulating chemistries (25(OH)D and alanine (ALT) and aspartate (AST) aminotransferases), single-leg peak isometric force, and muscle soreness were measured before supplementation. Circulating chemistries, single-leg peak isometric force, and muscle soreness were also measured before (immediately) and after (immediately, 1-h [blood draw only], 24-h, 48-h, 72-h, and 168-h) the damaging event.

Results: Supplemental vitamin D increased serum 25(OH)D concentrations (P < 0.05; ≈70%) and enhanced the recovery in peak isometric force after the damaging event (P < 0.05; ≈8% at 24-h). Supplemental vitamin D attenuated (P < 0.05) the immediate and delayed (48-h, 72-h, or 168-h) increase in circulating biomarkers representative of muscle damage (ALT or AST) without ameliorating muscle soreness (P > 0.05).

Conclusions: We conclude that supplemental vitamin D may serve as an attractive complementary approach to enhance the recovery of skeletal muscle strength following intense exercise in reportedly active adults with a sufficient vitamin D status prior to supplementation.

Figure 1

The % change in serum 25(OH)D concentrations from Bsl to 168-h inversely correlated with Bsl serum 25(OH)D concentrations (ng/mL) in the supplemental vitamin D group (r = -0.90, P < 0.05, solid linear regression line) but not in the placebo group (r = -0.14, P = 0.66, dashed linear regression line).

Figure 2

Plasma calcium and PTH concentrations. (A) Plasma calcium concentrations (mg/dL) were significantly (¹P < 0.05 vs. Bsl, Pre, 1-h, 24-h, 48-h, 72-h, and 168-h) increased at Post. (B) Plasma PTH concentrations (pg/mL) were significantly (²P < 0.05 vs. Pre, Post, 72-h, and 168-h) decreased at 1-h. Figure legend provided in ‘A’. Data presented as mean (SD).

Figure 3

Single-leg peak isometric force (N/kg). CON- (A) and SSC- (B) leg peak isometric forces were not significantly different between the placebo and supplemental vitamin D groups. Peak isometric force significantly decreased in the CON leg at Post, 24-h, and 48-h (¹P < 0.05 vs. Bsl and Pre). In the SSC leg, peak isometric force was significantly decreased at Post (²P < 0.05 vs. Bsl, Pre, 24-h, 48-h, 72-h, 168-h), 24-h (³P < 0.05 vs. Bsl, Pre, and 168-h), 48-h (⁴P < 0.05 vs. Bsl, Pre, 72-h, and 168-h), and 72-h (³P < 0.05 vs. Bsl, Pre, and 168-h). Peak isometric force was significantly (^#P < 0.05) different between the CON and SSC legs at Post and 48-h. Figure legend provided in ‘A’. Data presented as mean (SD).

Figure 4

Single-leg peak power output (W/kg). CON- (A) and SSC- (B) leg peak power outputs were not significantly different between the placebo and supplemental vitamin D groups. Peak power output was significantly decreased at Post (¹P < 0.05 vs. Pre, 24-h, 48-h, and 72-h) and 24-h (²P < 0.05 vs. 48-h and 72-h) in the CON leg. In the SSC leg, peak power output was significantly decreased at Post (³P < 0.05 vs. Bsl, Pre, 24-h, 48-h, 72-h, and 168-h), 24-h (⁴P < 0.05 vs. Bsl, Pre, 72-h, and 168-h), and 48-h (⁵P < 0.05 vs. Pre and 168-h). Peak power output was significantly (^#P < 0.05) different between the CON and SSC legs at Post. Figure legend provided in ‘A’. Data presented as mean (SD).

Figure 5

The recovery (%) in peak isometric force and peak power output in the SSC leg. (A) The peak isometric force % change from Post to 24-h was significantly (P < 0.05) increased in the supplemental vitamin D group compared to that in the placebo group. (B) The peak power output % change from Post to 24-h tended (P = 0.10) to be increased in the supplemental vitamin D group compared to that in the placebo group. Figure legend provided in ‘A’. Data presented as mean (SD).

Figure 6

Plasma ALT (U/L) and AST (U/L). (A) Plasma ALT increased (¹P < 0.05 vs. 24-h, 48-h, 72-h, and 168-h) in the placebo group days after the exercise protocol compared to those at Post and 1-h. Plasma ALT was significantly (²P < 0.05 vs. Bsl, Pre, 24-h, 48-h, and 72-h) decreased at Post in the supplemental vitamin D group. Supplemental vitamin D significantly (*P < 0.05) decreased ALT compared to the placebo group at 168-h. (B) Plasma AST significantly (³P < 0.05, 48-h vs. Bsl and 1-h; ⁴P < 0.05, 72-h vs. Bsl, Pre, 1-hr, and 24-hr; ⁵P < 0.05, 168-h vs. 1-h) increased in the placebo group during the days following the exercise protocol. In the supplemental vitamin D group, plasma AST was significantly increased at Post (⁶P < 0.05, vs. Bsl; ⁷P < 0.05 vs. 1-h), 48-h (⁶P < 0.05, vs. Bsl), and 168-h (⁶P < 0.05, vs. Bsl). Supplemental vitamin D significantly (^*P < 0.05) attenuated the AST increase at 48-h and 72-h compared to those in the placebo group. Figure legend provided in ‘A’. Data presented as mean (SD).

Figure 7

Perceived muscle soreness (cm). Perceived soreness in the gluteus, quadriceps, hamstrings, or calves were not significantly different between the placebo and supplemental vitamin D groups. (A-B) Gluteus soreness increased in the SSC leg at Post (¹P < 0.05 vs. 24-h and 168-h), 24-h (²P < 0.05 vs. Bsl, Pre, 72-h, and 168-h), 48-h (³P < 0.05 vs. Bsl, Pre, and 168-h), and 72-h (⁴P < 0.05 vs. 168-h). Gluteus soreness was significantly (^#P < 0.05) different between the CON and SSC leg at 24-h. (C-D) Quadriceps soreness increased in the SSC leg at Post (⁵P < 0.05 vs. Pre, 24-h, 48-h, and 168-h), 24-h (²P < 0.05 vs. Bsl, Pre, 72-h, and 168-h), 48-h (²P < 0.05 vs. Bsl, Pre, 72-h, and 168-h), and 72-h (³P < 0.05 vs. Bsl, Pre, and 168-h). Quadriceps soreness was significantly (^#P < 0.05) different between the CON and SSC leg at 24-h, 48-h, and 72-h. (E-F) Hamstring soreness increased at 24-h (³P < 0.05 vs. Bsl, Pre, and 168-h) and 48-h (³P < 0.05 vs. Bsl, Pre, and 168-h). Hamstring soreness was significantly (^#P < 0.05) different between the CON and SSC leg at 24-h. (G-H) Calf soreness increased at Post (³P < 0.05 vs. Bsl, Pre, and 168-h) and 24-h (⁶P < 0.05 vs. 72-h and 168-h). Calf soreness was not significantly different between the CON and SSC legs. Figure legend provided in ‘A’. Data presented as mean (SD).