Vitamin D3 supplementation does not enhance the effects of resistance training in older adults

Abstract

Background: Lifestyle therapy with resistance training is a potent measure to counteract age-related loss in muscle strength and mass. Unfortunately, many individuals fail to respond in the expected manner. This phenomenon is particularly common among older adults and those with chronic diseases (e.g. chronic obstructive pulmonary disease, COPD) and may involve endocrine variables such as vitamin D. At present, the effects of vitamin D supplementation on responses to resistance training remain largely unexplored.

Methods: Ninety-five male and female participants (healthy, n = 71; COPD, n = 24; age 68 ± 5 years) were randomly assigned to receive either vitamin D₃ or placebo supplementation for 28 weeks in a double-blinded manner (latitude 61°N, September-May). Seventy-eight participants completed the RCT, which was initiated by 12 weeks of supplementation-only (two weeks with 10 000 IU/day, followed by 2000 IU/day), followed by 13 weeks of combined supplementation (2000 IU/day) and supervised whole-body resistance training (twice weekly), interspersed with testing and measurements. Outcome measures included multiple assessments of muscle strength (n_variables = 7), endurance performance (n = 6), and muscle mass (n = 3, legs, primary), as well as muscle quality (legs), muscle biology (m. vastus lateralis; muscle fibre characteristics, transcriptome), and health-related variables (e.g. visceral fat mass and blood lipid profile). For main outcome domains such as muscle strength and muscle mass, weighted combined factors were calculated from the range of singular assessments.

Results: Overall, 13 weeks of resistance training increased muscle strength (13% ± 8%), muscle mass (9% ± 8%), and endurance performance (one-legged, 23% ± 15%; whole-body, 8% ± 7%), assessed as weighted combined factors, and were associated with changes in health variables (e.g. visceral fat, -6% ± 21%; [LDL]_serum , -4% ± 14%) and muscle tissue characteristics such as fibre type proportions (e.g. IIX, -3% points), myonuclei per fibre (30% ± 65%), total RNA/rRNA abundances (15%/6-19%), and transcriptome profiles (e.g. 312 differentially expressed genes). Vitamin D₃ supplementation did not affect training-associated changes for any of the main outcome domains, despite robust increases in [25(OH)D]_serum (∆49% vs. placebo). No conditional effects were observed for COPD vs. healthy or pre-RCT [25(OH)D]_serum . In secondary analyses, vitamin D₃ affected expression of gene sets involved in vascular functions in muscle tissue and strength gains in participants with high fat mass, which advocates further study.

Conclusions: Vitamin D₃ supplementation did not affect muscular responses to resistance training in older adults with or without COPD.

Keywords: Cholecalciferol; Muscle plasticity; Strength training.

Figure 1

CONSORT flow chart of the study.

Figure 2

Schematic overview of the study protocol. Pre‐defined main time frames (baseline and end time points) for specific outcome measures (the color lines represents the measurement marked with the same color at the top of the figure; (A), vitamin D‐status (25‐hydroxyvitamin D levels, (B) and 1,25 dihydroxyvitamin D levels (C) during the RCT, training volume during the resistance training intervention (D), and perceived exertion (Borg RPE, 6–20) reported after training sessions (E). The training volume was calculated as average increase in volume (kg · repetitions) in leg press and knee extension from the first week of training. STR, maximal strength test; Musc.perf., test of muscular performance; 1‐LC, one‐legged cycling test; Func., test of functional capacity (6‐min step test and 1‐min sit‐to‐stand test); US, ultrasound measures of muscle thickness; DXA, Dual‐energy X‐ray Absorptiometry; V̇O_{2 max}, maximal oxygen consumption; IU, international units; RT, resistance training; 25(OH)D, 25‐hydroxyvitamin D. In ( B ), statistical differences between time points and supplementation arms are denoted by letters: different letter indicates P < 0.05, that is, all time point measures denoted with the same letter are statistically similar (P > 0.05). Data for 25(OH)D and training volume are presented as means with 95% confidence intervals.

Figure 3

Representative immunohistochemistry images of (A) myosin heavy chain I (green) and cell membrane (red), (B) myonuclei (blue) and cell membrane (dystrophin, red), and (C) myosin heavy chain I (blue), IIA (green), IIX (red), and IIA/IIX hybrids (orange). Images in (A) and (B) are from the same tissue cross‐section: triple‐staining myosin heavy chain I, dystrophin and cell nuclei.

Figure 4

Primary outcome objectives of the study; effects of combined vitamin D₃ supplementation and resistance training on changes in muscle fibre cross‐sectional area (A, B) and fibre type proportions (C–E) in older adults. Alpha level at P < 0.05. Data are presented as means with 95% confidence intervals.

Figure 5

Effects of 12 weeks of vitamin D₃ supplementation‐only on whole‐genome transcriptome profiles in m. vastus lateralis of older adults. After 12 weeks of supplementation‐only, numerous genes were differentially expressed between the vitamin D₃ and the placebo arm (A); ∆, pre‐introduction to resistance training/pre‐RCT). Gene ontology (GO) enrichment analyses showed that these genes were primarily related to mitochondrial function and cell cortex/cell‐substrate junction (B); positive/negative GSEA‐normalized enrichment scores indicates higher/lower expression of gene sets in the vitamin D₃ arm compared with the placebo arm). The seven differentially expressed gene sets were clustered into two distinct groups of genes (C).

Figure 6

Effects of combined vitamin D₃ supplementation and resistance training on maximal muscle strength in older adults. Changes in muscle strength from baseline (after three weeks of introduction to resistance training) to post‐RCT (A), and differences in changes between vitamin D₃ and placebo arms (B). KE, one‐legged knee extension; LP, one‐legged leg press; CP, chest press; maximal torque measured using one‐legged knee extension at three velocities; 60, 180, and 240° per second; #, significant difference between vitamin D₃ and placebo arms; combined strength factor, weighted combined strength factor of unilateral strength measures (one‐repetition maximum in KE and LP, and KE torque at 60, 180, and 240° per second). Alpha level at P < 0.05. Data are presented as means with 95% confidence intervals.

Figure 7

Effects of combined vitamin D₃ supplementation and resistance training on lower‐limb muscle mass in older adults. Changes in lower‐limb muscle mass from baseline (before introduction to resistance training) to post‐RCT (A), and differences in changes between vitamin D₃ and placebo arms (B). CSA, cross‐sectional area (also presented in Figure 4); RF, m. rectus femoris; VL, m. vastus lateralis; LM per leg, leg lean mass per leg; #, significant difference between vitamin D₃ and placebo arms; combined muscle mass factor, weighted combined muscle mass factor including fibre cross‐sectional area (type I and type II), muscle thickness (RF and VL) and LM per leg; muscle quality, muscle strength factor/muscle mass factor. Alpha level at P < 0.05. Data are presented as means with 95% confidence intervals.

Figure 8

Effects of combined vitamin D₃ supplementation and resistance training on one‐legged and whole‐body endurance performance in older adults. Changes in endurance performance from baseline (before introduction to resistance training) to post‐RCT (A), and differences in changes between vitamin D₃ and placebo arms (B). 1KE, repetitions to failure in one‐legged knee extension (50% of pre‐intervention 1RM); CP, repetitions to failure in chest press (50% of pre‐intervention 1RM); W_max, maximal power output; 6‐min step test, maximal number of steps achieved during 6 min; Sit‐to‐stand, maximal number of sit‐to‐stands achieved during 1 min; combined 1‐leg endurance performance factor, weighted combined one‐legged endurance factor including 1KE muscular performance and one‐legged cycling W_max; weighted combined whole‐body endurance factor including W_max bicycling, 6‐min step test and sit‐to‐stand test. Alpha level at P < 0.05. Data are presented as means with 95% confidence intervals.

Figure 9

Effects of combined vitamin D₃ supplementation and resistance training on muscle fibre type proportions and myonuclei per fibre in m. vastus lateralis of older adults. Muscle fibre type proportions (A–F) at baseline (before introduction to resistance training) and post‐RCT measured using immunohistochemistry (A–C) and qPCR (gene family profiling (GeneFam)‐normalized myosin heavy chain mRNA expression, (D–F), and changes in myonuclei count per type I and type II fibre from baseline to post‐RCT (G). Significant changes were observed for fibre type IIA and IIX using both methods (significant increase and decrease, respectively; P < 0.05). For fibre type I, an increased expression was present using qPCR (P < 0.05), but no change was observed for immunohistochemistry (P = 0.322). P‐values denotes the statistical difference between the supplementation arms. RT, resistance training. Data are presented as means with 95% confidence intervals.

Figure 10

Effects of combined vitamin D₃ supplementation and resistance training on total RNA abundances and rRNA expression in m. vastus lateralis of older adults. Total RNA (A), 18 s rRNA (B), 28 s rRNA (C), 5.8 s rRNA (D), 5 s rRNA (E), and 45 s pre‐rRNA (F) abundances at baseline (before introduction to resistance training) and post‐RCT. Significant increases from baseline–post‐introduction to resistance training were present for all variables (P < 0.05). From baseline–post‐RCT significant increases were present for all variables (P < 0.05), with the exception of 5.8 s rRNA (P = 0.722) and 5 s rRNA (P = 0.940). RT, resistance training. P‐values denotes the statistical difference between the supplementation arms. Alpha level at P < 0.05. Data are presented relative to amounts of tissue weight. Data are presented as means with 95% confidence intervals.

Figure 11

Effects of 3.5/13 weeks of resistance training‐only (A–C) and 3.5/13 weeks of combined vitamin D₃ supplementation and resistance training (D–G) on mRNA transcriptome profiles in m. vastus lateralis of older adults. Resistance training‐only led to robust changes in gene expression at both 3.5 weeks (A; post‐intro resistance training – pre‐intro resistance training) and 13 weeks (B; post‐RCT – pre‐intro resistance training), including increased expression of collagen type IV α1 and α2 genes (COL4A1 and COL4A2, respectively) and decreased expression of the myosin heavy chain IIX gene (MYH1). The three most enriched gene sets with increased and decreased expression, in addition to the ‘blood vessel morphogenesis’ gene set are shown in C (light blue, 3.5 weeks; dark blue, 13 weeks; according to the GSEA enrichment score). Combined vitamin D₃ supplementation and resistance training did not lead to differential changes in expression for a singular gene compared with placebo at neither 3.5 weeks (D; ∆, post‐introduction to resistance training ‐ pre‐introduction to resistance training) nor 13 weeks of resistance training (E; ∆, post‐RCT ‐ pre‐introduction to resistance training; orange dots/genes denotes leading edge genes from the ‘blood vessel morphogenesis’ GO gene set, that is, the most highly enriched gene set between supplementation arms after 13 weeks of resistance training). GO enrichment analyses of differentially regulated gene sets between the vitamin D₃ and the placebo arms following 3.5 weeks (left panel, F) and 13 weeks of resistance training (right panel, F; positive/negative GSEA‐normalized enrichment scores indicates higher/lower expression of gene sets in the vitamin D₃ arm compared with the placebo arm). (G) Timeline for the 10 most affected genes between vitamin D₃ and placebo arms belonging to the ‘blood vessel morphogenesis’ GO gene set. RT, resistance training; Consensus, when both the non‐directional rank‐based enrichment test and the directional gene‐set enrichment analysis (GSEA) turned out significant. In Figure 11 C,F, circle sizes of gene sets are relative to P‐values, i.e. larger circles indicate lower P‐values (see Supporting Information, Tables S5 – S10 for exact P‐values).