Influence of vitamin D mushroom powder supplementation on exercise-induced muscle damage in vitamin D insufficient high school athletes Vitamin D3 supplementation using an oral spray solution resolves deficiency but has no effect on VO2 max in Gaelic footballers: results from a randomised, double-blind, placebo-controlled trial Acute Effects of Vitamin D3 Supplementation on Muscle Strength in Judoka Athletes: A Randomized Placebo-Controlled, Double-Blind Trial The effects of vitamin D3 supplementation on serum total 25[OH]D concentration and physical performance: a randomised dose–response study Vitamin D supplementation during rehabilitation in COPD: a secondary analysis of a randomized trial A randomized study on the effect of vitamin D₃ supplementation on skeletal muscle morphology and vitamin D receptor concentration in older women. Does quercetin and vitamin C improve exercise performance, muscle damage, and body composition in male athletes? Relationships among nutritional status and skeletal and respiratory muscle function in cystic fibrosis: does early dietary supplementation make a difference? Improving the vitamin D status of vitamin D deficient adults is associated with improved mitochondrial oxidative function in skeletal muscle. Skeletal muscle strength in young Asian Indian females after vitamin D and calcium supplementation: a double-blind randomized controlled clinical trial. Whey protein, amino acids, and vitamin D supplementation with physical activity increases fat-free mass and strength, functionality, and quality of life and decreases inflammation in sarcopenic elderly. Low-Dose Vitamin D Prevents Muscular Atrophy and Reduces Falls and Hip Fractures in Women after Stroke: A Randomized Controlled Trial Correcting Vitamin D Insufficiency Improves Some But Not All Aspects of Physical Performance During Winter Training in Taekwondo Athletes. Supplementation with vitamins C and E inhibits the release of interleukin-6 from contracting human skeletal muscle. Vitamin D2 Supplementation Amplifies Eccentric Exercise-Induced Muscle Damage in NASCAR Pit Crew Athletes
Abstract Incidence of vitamin D deficiency is increasing worldwide . The purpose of this study was to determine if supplementation with vitamin D2 from Portobello mushroom powder would enhance skeletal muscle function and attenuate exercise-induced muscle damage in low vitamin D status high school athletes . Participants were r and omised to Portobello mushroom powder ( 600 IU/d vitamin D2 ) or placebo for 6 weeks . Participants then completed a 1.5-h exercise session design ed to induce skeletal muscle damage . Blood sample s and measures of skeletal muscle function were taken pre-supplementation , post-supplementation/pre-exercise and post-exercise . Six weeks supplementation with vitamin D2 increased serum 25(OH)D2 by 9.9-fold and decreased serum 25(OH)D3 by 28 % . Changes in skeletal muscle function and circulating markers of skeletal muscle damage did not differ between groups . In conclusion , 600 IU/d vitamin D2 increased 25(OH)D2 with a concomitant decrease in 25(OD)D3 , with no effect on muscular function or exercise-induced muscle damage in high school athletes Purpose Vitamin D inadequacy is a global health concern in athletes as well as the general population . Whilst the role of vitamin D in skeletal health is well defined , there remains uncertainty over whether vitamin D supplementation has an added benefit beyond bone health . Methods This r and omised placebo-controlled trial in healthy male and female Gaelic footballers ( n = 42 ) investigated the effect of vitamin D3 supplementation [ 3000 IU ( 75 µg ) daily for 12 weeks , via an oral spray solution ] on VO2 max which was the primary outcome measure . Secondary outcomes included skeletal muscle and lung function . Results Supplementation significantly increased total 25-hydroxyvitamin D concentrations compared to the placebo group ( mean ± SD change from baseline , 36.31 ± 32.34 vs. 6.11 ± 23.93 nmol/L , respectively ; P = 0.006 ) . At baseline , 50 and 22 % of footballers presented with vitamin D insufficiency ( 31–49 nmol/L ) and deficiency ( < 30 nmol/L ) , respectively . Total 25-hydroxyvitamin D concentration did not significantly correlate with any measure of physical performance . Analysis of covariance ( ANCOVA ) models demonstrated that vitamin D supplementation over 12 weeks had no significant effect on VO2 max ( P = 0.375 ) , vertical jump height ( P = 0.797 ) , left and right h and grip strength ( P = 0.146 and P = 0.266 , respectively ) , forced vital capacity ( P = 0.573 ) or forced expiratory volume at 1 s ( P = 0.665 ) , after adjusting for confounders . The high prevalence of vitamin D inadequacy observed in this cohort of collegiate Gaelic footballers supports the need for vitamin D supplementation during wintertime to avoid being at risk of poor bone health . Conclusions Twelve-week daily supplementation with 3000 IU ( 75 µg ) vitamin D3 successfully resolved deficiency but did not have any significant effect on VO2 max , skeletal muscle or lung function Objective : Indoor athletes have been shown to be prone to vitamin D3 deficiency . The aim of the study was to examine the acute effects of vitamin D supplementation on muscle function using isokinetic dynamometry . Design : R and omized placebo-controlled , double-blind study . Setting : Institutional . Participants : Adult male white national level judoka athletes ( n = 22 ) who were involved in full-time training . Exclusion criteria were vitamin supplementation , overseas travel to sunny climes , and /or an injury incurred during the last 3 months before testing . Interventions : Subjects were r and omly allocated to the treatment ( 150 000IU vitamin D3 ) or placebo and given blinded supplements by an independent research er . Participants were tested twice , 8 days apart , on a Monday morning before the start of judo training and after 2 days of rest . A 5 to 7 mL of blood sample was collected followed by isokinetic concentric quadriceps and hamstring muscle function assessment s on the right leg at 30 and 200 ° ·s−1 . Main Outcome Measures : Repeated- measures analysis of variance was used to analyze isokinetic muscle force and serum 25(OH)D3 . Regression to the mean was used to examine changes in 25(OH)D3 levels over the study period . Results : The treatment group demonstrated a significant increase in serum 25(OH)D levels ( 34 % , P ⩽ 0.001 ) and muscle strength ( 13 % , P = 0.01 ) between days 1 and 8 . No significant differences were found for the placebo group for the same period . Conclusions : A single bolus of 150 000IU vitamin D3 had a significant positive effect on serum 25(OH)D levels and muscle function in vitamin D insufficient elite indoor athletes . Clinical Relevance : Serum 25(OH)D3 levels of indoor athletes should be monitored throughout the year and especially during winter months . Beneficial responses , in muscle strength and serum 25(OH)D3 , to 1 dose of vitamin D3 supplementation can be observed within 1 week of ingestion . Muscle strength is linked to serum 25(OH)D levels Background Vitamin D deficiency is common in the general public and athletic population s and may impair skeletal muscle function . We therefore assessed the effects of vitamin D3 supplementation on serum 25[OH]D concentrations and physical performance . Methods 30 club-level athletes were block r and omised ( using baseline 25[OH]D concentrations ) into one of three groups receiving either a placebo ( PLB ) , 20 000 or 40 000 IU/week oral vitamin D3 for 12 weeks . Serum 25[OH]D and muscle function ( 1-RM bench press and leg press and vertical jump height ) were measured presupplementation , 6 and 12 weeks postsupplementation . Vitamin D deficiency was defined in accordance with the US Institute of Medicine guideline ( < 50 nmol/l ) . Results 57 % of the subject population were vitamin D deficient at baseline ( mean±SD value 51±24 nmol/l ) . Following 6 and 12 weeks supplementation with 20 000 IU ( 79±14 and 85±10 nmol/l , respectively ) or 40 000 IU vitamin D3 ( 98±14 and 91±24 nmol/l , respectively ) , serum vitamin D concentrations increased in all participants , with every individual achieving concentrations greater than 50 nmol/l . In contrast , vitamin D concentration in the PLB group decreased at 6 and 12 weeks ( 37±18 and 41±22 nmol/l , respectively ) . Increasing serum 25[OH]D had no significant effect on any physical performance parameter ( p>0.05 ) . Conclusions Both 20 000 and 40 000 IU vitamin D3 supplementation over a 6-week period elevates serum 25[OH]D concentrations above 50 nmol/l , but neither dose given for 12 weeks improved our chosen measures of physical performance Rationale Pulmonary rehabilitation is an important treatment for patients with Chronic Obstructive Pulmonary Disease , who are often vitamin D deficient . As vitamin D status is linked to skeletal muscle function , we aim ed to explore if high dose vitamin D supplementation can improve the outcomes of rehabilitation in Chronic Obstructive Pulmonary Disease . Material and methods This study is a post-hoc subgroup analysis of a larger r and omized trial comparing a monthly dose of 100.000 IU of vitamin D with placebo to reduce exacerbations . 50 Subjects who followed a rehabilitation program during the trial are included in this analysis . We report changes from baseline in muscle strength and exercise performance between both study arms after 3 months of rehabilitation . Results Vitamin D intervention result ed in significantly higher median vitamin D levels compared to placebo ( 51 [ 44 - 62 ] ng/ml vs 15 [ 13 - 30 ] ng/ml ; p < 0.001 ) . Patients receiving vitamin D had significantly larger improvements in inspiratory muscle strength ( -11±12 cmH2O vs 0±14 cmH2O ; p = 0.004 ) and maximal oxygen uptake ( 110±211 ml/min vs -20±187 ml/min ; p = 0.029 ) . Improvements in quadriceps strength ( 15±16 Nm ) or six minutes walking distance ( 40±55 meter ) were not significantly different from the effects in the placebo group ( 7±19 Nm and 11±74 meter ; p>0.050 ) . Conclusion High dose vitamin D supplementation during rehabilitation may have mild additional benefits to training CONTEXT Studies examining whether vitamin D supplementation increases muscle mass or muscle-specific vitamin D receptor ( VDR ) concentration are lacking . OBJECTIVE Our objective was to determine whether vitamin D₃ 4000 IU/d alters muscle fiber cross-sectional area ( FCSA ) and intramyonuclear VDR concentration over 4 months . DESIGN AND SETTING This was a r and omized , double-blind , placebo-controlled study in a single center . PARTICIPANTS Participants were 21 mobility-limited women ( aged ≥ 65 years ) with serum 25-hydroxyvitamin D ( 25OHD ) levels of 22.5 to 60 nmol/L. MAIN OUTCOME MEASURES Baseline and 4-month FCSA and intramyonuclear VDR were measured from vastus lateralis muscle cross-sections probed for muscle fiber type ( I/IIa/IIx ) and VDR using immunofluorescence . RESULTS At baseline , mean ( ±SD ) age was 78 ± 5 years ; body mass index was 27 ± 5 kg/m² , 25OHD was 46.3 ± 9.5 nmol/L , and  a short physical performance battery score was 7.95 ± 1.57 out of 12 . At 4 months , 25OHD level was 52.5 ± 17.1 ( placebo ) vs 80.0 ± 11.5 nmol/L ( vitamin D [ VD ] ; P < .01 ) , and change in 25OHD level was strongly associated with percent change in intramyonuclear VDR concentration-independent of group ( r = 0.87 , P < .001 ) . By treatment group , percent change in intramyonuclear VDR concentration was 7.8 % ± 18.2 % ( placebo ) vs 29.7 % ± 11.7 % ( VD ; P = .03 ) with a more pronounced group difference in type II vs I fibers . Percent change in total ( type I/II ) FCSA was -7.4 % ± 18.9 % ( placebo ) vs 10.6 % ± 20.0 % ( VD ; P = .048 ) . CONCLUSION Vitamin D₃ supplementation  increased intramyonuclear VDR concentration by 30 % and increased muscle fiber size by 10 % in older , mobility-limited , vitamin D-insufficient women . Further work is needed to determine whether the observed effect of vitamin D on fiber size is mediated by the VDR and to identify which signaling pathways are involved Background : Quercetin is a bioflavonoid occurs in many food items . Some previous studies on quercetin showed the inconsistent results on exercise performance and muscle damage in athletes . The aim of this study was to determine the effects of 8 weeks of quercetin supplementation on exercise performance and muscle damage indices in student athletes . Methods : This placebo-controlled , double-blind clinical trial was conducted on 60 male students for 8 weeks . The subjects were r and omly assigned to one of the four groups : a ) quercetin ( 500 mg/day quercetin + 200 mg/day placebo ) , b ) quercetin+ vitamin C ( 500 mg/day quercetin + 200 mg/day vitamin C ) , vitamin C ( 500 mg/day placebo + 200 mg/day vitamin C ) , and placebo ( 500 mg/day placebo + 200 mg/day placebo ) . Time to exhaustion ( TTE ) for measuring performance , aspartate transaminase ( AST ) , and creatine kinase ( CK ) for measuring muscle damage and body fat percent ( BFP ) were measured before and after intervention . Results : CK levels reduced in group 1 significantly ( P=0.045 ) and BFP reduced in group 1 , 3 , and 4 , significantly , too ( P=0.018 , P=0.013 , and P=0.043 , respectively ) . Whereas statistically significant changes between groups were not observed for TTE , AST , CK , and BFP after 8 weeks of intervention . Conclusions : Supplementation with quercetin and vitamin C for 8 weeks did not improve exercise performance but reduced muscle damage and body fat percent in healthy subjects Relationships among nutritional status and skeletal and respiratory muscle function were examined in 16 children with cystic fibrosis ( CF ) and mild lung disease ( FEV1 95 + /- 16 % predicted ) . Subjects were r and omly assigned to receive ( or not ) noninvasive nutritional supplementation at 25 % of normal energy recommendations for 6 mo . Skeletal muscle strength and power were similar to those of healthy children as were respiratory muscle strength and endurance . Stepwise-regression analysis indicated that changes in skeletal muscle strength and energy intake correlated significantly with growth [ weight ( kg ) = 1.90 - 0.60 ( Tanner Stage ) + 0.49 ( maximum voluntary strength ( Nm ) + 0.03 ( energy intake , % RNI ) , r = 0.76 , P < 0.05 ] , though body composition , protein biochemistry , muscle power , respiratory muscle strength , and use of dietary supplements did not . Thus , changes in skeletal muscle strength may be a functional index of changes in nutritional status in CF . Dietary supplementation per se was not associated with functional improvement OBJECTIVE Suboptimal mitochondrial function has been implicated in several disorders in which fatigue is a prominent feature . Vitamin D deficiency is a well-recognized cause of fatigue and myopathy . The aim of this study was to examine the effects of cholecalciferol therapy on skeletal mitochondrial oxidative function in symptomatic , vitamin D-deficient individuals . DESIGN This longitudinal study assessed mitochondrial oxidative phosphorylation in the gastrosoleus compartment using phosphorus-31 magnetic resonance spectroscopy measurements of phosphocreatine recovery kinetics in 12 symptomatic , severely vitamin D-deficient subjects before and after treatment with cholecalciferol .  All subjects had serum assays before and after cholecalciferol therapy to document serum 25-hydroxyvitamin D ( 25OHD ) and bone profiles . Fifteen healthy controls also underwent (31)P-magnetic resonance spectroscopy and serum 25OHD assessment . RESULTS The phosphocreatine recovery half-time ( τ1/2PCr ) was significantly reduced after cholecalciferol therapy in the subjects indicating an improvement in maximal oxidative phosphorylation ( 34.44 ± 8.18 sec to 27.84 ± 9.54 sec , P < .001 ) . This was associated with an improvement in mean serum 25OHD levels ( 8.8 ± 4.2 nmol/L to 113.8 ± 51.5 nmol/L , P < .001 ) . There was no difference in phosphate metabolites at rest . A linear regression model showed that decreasing serum 25OHD levels was associated with increasing τ1/2PCr ( r = -0.41 , P = .009 ) . All patients reported an improvement in fatigue  after cholecalciferol therapy . CONCLUSIONS Cholecalciferol therapy augments muscle mitochondrial maximal oxidative phosphorylation after exercise in symptomatic , vitamin D-deficient individuals . This finding suggests that changes in mitochondrial oxidative phosphorylation in skeletal muscle could at least be partly responsible for the fatigue experienced by these patients . For the first time , we demonstrate a link between vitamin D and the mitochondria in human skeletal muscle CONTEXT R and omized control trials ( RCT ) of the effect of vitamin D/calcium supplementation on skeletal muscle strength have not shown promising effect in the elderly . OBJECTIVE Our objective was to assess the effect of vitamin D and /or calcium on muscle strength in young adults with vitamin D deficiency . DESIGN AND SETTING We conducted a RCT using a factorial design at a tertiary-care center from September 2010 to April 2011 . SUBJECTS A total of 173 healthy females with mean age , body mass index , and 25-hydroxyvitamin D [ 25(OH)D ] of 21.7 ± 4.4 yr , 20.8 ± 2.96 kg/m(2 ) , and 9.3 ± 3.37 ng/ml , respectively , were block r and omized to 1 ) double placebo , 2 ) calcium/placebo , 3 ) cholecalciferol/placebo , and 4 ) cholecalciferol/calcium for 6 months . Cholecalciferol was given at 60,000 IU/wk for 8 wk followed by 60,000 IU/fortnight . Elemental calcium was given in doses of 500 mg twice per day for 6 months . METHODS Assessment included h and grip ( primary outcome ) and pinch grip strength , distance walked in 6 min , dyspnea score , quality of life by Short Form ( 36 ) Health Survey ( SP-36 ) , serum 25(OH)D , 1,25-dihydroxyvitamin D , and intact PTH . RESULTS The serum 25(OH)D increased significantly to 29.9 ± 8.35 and 27.0 ± 9.54 ng/ml in two groups on cholecalciferol . The mean h and grip strength ( 19.4 ± 3.92 , 21.1 ± 3.31 , 20.6 ± 3.92 , and 20.1 ± 4.00 kg ) and its increase from baseline ( 0.3 ± 2.25 , 0.3 ± 2.64 , -0.3 ± 2.41 , and 0.6 ± 2.30 kg ) were comparable in four groups at 6 months . Quality of life , urinary calcium/creatinine ratio , and adverse effects were also comparable in groups . CONCLUSION Oral cholecalciferol/calcium supplementation in the dose/schedule used is effective and safe in increasing and maintaining serum 25(OH)D. However , this does not lead to improved skeletal muscle strength in young females BACKGROUND Interventions to attenuate the adverse effects of age-related loss of skeletal muscle and function include increased physical activity and nutritional supplementation . OBJECTIVE This study tested the hypothesis that nutritional supplementation with whey protein ( 22 g ) , essential amino acids ( 10.9 g , including 4 g leucine ) , and vitamin D [ 2.5 μg ( 100 IU ) ] concurrent with regular , controlled physical activity would increase fat-free mass , strength , physical function , and quality of life , and reduce the risk of malnutrition in sarcopenic elderly persons . DESIGN A total of 130 sarcopenic elderly people ( 53 men and 77 women ; mean age : 80.3 y ) participated in a 12-wk r and omized , double-blind , placebo-controlled  supplementation trial . All participants concurrently took part in a controlled physical activity program . We examined body composition with dual-energy X-ray absorptiometry , muscle strength with a h and grip dynamometer , and blood biochemical indexes of nutritional and health status , and evaluated global nutritional status , physical function , and quality of life before and after the 12 wk of intervention . RESULTS Compared with physical activity and placebo , supplementation plus physical activity  increased fat-free mass ( 1.7-kg gain , P < 0.001 ) , relative skeletal muscle mass ( P = 0.009 ) , and roid distribution of fat ( P = 0.021 ) , h and grip strength ( P = 0.001 ) , st and ardized summary scores for physical components ( P = 0.030 ) , activities of daily living ( P = 0.001 ) , mini nutritional assessment ( P = 0.003 ) , and insulin-like growth factor I ( P = 0.002 ) , and lowered C-reactive protein ( P = 0.038 ) . CONCLUSION Supplementation with whey protein , essential amino acids , and vitamin D , in conjunction with age-appropriate exercise , not only boosts fat-free mass and strength but also enhances other aspects that contribute to well-being in sarcopenic elderly . This trial was registered at clinical trials.gov as NCT02402608 OBJECTIVE Vitamin D supplementation is suggested to reduce the risk of falls among ambulatory or institutionalized elderly subjects . The present study was undertaken to address the reduced risk of falls and hip fractures in patients with long-st and ing stroke by vitamin D supplementation . METHODS Ninety-six elderly women with poststroke hemiplegia were followed for two years . Patients were r and omly assigned to one of the two groups , and 48 patients received 1,000 IU ergocalciferol daily , and the remaining 48 received placebo . The number of falls per person and incidence of hip fractures were compared between the two groups . Strength and tissue ATPase of skeletal muscles on the nonparetic side were assessed before and after the study . RESULTS At baseline , serum 25-hydroxyvitamin D levels were in the deficient range ( < 10 ng/ml ) in all patients ; and vitamin D treatment enhanced serum 25-hydroxyvitamin D and 1,25-dihydroxyvitamin D levels .  Vitamin D treatment accounted for a 59 % reduction in falls ( 95 % CI , 28 - 81 % ; p = 0.003 ) . There were increases in the relative number and size of type II muscle fibers and improved muscle strength in the vitamin D-treated group . Hip fractures occurred in 4 of 48 placebo group and 0 in 48 vitamin D2 group during the 2-year study period ( log-rank , p = 0.049 ) . CONCLUSION Vitamin D may increase muscle strength by improving atrophy of type II muscle fibers , which may lead to decreased falls and hip fractures We investigated the effects of vitamin D3 supplementation on physical performance during winter training in vitamin D insufficient taekwondo athletes . Thirty-five collegiate male and female taekwondo athletes , aged 19 - 22 years with low serum 25(OH)D concentration ( 28.8 ± 1.10 nmol/L ) , were r and omly assigned to a vitamin D group ( n = 20 ) or a placebo group ( n = 15 ) . Subjects received either a vitamin D3 capsule ( 5,000 IU/day ) or a placebo during 4 weeks of winter training . Blood sample s were collected for analyzing serum 25(OH)D concentration . Physical performance tests included Wingate anaerobic test , isokinetic muscle strength and endurance , a countermovement jump test , sit-ups , agility test , and 20-m pacer . Serum 25(OH)D concentrations increased significantly in the vitamin D group ( 96.0 ± 3.77 nmol/L ) after 4 weeks of supplementation , but no changes were found in the placebo group ( F = 242.44 , p = .000 ) . There were significant interaction effects for anaerobic peak power ( F = 7.49 , p = .010 ) and isokinetic knee extension at 180 deg/s ( F = 6.08 , p = .019 ) . Changes in serum 25(OH)D concentration were positively associated with changes in peak power and isokinetic knee extension at 180 deg/s . However , no significant interaction effects were observed in other performance variables . This study suggests that 4 weeks of vitamin D supplementation elevates serum 25(OH)D concentration to sufficient levels . Correcting vitamin D insufficiency improves some but not all aspects of performance . Thus , efficacy of vitamin D supplementation to enhance performance remains unclear Contracting human skeletal muscle is a major contributor to the exercise-induced increase of plasma interleukin-6 ( IL-6 ) . Although antioxidants have been shown to attenuate the exercise-induced increase of plasma IL-6 , it is unknown whether antioxidants inhibit transcription , translation or translocation of IL-6 within contracting human skeletal muscle . Using a single-blind placebo-controlled design with r and omization , young healthy men received an oral supplementation with either a combination of ascorbic acid ( 500 mg day(-1 ) ) and RRR-alpha-tocopherol ( 400 i.u . day(-1 ) ) ( Treatment , n= 7 ) , or placebo  ( Control , n= 7 ) . After 28 days of supplementation , the subjects performed 3 h of dynamic two-legged knee-extensor exercise at 50 % of their individual maximal power output . Muscle biopsies from vastus lateralis were obtained at rest ( 0 h ) , immediately post exercise ( 3 h ) and after 3 h of recovery ( 6 h ) . Leg blood flow was measured using Doppler ultrasonography . Plasma IL-6 concentration was measured in blood sample d from the femoral artery and vein . The net release of IL-6 was calculated using Fick 's principle . Plasma vitamin C and E concentrations were elevated in Treatment compared to Control . Plasma 8-iso-prostagl and in F(2alpha ) , a marker of lipid peroxidation , increased in response to exercise in Control , but not in Treatment . In both Control and Treatment , skeletal muscle IL-6 mRNA and protein levels increased between 0 and 3 h. In contrast , the net release of IL-6 from the leg , which increased during exercise with a peak at 3.5 h in Control , was completely blunted during exercise in Treatment . The arterial plasma IL-6 concentration from 3 to 4 h , when the arterial IL-6 levels peaked in both groups , was approximately 50 % lower in the Treatment group compared to Control ( Treatment versus Control : 7.9 pg ml(-1 ) , 95 % confidence interval ( CI ) 6.0 - 10.7 pg ml(-1 ) , versus 19.7 pg ml(-1 ) , CI 13.8 - 29.4 pg ml(-1 ) , at 3.5 h , P < 0.05 between groups ) . Moreover , plasma interleukin-1 receptor antagonist ( IL-1ra ) , C-reactive protein and cortisol levels all increased after the exercise in Control , but not in Treatment . In conclusion , our results show that supplementation with vitamins C and E attenuated the systemic IL-6 response to exercise primarily via inhibition of the IL-6 protein release from the contracting skeletal muscle per se This study determined if 6-weeks vitamin D2 supplementation ( vitD2 , 3800 IU/day ) had an influence on muscle function , eccentric exercise-induced muscle damage ( EIMD ) , and delayed onset of muscle soreness ( DOMS ) in National Association for Stock Car Auto Racing ( NASCAR ) NASCAR pit crew athletes . Subjects were r and omized to vitD2 ( n = 13 ) and placebo ( n = 15 ) , and ingested supplements ( double-blind ) for six weeks . Blood sample s were collected and muscle function tests conducted pre- and post- study ( leg-back and h and grip dynamometer strength tests , body weight bench press to exhaustion , vertical jump , 30-s Wingate test ) . Post- study , subjects engaged in 90 min eccentric-based exercise , with blood sample s and DOMS ratings obtained immediately after and 1- and 2-days post-exercise . Six weeks vitD2 increased serum 25(OH)D2 456 % and decreased 25(OH)D3 21 % versus placebo ( p < 0.001 , p = 0.036 , respectively ) , with no influence on muscle function test scores . The post- study eccentric exercise bout induced EIMD and DOMS , with higher muscle damage biomarkers measured in vitD2 compared to placebo ( myoglobin 252 % , 122 % increase , respectively , p = 0.001 ; creatine phosphokinase 24 h post-exercise , 169 % , 32 % , p < 0.001 ) , with no differences for DOMS . In summary , 6-weeks vitD2 ( 3800 IU/day ) significantly increased 25(OH)D2 and decreased 25(OH)D3 , had no effect on muscle function tests , and amplified muscle damage markers in NASCAR pit crew athletes following eccentric exercise
CONCLUSIONS Vitamin D supplementation positively affected lower limb muscle strength in athletes , but not upper limb muscle strength or muscle power .
Different muscle groups and functions may respond differently to vitamin D supplementation .
BACKGROUND Vitamin D may play a role in skeletal muscle because of the discovery of VDR in skeletal muscle .
However , vitamin D deficiency is a global problem , including athletes .
Studies examining the effect of vitamin D supplementation on muscle function in athletes have inconsistent results .
Therefore , we aim ed to quantitatively summarize the evidence for the effect of vitamin D supplementation on skeletal muscle strength and explosive power of athletes using a meta- analysis .