The effect of acute vs chronic magnesium supplementation on exercise and recovery on resistance exercise, blood pressure and total peripheral resistance on normotensive adults.

Lindsy S Kass,Filipe Poeira

doi:10.1186/s12970-015-0081-z

Abstract

BackgroundMagnesium supplementation has previously shown reductions in blood pressure of up to 12 mmHg. A positive relationship between magnesium supplementation and performance gains in resistance exercise has also been seen. However, no previous studies have investigated loading strategies to optimise response. The aim of this study was to assess the effect of oral magnesium supplementation on resistance exercise and vascular response after intense exercise for an acute and chronic loading strategy on a 2-day repeat protocol.MethodsThe study was a randomised, double-blind, cross-over design, placebo controlled 2 day repeat measure protocol (n = 13). Intense exercise (40 km time trial) was followed by bench press at 80% 1RM to exhaustion, with blood pressure and total peripheral resistance (TPR) recorded. 300 mg/d elemental magnesium was supplemented for either a 1 (A) or 4 (Chr) week loading strategy. Food diaries were recorded.ResultsDietary magnesium intake was above the Reference Nutrient Intake (RNI) for all groups. Bench press showed a significant increase of 17.7% (p = 0.031) for A on day 1. On day 2 A showed no decrease in performance whilst Chr showed a 32.1% decrease. On day 2 post-exercise systolic blood pressure (SBP) was significantly lower in both A (p = 0.0.47) and Chr (p = 0.016) groups. Diastolic blood pressure (DBP) showed significant decreases on day 2 solely for A (p = 0.047) with no changes in the Chr. TPR reduced for A on days 1 and 2 (p = 0.031) with Chr showing an increase on day 1 (p = 0.008) and no change on day 2.ConclusionThere was no cumulative effect of Chr supplementation compared to A. A group showed improvement for bench press concurring with previous research which was not seen in Chr. On day 2 A showed a small non-significant increase but not a decrement as expected with Chr showing a decrease. DBP showed reductions in both Chr and A loading, agreeing with previous literature. This is suggestive of a different mechanism for BP reduction than for muscular strength. TPR showed greater reductions with A than Chr, which would not be expected as both interventions had reductions in BP, which is associated with TPR.

Highlights

Magnesium supplementation has previously shown reductions in blood pressure of up to 12 mmHg
Performance Bench press Net strength gains as determined by 1-RM showed significant increase of 17.7% with the acute Mg2+ loading strategy compared to baseline (p = 0.031) (Figure 1)
As has been shown previously [13,21] acute magnesium supplementation has a positive effect on BP, plyometric parameters and torque, its effect on resistance exercise has not been evident to date

Summary

Introduction

Magnesium supplementation has previously shown reductions in blood pressure of up to 12 mmHg. Micronutrient intake has been highlighted to have gained greater prominence with athletes in relation to the importance of an adequate nutritional status [5], previous research highlights nutritional inadequacies and an impaired nutritional status (i.e. marginal nutrient deficiency) from both an athletic [5] and general population perspective [6]. This identifies physical activity as increasing the rate at which micronutrients are utilised, promoting excessive micronutrient loss via increased catabolism and excretion (sweat and urine). This, together with a decline in dietary intake below the RNI may have a negative impact on both performance and blood pressure

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