Magnesium and phase angle: a prognostic tool for monitoring cellular integrity in judo athletes

Adequate magnesium (Mg) levels play a vital role in membrane excitability, cell contractility and metabolism, being a key nutrient for sustaining appropriate muscular contraction and performance levels in athletes. Phase angle (PhA), assessed by bioimpedance analysis (BIA), has been reported to be positively associated with most nutritional markers and is an indicator of membrane integrity and water distribution between intra- and extracellular spaces. The aim of the present study was to verify the association between Mg status and PhA as a predictor of cellular health, in a sample of judo athletes from a period of weight stability to prior to competition. Judo athletes (n = 20) from the national team were evaluated on two occasions: during a period when body weight was stable (M1), and prior to competition (M2). Changes between these occasions were calculated as M2-M1. PhA was obtained by bioelectrical impedance spectroscopy at a frequency of 50 KHz. Mg was measured in serum and red blood cells (RBC) by atomic absorption spectrophotometry, and Mg in the diet was assessed from a 24-h diet record over a seven-day period, after an assessment of body composition. Mean PhA did not differ from M1 to M2. However, individual changes in PhA were positively associated with individual changes in serum (r = 0.62, p = 0.004) and RBC Mg (r = 0.45, p = 0.048). This association was independent of weight changes between assessments, but when adjusted for Mg intake changes, only the association between PhA and serum Mg remained significant. These results highlight that in elite athletes PhA may be an indirect indicator of muscular function.