Effect of low energy availability during three consecutive days of endurance training on iron metabolism in male long distance runners.

Aya Ishibashi,Tsutomu Hiroyama,Akiko Kamei,Chihiro Kojima,Kazushige Goto,Kaito Iwayama,Toshiki Tsuji,Yoko Tanabe,Hideyuki Takahashi

doi:10.14814/phy2.14494

Abstract

We investigated the effect of low energy availability (LEA) during three consecutive days of endurance training on muscle glycogen content and iron metabolism. Six male long distance runners completed three consecutive days of endurance training under LEA or neutral energy availability (NEA) conditions. Energy availability was set at 20 kcal/kg fat‐free mass (FFM)/day for LEA and 45 kcal/kg FFM/day for NEA. The subjects ran for 75 min at 70% of maximal oxygen uptake ( V˙O2max) on days 1–3. Venous blood samples were collected following an overnight fast on days 1–4, immediately and 3 hr after exercise on day 3. The muscle glycogen content on days 1–4 was evaluated by carbon‐magnetic resonance spectroscopy. In LEA condition, the body weight and muscle glycogen content on days 2–4, and the FFM on days 2 and 4 were significantly lower than those on day1 (p < .05 vs. day1), whereas no significant change was observed throughout the training period in NEA condition. On day 3, muscle glycogen content before exercise was negatively correlated with serum iron level (immediately after exercise, 3 hr after exercise), serum hepcidin level immediately after exercise, and plasma IL‐6 level immediately after exercise (p < .05). Moreover, serum hepcidin level on day 4 was significantly higher in LEA condition than that in NEA condition (p < .05). In conclusion, three consecutive days of endurance training under LEA reduced the muscle glycogen content with concomitant increased serum hepcidin levels in male long distance runners.

Highlights

Iron deficiency is a highly prevalent nutritional disorder among endurance athletes (Beard & Tobin, 2000)
We hypothesized that low energy availability (LEA) during the endurance training period would increase the IL-6 and hepcidin levels with decreased muscle glycogen content
The major finding of the present study was that three consecutive days of endurance training under LEA significantly increased the resting serum hepcidin levels with concomitant reduction of muscle glycogen content elevated hepcidin was not associated with inflammation

Summary

| INTRODUCTION

Iron deficiency is a highly prevalent nutritional disorder among endurance athletes (Beard & Tobin, 2000). The influence of manipulation of CHO intake (3 vs 10 g/kg BW) after a glycogen-depleting run on the exercise-induced hepcidin response on the following day was previously investigated. Reduced EI, in particular lowered CHO intake, during endurance period training may promote elevation of the hepcidin level. LEA is frequently observed in endurance athletes (e.g., marathon runners) during daily training (Loucks, 2007), and it may increase the risk of iron deficiency (Petkus, Murray-Kolb, & De Souza, 2017). We investigated the impact of LEA during three-consecutive days of endurance training on the muscle glycogen content and iron metabolism in male long-distance runners. We hypothesized that LEA during the endurance training period would increase the IL-6 and hepcidin levels with decreased muscle glycogen content

| MATERIALS AND METHODS

| RESULTS

Findings

| DISCUSSION

| CONCLUSION