3日間連続の持久力トレーニング中の低エネルギー摂取が男性長距離ランナーの鉄代謝に及ぼす影響

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

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

抄録

3日間連続した持久力トレーニング中の低エネルギーアベイラビリティ（LEA）が筋グリコーゲン含量と鉄代謝に与える影響を調査した。男性長距離ランナー6名を対象に、LEAまたはニュートラルエネルギーアベイラビリティ（NEA）条件で3日間連続の持久力トレーニングを実施した。エネルギー利用可能量は、LEAでは20kcal/kgの無脂肪質量（FFM）/日、NEAでは45kcal/kgのFFM/日とした。被験者は1～3日目に最大酸素摂取量( O )の70%で75分間走行した。1～4 日目の一晩絶食後、3 日目の運動直後と 3 時間後に静脈血を採取した。1～4 日目の筋グリコーゲン含量は炭素磁気共鳴分光法で評価した。LEA条件では、2〜4日目の体重および筋グリコーゲン含量、2日目および4日目のFFMは、1日目に比べて有意に低かった（p<.05 vs. 1日目）が、NEA条件ではトレーニング期間を通して有意な変化は観察されなかった。3日目、運動前の筋グリコーゲン含量は、運動直後の血清鉄値（運動直後、運動後3時間）、運動直後の血清ヘプチジン値、運動直後の血漿IL-6値と負の相関を示した（p<.05）。さらに、4日目の血清ヘプチジン値は、LEA条件の方がNEA条件よりも有意に高かった(p<.05)。結論として、3日間連続してLEA条件下での持久力トレーニングは、男性長距離ランナーの筋グリコーゲン含量を減少させ、同時に血清ヘプチジン値を上昇させた。

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 ( O ) 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.

© 2020 The Authors. Physiological Reports published by Wiley Periodicals LLC on behalf of The Physiological Society and the American Physiological Society.