Sequential Submaximal Training in Elite Male Rowers Does Not Result in Amplified Increases in Interleukin-6 or Hepcidin

Abstract

Previous research investigating single bouts of exercise have identified baseline iron status and circulating concentrations of interleukin-6 (IL-6) as contributors to the magnitude of postexercise hepcidin increase. The current study examined the effects of repeated training bouts in close succession on IL-6 and hepcidin responses. In a randomized, crossover design, 16 elite male rowers completed two trials, a week apart, with either high (1,000 mg) or low (<50 mg) calcium pre-exercise meals. Each trial involved two, submaximal 90-min rowing ergometer sessions, 2.5 hr apart, with venous blood sampled at baseline; pre-exercise; and 0, 1, 2, and 2.5 hr after each session. Peak elevations in IL-6 (approximately 7.5-fold, p < .0001) and hepcidin (approximately threefold, p < .0001) concentrations relative to baseline were seen at 2 and 3 hr after the first session, respectively. Following the second session, concentrations of both IL-6 and hepcidin remained elevated above baseline, exhibiting a plateau rather than an additive increase (2 hr post first session vs. 2 hr post second session, p = 1.00). Pre-exercise calcium resulted in a slightly greater elevation in hepcidin across all time points compared with control (p = .0005); however, no effect on IL-6 was evident (p = .27). Performing multiple submaximal training sessions in close succession with adequate nutritional support does not result in an amplified increase in IL-6 or hepcidin concentrations following the second session in male elite rowers. Although effects of calcium intake require further investigation, athletes should continue to prioritize iron consumption around morning exercise prior to exercise-induced hepcidin elevations to maximize absorption.

The Impact of Acute Calcium Intake on Bone Turnover Markers during a Training Day in Elite Male Rowers

“…Participants. Eighteen elite male rowers from the Rowing Australia National Training Centre, Canberra, in preparation for potential Olympic representation, were recruited for this study and a parallel study investigating iron and hepcidin responses (25). One participant with newly identified food intolerances was excluded because of his inability to complete one of the dietary arms, whereas another was unable to complete the required training load because of recent illness.…”

Iron regulation and absorption in athletes: contemporary thinking and recommendations

“…Ishibashi et al [7] found these elevated hepcidin levels were persistent (albeit marginally lower) at 22 h and 13 h following the first and second exercise sessions, respectively. Similarly, Fensham et al [8] examined the impact of two, 90 min submaximal (equivalent of individual rower's T1 power, defined as the power output at which capillary blood lactate reached 2 mmol/l) rowing ergometer sessions conducted 2.5 h apart by elite (Tier 4 [4]) athletes. These authors reported a significant elevation hepcidin levels at 3 h following the first exercise session, which remained elevated and plateaued for three hours after the second exercise bout.…”

Parenteral Iron Therapy: Examining Current Evidence for Use in Athletes

“…Unsurprisingly, in clinical populations with chronically elevated hepcidin levels (e. g. cancer, inflammatory conditions), parenteral iron administration is recommended as it overcomes the negative effect of hepcidin on GI absorption [27]. In athletes, where repeated exercise-induced elevations of hepcidin occur daily [17,28], the limitations to gut absorption of oral iron intake may be substantial. Interestingly, the amount of hepcidin required to block iron absorption from the gut is lower than that required to block iron recycling from macrophages, where intravenous (IV) iron is taken up [29].…”