Changes in metabolism but not myocellular signaling by training with CHO-restriction in endurance athletes.

Kasper D Gejl,Torben Rokkedal-Lausch,Anne-Kristine Meinild Lundby,Kurt Jensen,Hans-Christer Holmberg,Lars Nybo,Line Thams,Niels Ørtenblad,Peter Plomgaard,Kristian Vissing,Mette Hansen

doi:10.14814/phy2.13847

Abstract

Carbohydrate (CHO) restricted training has been shown to increase the acute training response, whereas less is known about the acute effects after repeated CHO restricted training. On two occasions, the acute responses to CHO restriction were examined in endurance athletes. Study 1 examined cellular signaling and metabolic responses after seven training‐days including CHO manipulation (n = 16). The protocol consisted of 1 h high‐intensity cycling, followed by 7 h recovery, and 2 h of moderate‐intensity exercise (120SS). Athletes were randomly assigned to low (LCHO: 80 g) or high (HCHO: 415 g) CHO during recovery and the 120SS. Study 2 examined unaccustomed exposure to the same training protocol (n = 12). In Study 1, muscle biopsies were obtained at rest and 1 h after 120SS, and blood samples drawn during the 120SS. In Study 2, substrate oxidation and plasma glucagon were determined. In Study 1, plasma insulin and proinsulin C‐peptide were higher during the 120SS in HCHO compared to LCHO (insulin: 0 min: +37%; 60 min: +135%; 120 min: +357%, P = 0.05; proinsulin C‐peptide: 0 min: +32%; 60 min: +52%; 120 min: +79%, P = 0.02), whereas plasma cholesterol was higher in LCHO (+15–17%, P = 0.03). Myocellular signaling did not differ between groups. p‐AMPK and p‐ACC were increased after 120SS (+35%, P = 0.03; +59%, P = 0.0004, respectively), with no alterations in p‐p38, p‐53, or p‐CREB. In Study 2, glucagon and fat oxidation were higher in LCHO compared to HCHO during the 120SS (+26–40%, P = 0.03; +44‐76%, P = 0.01 respectively). In conclusion, the clear respiratory and hematological effects of CHO restricted training were not translated into superior myocellular signaling after accustomization to CHO restriction.

Highlights

Endurance training is a salient and powerful stimulus to induce both cellular and cardiovascular adaptations, and to improve aerobic capacity and performance
While the blood glucose remained stable in the LCHO group, it fluctuated during the CHO manipulated training protocol in the HCHO group, eventually being similar to Rest after the 120-min training session of moderate intensity (120SS) (5.3 Æ 0.9 mmol LÀ1)
Repeating the same CHO manipulated training protocol seems to prevent perturbations in blood glucose. This is the first study to investigate the acute response to multiple days of CHO restricted training, on substrate utilizatoin and myocellular signaling in highly trained endurance athletes

Summary

Introduction

Endurance training is a salient and powerful stimulus to induce both cellular and cardiovascular adaptations, and to improve aerobic capacity and performance. Numerous training strategies have been investigated in highly trained endurance athletes to optimize training outcomes and athletic performance, including restriction of carbohydrate (CHO) intake either before, during, or after exercise Physiological Reports published by Wiley Periodicals, Inc. on behalf of The Physiological Society and the American Physiological Society. A deliberate change in the metabolism and substrate utilization by training with energy- or CHO restriction may be a strategy to improve the training response and endurance performance

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