Reduced volume but increased training intensity elevates muscle Na⁺-K⁺ pump α₁-subunit and NHE1 expression as well as short-term work capacity in humans

Abstract

Iaia FM, Thomassen M, Kolding H, Gunnarsson T, Wendell J, Rostgaard T, Nordsborg N, Krustrup P, Nybo L, Hellsten Y, Bangsbo J. Reduced volume but increased training intensity elevates muscle Na ϩ -K ϩ pump ␣1-subunit and NHE1 expression as well as short-term work capacity in humans.

Effect of intensified training on muscle ion kinetics, fatigue development, and repeated short-term performance in endurance-trained cyclists

“…In contrast, other studies implementing intense intermittent training have observed elevated levels of the Na ϩ -K ϩ pump subunits (3,18,34). In the study by Nielsen et al (34) untrained subjects had a higher content of the Na ϩ -K ϩ pump subunits ␣ 1 , ␣ 2 , and ␤ 1 after 8 wk of intense one-legged knee-extensor exercise, and the Na ϩ -K ϩ pump ␣ 1 and ␣ 2 subunits have also been shown to be upregulated in trained runners after 4 -9 wk of intensified and reduced training (3,18). The difference between these studies and the present study may be related to exercise modalities.…”

“…Ϫ exchanger (NKCC1) may have played a role in the altered K ϩ handling since in a recent study the expression of NKCC1 was higher (ϳ15%) after 4 wk of speed endurance training in trained runners (18). In the present study we were unable to examine changes in cell surface expression of ion transporting proteins and cannot, as such, exclude the possibility that changes in K ϩ handling are in part due to alterations in the cell surface expression of K ϩ transporting proteins such as the Na ϩ -K ϩ pump subunits, NKCC1, Kir2.1 and Kir6.2.…”

“…In trained subjects intense training would not be expected to change blood flow (24,46), thus any alteration in lactate and H ϩ release may be mediated by changes in transport proteins involved in lactate and H ϩ transport. Changes in MCT1 and NHE1 content in response to intensified training have been reported in some (6,15,18) but not all (3,44) studies in trained runners and soccer players. Thus it is unclear whether intensified training in combination with a reduced training volume induces changes in muscle ion transport proteins involved in lactate and H ϩ transport in trained athletes, and whether these changes leads to alterations in lactate and H ϩ release during intense exercise.…”

“…Studies on welltrained subjects, who increased their training intensity, have reported increased Na ϩ -K ϩ pump concentrations as determined by the [ 3 H]ouabain-binding technique (12,27). Iaia et al (18) and Bangsbo et al (3) found that intensified training with a concomitant reduction in training volume improved short-term performance and increased the amount of the Na ϩ -K ϩ pump subunits ␣ 1 and ␣ 2 leading to a lower arm venous K ϩ concentration during intense running. However, it is unknown whether the training actually changes muscle K ϩ kinetics.…”

Ultra short-term heart rate recovery after maximal exercise in continuous versus intermittent endurance athletes

“…Hence, athletes with faster recovery after brief intense exercise bouts are likely to perform better in intermittent sports. High-intensity interval training could be particularly well suited for improving intermittent endurance performance (Iaia et al 2008). As a result, it could be that a faster ultra short-term HRR reflects a positive adaptation to highintensity intermittent endurance training and, therefore, represents a superior capacity in performance events (Bosquet et al 2008;Lamberts et al 2009a).…”