Interspersed normoxia during live high, train low interventions reverses an early reduction in muscle Na+, K+ATPase activity in well-trained athletes

Abstract

Hypoxia and exercise each modulate muscle Na(+), K(+)ATPase activity. We investigated the effects on muscle Na(+), K(+)ATPase activity of only 5 nights of live high, train low hypoxia (LHTL), 20 nights consecutive (LHTLc) versus intermittent LHTL (LHTLi), and acute sprint exercise. Thirty-three athletes were assigned to control (CON, n = 11), 20-nights LHTLc (n = 12) or 20-nights LHTLi (4 x 5-nights LHTL interspersed with 2-nights CON, n = 10) groups. LHTLc and LHTLi slept at a simulated altitude of 2,650 m (F(I)O(2) 0.1627) and lived and trained by day under normoxic conditions; CON lived, trained, and slept in normoxia. A quadriceps muscle biopsy was taken at rest and immediately after standardised sprint exercise, before (Pre) and after 5-nights (d5) and 20-nights (Post) LHTL interventions and analysed for Na(+), K(+)ATPase maximal activity (3-O-MFPase) and content ([(3)H]-ouabain binding). After only 5-nights LHTLc, muscle 3-O-MFPase activity declined by 2% (P < 0.05). In LHTLc, 3-O-MFPase activity remained below Pre after 20 nights. In contrast, in LHTLi, this small initial decrease was reversed after 20 nights, with restoration of 3-O-MFPase activity to Pre-intervention levels. Plasma [K(+)] was unaltered by any LHTL. After acute sprint exercise 3-O-MFPase activity was reduced (12.9 +/- 4.0%, P < 0.05), but [(3)H]-ouabain binding was unchanged. In conclusion, maximal Na(+), K(+)ATPase activity declined after only 5-nights LHTL, but the inclusion of additional interspersed normoxic nights reversed this effect, despite athletes receiving the same amount of hypoxic exposure. There were no effects of consecutive or intermittent nightly LHTL on the acute decrease in Na(+), K(+)ATPase activity with sprint exercise effects or on plasma [K(+)] during exercise.

Four weeks of normobaric “live high-train low” do not alter muscular or systemic capacity for maintaining pH and K+ homeostasis during intense exercise

“…Furthermore, 21 days of gradual ascent to 6,194 m and subsequent decent have been found to reduce muscle Na ϩ -K ϩ pump expression by ϳ14% (20). However, 23 days of LHTL do not affect Na ϩ -K ϩ pump protein expression or plasma K ϩ during exercise (1,35), which is in agreement with the present observations. Thus it appears that K ϩ homeostasis and Na ϩ -K ϩ pump expression may be affected by prolonged severe hypoxic exposure, but not by 4 wk of LHTL at ϳ3,000 m.…”

Paradoxical effects of endurance training and chronic hypoxia on myofibrillar ATPase activity

“…Number (n) of samples analyzed is indicated in parentheses. and significant depressive effects of hypoxia on Na ϩ -K ϩ -ATPase activity were reported (1,18,19), suggesting an occurrence of an adaptive mechanism also present in ATPase pump activity.…”

Advancing hypoxic training in team sports: from intermittent hypoxic training to repeated sprint training in hypoxia

“…Hence, IHT presents the advantages of minimal travel and relatively low expense and causes limited disruption to the athletes’ normal training environment and lifestyle. Another advantage is that it also avoids the deleterious effect (decreased muscle excitability) of an extended stay in altitude 6. By adding the stress of hypoxia during ‘aerobic’ or ‘anaerobic’ interval training (INT), it is believed that IHT would potentiate greater performance improvements compared to similar training at sea level.…”