Resistance training upregulates skeletal muscle Na⁺, K⁺-ATPase content, with elevations in both α₁ and α₂, but not β...

The Na⁺, K⁺-ATPase (NKA) is important in regulating trans-membrane ion gradients, cellular excitability and muscle function. We investigated the effects of resistance training in healthy young adults on the adaptability of NKA content and of the specific α and β isoforms in human skeletal muscle.

Twenty-one healthy young males (22.9 ± 4.6 year; 1.80 ± 0.70 m, 85.1 ± 17.8 kg, mean ± SD) underwent 7 weeks of resistance training, training three times per week (RT, n = 16) or control (CON, n = 5). The training program was effective with a 39% gain in leg press muscle strength (p = 0.001). A resting vastus lateralis muscle biopsy was taken before and following RT or CON and assayed for NKA content ([³H]ouabain binding site content) and NKA isoform (α₁, α₂, β_1, β₂) abundances.

After RT, each of NKA content (12%, 311 ± 76 vs 349 ± 76 pmol g wet weight^-1, p = 0.01), NKA α₁ (32%, p = 0.01) and α₂ (10%, p < 0.01) isoforms were increased, whereas β₁ (p = 0.18) and β₂ (p = 0.22) isoforms were unchanged. NKA content and isoform abundances were unchanged during CON.

Resistance training increased muscle NKA content through upregulation of both α₁ and α₂ isoforms, which were independent of β isoform changes. In animal models, modulations in α₁ and α₂ isoform abundances in skeletal muscle may affect fatigue resistance during exercise, muscle hypertrophy and strength. Whether similar in-vivo functional benefits of these NKA isoform adaptations occurs in human muscle with resistance training remains to be determined.