Mitochondrial impairment is hypothesized to contribute to the pathogenesis of insulin resistance. Mitofusin (Mfn) proteins regulate the biogenesis and maintenance of the mitochondrial network, and when inactivated, cause a failure in the mitochondrial architecture and decreases in oxidative capacity and glucose oxidation. Exercise increases muscle mitochondrial content, size, oxidative capacity and aerobic glucose oxidation. To address if Mfn proteins are implicated in these exercise-induced responses, we measured Mfn1 and Mfn2 mRNA levels, pre-, post-, 2 and 24 h post-exercise. Additionally, we measured the expression levels of transcriptional regulators that control mitochondrial biogenesis and functions, including PGC-1α, NRF-1, NRF-2 and the recently implicated ERRα. We show that Mfn1, Mfn2, NRF-2 and COX IV mRNA were increased 24 h post-exercise, while PGC-1α and ERRα mRNA increased 2 h post-exercise. Finally, using in vitro cellular assays, we demonstrate that Mfn2 gene expression is driven by a PGC-1α programme dependent on ERRα. The PGC-1α/ERRα-mediated induction of Mfn2 suggests a role of these two factors in mitochondrial fusion. Our results provide evidence that PGC-1α not only mediates the increased expression of oxidative phosphorylation genes but also mediates alterations in mitochondrial architecture in response to aerobic exercise in humans.

Aim: To compare single-leg balance performance between subacute ankle sprain patients receiving no exercise therapy and healthy persons.Methods: Forty-eight subacute ankle sprain patients (age = 34.3 ±9.7 years) and 10 healthy persons (age = 30.1 ±4.7 years) participated in the study. Participants underwent an assessment of body functions and a 30-second single-leg balance test on a force plate under stable and unstable conditions. Center of pressure (COP) range, length and speed in mediolateral (ML) and anteroposterior (AP) directions were calculated.Results: All healthy persons finished the 30-second balance test under both conditions. Forty-three patients (90%; P=.374) were able to complete the test on the stable surface and 38 patients (79%; P=.125) on the unstable surface. Ankle sprain patients showed increased COP AP speed compared to healthy persons for stable conditions (P=.009) and a larger COP AP range for unstable conditions (P=.001). Furthermore, muscle strength in inversion and eversion were correlated to COP performance (P<.050). Conclusion:Specific ankle strength exercises, including muscle strength exercises in the frontal plane, might improve balance performance in ankle sprain patients.