Effects of Resistance Exercise with or without Whey Protein Supplementation on Ocular Changes after a 21-Day Head-Down Bed Rest.

Marc Kermorgant,Jean-Claude Quintyn,Vincent Soler,Sirine Hammoud,Thomas Geeraerts,Anne Pavy-Le Traon,Marie-Pierre Bareille,Arnaud Beck,Laurence Mahieu

doi:10.3390/life11080741

Abstract

Neuro-ophthalmological changes have been reported after prolonged exposure to microgravity; however, the pathophysiology remains unclear. The objectives of the present study were twofold: (1) to assess the neuro-ophthalmological impact of 21 days of head-down bed rest (HDBR) and (2) to determine the effects of resistance vibration exercise (RVE) alone or combined with nutritional supplementation (NeX). In this case, 12 healthy male subjects completed three interventions of a 21-day HDBR: a control condition without countermeasure (CON), a condition with resistance vibration exercise (RVE) comprising of squats, single leg heel and bilateral heel raises and a condition using also RVE associated with nutritional supplementation (NeX). Intraocular pressure (IOP) was assessed by applanation tonometry. Retinal nerve fiber layer thickness (RNFLT) was assessed with spectral-domain optical coherence tomography, before HDBR and between Day 2 and Day 4 after each session of HDBR. In CON condition, IOP was preserved; while in RVE and NeX conditions, IOP was increased. In CON condition, RNFLT was preserved after HDBR. RVE and NeX conditions did not have significant effects on RNFLT. This study showed that a 3-week HDBR did not induce significant ophthalmological changes. However, RVE induced an elevation in IOP after HDBR. Nutritional supplementation did not reduce or exacerbate the side effects of RVE.

Highlights

Some crewmembers who underwent the environment on the International Space Station during several months, exhibited a large panel of ophthalmologic issues including enlargement in optic nerve sheath diameter, a rise in intraocular pressure (IOP), papilledema, increase in circumpapillary retinal nerve fiber layer thickness (RNFLT), optic disc edema, choroidal folds, hyperopic shift, globe flattening, etc
Intraocular pressure preserved after head-down bed rest, but impaired with resistance exercise with or without nutritional supplementation
The frequency of exercise was only performed twice a week, which may limit the effects of the countermeasures. These findings suggest that 21 days of head-down bed rest (HDBR) did not induce significant ophthalmological changes

Summary

Introduction

Some crewmembers who underwent the environment on the International Space Station during several months, exhibited a large panel of ophthalmologic issues including enlargement in optic nerve sheath diameter, a rise in intraocular pressure (IOP), papilledema, increase in circumpapillary retinal nerve fiber layer thickness (RNFLT), optic disc edema, choroidal folds, hyperopic shift, globe flattening, etc. All these phenomena may reflect a 4.0/). The description of these visual changes is questioning the medical space community on safety aspects of long duration spaceflights

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