Moreover, a bonus outcome of eccentric training would be a non-negligible increase in muscle mass and strength, which is particularly interesting for individuals in whom skeletal muscle mass is compromised due to chronic disease, sarcopenia, and/or aging ( Ellis et al., 2015 Cruz-Jentoft et al., 2019). Indeed, in individuals with a limited capacity to reach and sustain exercise intensities high enough for significant functional gains to be seen using traditional physical conditioning, the use of an eccentric modality with lower cardiorespiratory demand represents a valuable alternative. Endurance eccentric exercise is characterized by lower cardiorespiratory demands ( Perrey et al., 2001 Minetti et al., 2002 Dufour et al., 2004 Chavanelle et al., 2014), which makes it particularly attractive for use in patients with chronic heart and lung diseases or with muscle impairments ( Roig et al., 2008). An activity that involves predominantly eccentric contractions can be described as an eccentric exercise, such as downhill running/walking or eccentric cycling, using a specifically designed ergometer ( LaStayo et al., 2003). In regular daily movement, concentric and eccentric muscle contractions are combined, for example, when using the stairs or when braking a fall or lowering a heavy object. Since its first description at the end of the 19th century ( Fick, 1881), eccentric exercise has sparked much interest on account of distinctive features enabling high external mechanical power at reduced cost and its potential for positive rehabilitation and training outcomes ( Hoppeler, 2016). The implications of observations to date are discussed within future perspectives for advancing research on endurance eccentric exercise physiological impacts and using a combined eccentric and concentric exercise approach to optimize functional capacity. The summary of findings does not reveal an impact of training on skeletal muscle mitochondrial respiration nor on selected mitochondrial messenger RNA transcripts. The article examines the protection provided by repeated bouts of acute eccentric exercise and reports on the impact of eccentric cycling and downhill running training programs on markers of mitochondrial function and of mitochondrial biogenesis using mostly from animal studies. Given the high damage susceptibility of eccentric exercise, the extent to which skeletal muscle oxygen utilization adaptations would be seen depends on the balance of adverse and positive signals on mitochondrial integrity. The impact of endurance eccentric training on peripheral flow distribution remains largely undocumented. By extension, it can be inferred that the very high eccentric power output that would have been required to solicit a metabolic demand sufficient to enhance peak aerobic power could not be tolerated or sustained by participants. Observations to date indicate that overall, the aerobic demand associated with the eccentric training load was too low to significantly increase peak maximal oxygen consumption. In the studies reviewed, specially designed cycle-ergometers or downhill treadmill running were used to generate eccentric contractions.

This article reviews the existing evidence for endurance eccentric exercise effects on the components of the oxygen transport system from systemic to mitochondria in both humans and animals. Less is known, however, regarding its impact on oxygen transport and on factors to be considered for optimizing its prescription and monitoring. Current evidence concurs to show that eccentric training translates into considerable gains in muscle mass and strength. 5Unité d’Exploration en Nutrition (UEN), CRNH Auvergne, Clermont-Ferrand, FranceĪ characteristic feature of eccentric as compared with concentric exercise is the ability to generate greater mechanical loads for lower cardiopulmonary demands.4Respiratory Division, McGill University Health Center, Montreal, QC, Canada.

3Service de Médecine Physique et de Réadaptation, CHU Gabriel Montpied/CHU Louise Michel, Clermont-Ferrand, France.2Service de Médecine du Sport et des Explorations Fonctionnelles, CHU Gabriel Montpied, Clermont-Ferrand, France.1UCA–INRAE, Human Nutrition Unit, ASMS Team, University Clermont Auvergne, Clermont-Ferrand, France.Julianne Touron 1* Frédéric Costes 1,2 Emmanuel Coudeyre 1,3 Hélène Perrault 4 Ruddy Richard 1,2,5

Different muscular endurance exercises