Superior Aerobic Capacity and Indices of Skeletal Muscle Morphology in Chronically Trained Master Endurance Athletes Compared With Untrained Older Adults

Abstract

The study aim was to comprehensively assess physiological function and muscle morphology in chronically trained older individuals against untrained young and older individuals. In a cross-sectional design, 15 young untrained controls (YC) (20 ± 2.7 years, 78.9 ± 13.3 kg), 12 untrained older controls (OC) (69.8 ± 4.1 years, 77.5 ± 14.2 kg), and 14 endurance-trained master athletes (MA) (67.1 ± 4.1 years, 68.7 ± 6.5 kg) underwent assessments of body composition, aerobic capacity, strength, muscle architecture, and fiber-type morphology. Skeletal muscle index was lower and body fat greater in OC versus MA. Estimated VO2max (mL·kg−1·minute−1) was similar between MA and YC, but lower in OC. Isometric leg strength normalized to fat-free mass was similar between groups, whereas normalized isometric arm strength was greater in YC than MA. Myosin heavy chain (MHC) I fiber area was greater in MA than OC, while MHC II fiber area was greater in YC than OC. MHC II fiber myonuclear domain size was greater in YC than OC and MA, whereas MA had greater MHC I and MHC II fiber capillarization than OC and YC. Satellite cell content was similar between groups. Chronic endurance training enhances indices of muscle morphology and improves body composition and aerobic capacity in older age, with potentially important implications for healthspan extension.

Absence of an aging‐related increase in fiber type grouping in athletes and non‐athletes

“…In fact, the absolute slope of the aging-related decrease in type II FCSA was higher in athletes than non-athletes and explains that while young athletes had larger muscle fibers than young non-athletes, no such difference in FCSA was seen between old athletes and non-athletes. Thus, in contrast to previous suggestions that regular physical activity preserves muscle mass and morphology 24,25,48,49 the absolute age-related gains in type II FCSA by regular physical activity were diminished in old age, but the relative gains were most likely similar.…”

Comparable Rates of Integrated Myofibrillar Protein Synthesis Between Endurance-Trained Master Athletes and Untrained Older Individuals

“…Generally, physical activity declines with advancing age (Jefferis et al, 2014) and inactivity and obesity may accelerate the development of muscle anabolic resistance and sarcopenia (Breen et al, 2013; Steffl et al, 2017). In contrast, MA, who have remained highly active through a large portion of adulthood maintain a healthy body composition and typically display superior physiological function and indices of muscle morphology compared with OC (Zampieri et al, 2015; McKendry et al, 2018, 2019). Nonetheless, it was recently demonstrated that middle-aged master triathletes aged ∼53 years display a blunted iMyoPS response to a downhill running stimulus compared with young triathletes aged ∼27 years (Doering et al, 2016).…”

“…Age-related muscle anabolic resistance is touted as a key mechanism contributing to the development and progression of sarcopenia (Shad et al, 2016) and is thought to be exacerbated by aspects of biological aging [i.e., inactivity, obesity (Smeuninx et al, 2017)]. Individuals that have undertaken regular structured exercise training throughout a large proportion of adulthood (MA), typically display superior physiological function and indices of muscle morphology compared with age-matched non-athletes (OC) (Zampieri et al, 2015; McKendry et al, 2018, 2019) and provide an opportunity to unpick the role of inherent and biological aging processes on muscle mass regulation (Lazarus and Harridge, 2007). However, there is a dearth of in vivo mechanistic information of muscle metabolic regulation in MA (McKendry et al, 2018).…”

“…Participant anthropometric and training characteristics are detailed in Table 1. In our recent work, we provided a comprehensive characterization of physiological function and muscle morphology in a larger sample of MA and OC, distinct from the volunteers recruited for the current study (McKendry et al, 2019). Thus, we chose not to repeat these measurements in the present study due to the required time commitment and instead focused on in vivo measurement of iMyoPS and intracellular signaling mechanisms.…”

“…Highly active older individuals who have maintained structured exercise training habits [Master Athletes, (MA)] display superior indices of physiological function (VO 2max and strength), muscle morphology and, typically, a more favorable body composition than their untrained age-matched counterparts (McKendry et al, 2018, 2019), which could potentially be explained by differences in MPS. The only study to date to investigate MPS in MA, reported that highly trained master triathletes (>50 years) displayed lower MPS rates following a bout of downhill running than younger triathletes (Doering et al, 2016).…”