Aging related changes in determinants of muscle force generating capacity: A comparison of muscle aging in men and male rodents

Quantitative analysis of the renal aging in rats. Stereological study

“…Another point to be considered is the fact that endogenous creatinine is produced in the organism to be directly proportional to the muscular mass. In Wistar rats, the decline in the muscular mass is very small (approximately 5%), whereas in men these values are around 25% reduction 15 With strong statistical significance, the gradual reduction of the glomerular volume density and the glomerular numerical density found in the stereological analysis of the renal tissue of the rats in the groups of animals gradually older, clearly demonstrates the process of renal aging as already well-established in literature [17][18][19][20][21] .…”

Plantaris muscle weakness in old mice: relative contributions of changes in specific force, muscle mass, myofiber cross-sectional area, and number

“…The decreases in maximal muscle force observed in this and other mice studies are rather small, compared to the effects reported at a similar relative mean life expectancy in humans (see, for review, Ballak et al 2014). Nevertheless, the 13 % decrease in muscle strength between 9-and 25 months of age in our C57BL/6J mice is comparable to that between the age of 25-30-year-old and 60-70-year-old humans (Ballak et al 2014).…”

“…The discrepancy between the effects of aging on muscle mass and maximal force shown in our study and those previously reported is unlikely related to the muscles used, as other studies observed the effects of aging in both fast and slow muscles. It is more likely that the use of older animals (26-28 months) in other studies than in our study (25 months) contributes to the discrepancy, as larger effects of aging on maximal muscle force are likely to be observed in the older the animal (Ballak et al 2014;Brooks and Faulkner 1988;Lynch et al 2001;McArdle et al 2004). Indeed, Chan and Head (2010) observed that even in 20-22-month-old mice, specific force was already reduced without significant muscle atrophy.…”

“…In the human m. vastus lateralis, this amounted to approximately 30 % between 40 and 80 years (Janssen et al 2000;Klitgaard et al 1990;Maden-Wilkinson et al 2014;Overend et al 1992; Rice et al 1989;Young et al 1984;Young et al 1985). In rodents, at ages representative of these ages in humans, a similar age-related reduction in muscle mass is observed (Ballak et al 2014). Typically, the agerelated decrease in muscle mass is due to both a reduction in myofiber number (Lexell et al 1988;Lushaj et al 2008;McKiernan et al 2004;Sato et al 1984;Zerba et al 1990) and (preferential type II) myofiber atrophy (Brown and Hasser 1996;Carter et al 2010;Klitgaard et al 1990;Larsson 1978;Tomonaga 1977;Verdijk et al 2007).…”

“…Muscle force generating capacity in humans can decrease as much as 60 % between the age of 30 and 80 years (Faulkner et al 2007). Also in rodents, a 25-65 % age-related deterioration in the muscle force generating capacity has been reported (Ballak et al 2014;Brooks and Faulkner 1988;Carter et al 2010;Degens and Alway 2003), which is not only due to a loss of muscle mass but also a reduction in the force-generating capacity per muscle crosssectional area, specific force (Degens et al 2009). It could be that during the initial stages of sarcopenia a reduction in specific force precedes the loss in muscle mass.…”