Muscle metabolism in older subjects using ³¹P magnetic resonance spectroscopy

Abstract

We used phosphorus magnetic resonance spectroscopy to study the calf muscles of elderly normal (mean +/- SD) (80.0 +/- 5.12 years), elderly impaired (80.7 +/- 0.58 years), old normal (66.8 +/- 1.92 years), and young normal people (24.6 +/- 4.72 years). Relative levels of inorganic phosphate (Pi), phosphocreatine (PCr), and adenosine triphosphate were measured with a 1.9-tesla, 30-cm bore magnet at rest and following plantra flexon exercise. No differences were found at rest or during recovery from exercise in the elderly normal subjects with respect to gender or the presence of stable medical problems treated with medication. At rest there was an age-related decrease in the ratio of PCr/Pi. After exercise, the time constant of PCr recovery increased with age. A mild 7-week exercise regimen consisting of plantar flexion had no effect on time constant of PCr recovery in the elderly subjects. Four elderly impaired subjects had lower PCr/Pi ratios at rest and slower time constant of PCr recovery after exercise than normal elderly subjects. We conclude that gender and the presence of stable medical problems had no effect on muscle metabolism in the elderly and that the elderly recovered slower than young controls. This slower recovery was not corrected with a mild exercise program.

Effect of age on in vivo oxidative capacity in two locomotory muscles of the leg

“…They are not consistent with the results of one in vivo study (McCully et al 1991) and two in vitro (enzyme activities) studies (Coggan et al 1992;Houmard et al 1998), all of which showed lower oxidative capacity in the O subjects. In the first study (McCully et al 1991), the lack of control for PA and health status of the O subjects likely contributed to lower oxidative capacity in that group. The discrepancy between the present results and those of the two in vitro studies is less clear, as both only studies included only people who reported that they were sedentary.…”

“…In contrast with studies of the TA, other studies have shown age-related declines in oxidative capacity of the plantarflexor muscles using both in vivo (McCully et al 1991) and in vitro approaches (e.g., enzyme activities; Coggan et al 1992;Houmard et al 1998). In the quadriceps muscles, which are most commonly studied, in vivo (Conley et al 2000;Larsen et al 2012b) and in vitro (Short et al 2005) oxidative capacities are both lower in O adults.…”

“…The TA is largely composed of type I fibers (75 % type I; Gregory et al 2001), while the MG is mixed in fibertype composition (50 % type I; Edgerton et al 1975). Furthermore, while most studies of the TA do not report lower oxidative capacity in O adults (Kent-Braun and Ng 2000; Lanza et al 2005Lanza et al , 2007Larsen et al 2012b;Tevald et al 2010), reports on the MG differ, with studies reporting either lower (McCully et al 1991;Coggan et al 1992;Houmard et al 1998) or similar (Chilibeck et al 1998;Wray et al 2009) oxidative capacity in O compared to Y adults. Based on the previously discussed evidence that age-related changes in several aspects of muscle performance are smaller in the TA than the MG, we hypothesized that oxidative capacity would be preserved in the TA, but not the MG, of O subjects.…”

“…For example, oxidative capacity, which is one measure of mitochondrial function, has been reported by some to decline in older (O) adults (Conley et al 2000;Short et al 2005;Coggan et al 1992;McCully et al 1991;Pastoris et al 2000;Karakelides et al 2010), while others report no change with aging Larsen et al 2012b;Hutter et al 2007;Rasmussen et al 2003;Tevald et al 2010;Chilibeck et al 1998). A number of factors, including the means of assessing mitochondrial function, the health and physical activity (PA) status of the study participants, and the muscle group studied, apparently contribute to these conflicting findings (Larsen et al 2012b).…”

Regional Difference of Muscle Oxygen Saturation and Blood Volume during Exercise Determined by Near Infrared Imaging Device.

“…In humans, regional differences could result not only from regional differences in intramuscular pressure, but also from disease. Atherosclerosis can significantly reduce oxygen delivery to skeletal muscle [17][18][19][20], and the progression of atherosclerosis is unevenly distributed among conduit arteries [21]. Thus the development of a new noninvasive method for determining regional differences in oxygen status in humans is of great potential value.…”