The impact of obesity on skeletal muscle architecture in untrained young vs. old women

Abstract

It is unknown whether loading of the lower limbs through additional storage of fat mass as evident in obesity would promote muscular adaptations similar to those seen with resistance exercise. It is also unclear whether ageing modulates any such adjustments. This study aimed to examine the relationships between adiposity, ageing and skeletal muscle size and architecture. A total of 100 untrained healthy women were categorised by age into young (Y) (mean AE SD: 26.7 AE 9.4 years) vs. old (O) (65.1 AE 7.2 years) and body mass index (BMI) classification (underweight, normal weight, overweight and obese). Participants were assessed for body fat using dual energy x-ray absorptiometry, and for gastrocnemius medialis (GM) muscle architecture (skeletal muscle fascicle pennation angle and length) and size [GM muscle volume and physiological cross-sectional area (PCSA)] using B-mode ultrasonography. GM fascicle pennation angle (FPA) in the obese Y females was 25% greater than underweight (P = 0.001) and 25% greater than normal weight (P = 0.001) individuals, while O females had 32 and 22% greater FPA than their underweight (P = 0.008) and normal weight (P = 0.003) counterparts. Furthermore, FPA correlated with body mass in both Y and O females (Y r = 0.303; P < 0.001; O r = 0.223; P = 0.001), yet no age-related differences in the slope or r-values were observed (P > 0.05). Both GM muscle volume (P = 0.003) and PCSA (P = 0.004) exhibited significant age 9 BMI interactions. In addition, muscle volume and PCSA correlated with BMI, body mass and fat mass. Interestingly, ageing reduced both the degree of association in these correlations (P < 0.05) and the slope of the regressions (P < 0.05). Our findings partly support our hypotheses in that obesity-associated changes in GM PCSA and volume differed between the young and old. The younger GM muscle adapted to the loading induced by high levels of body mass, adiposity and BMI by increasing its volume and increasing its pennation angle, ultimately enabling it to produce higher maximum torque. Such an adaptation to increased loading did not occur in the older GM muscle. Nonetheless, the older GM muscle FPA increased to a similar extent to that seen in young GM muscle, an effect which partly explains the relatively enhanced absolute maximum torque observed in obese older females.

Comparison of fat percentage with muscle strength/endurance and blood pressure response in young adults

“…[ [8][9][10] It was also observed in our study that It was reported that in older obese women have a 3-4 times increased risk of developing functional limitations, where their BMI was higher than 30. [11] However, individuals who had Class II sarcopenia had a similar risk of functional limitations as the females who were only characterized as obese.…”

Relationships between Muscle Architecture of Rectus Femoris and Functional Parameters of Knee Motion in Adults with Down Syndrome

“…The pennation angle did not differ from that of TD individuals, and reduced muscle thickness was observed. As previous studies suggest, the changes observed in overweight or obese persons may be considered adaptive changes under the influence of the nervous system [24]. This adaptive mechanism was not observed in participants with DS in our study, possibly due to metabolic or neural maladaptive behavior.…”

“…In young obese girls, excess body mass serves as a chronic training stimulus responsible for an increase in isokinetic muscle strength, showing a positive correlation with an increased pennation angle, muscle thickness, and muscle size [24, 25]. Contrarily, older overweight and obese women were unable to develop a similar adaptive behavior, with the exception of an increased pennation angle [24]. In our study, the majority of participants in the DS group were overweight or obese and a similar adaptation was not found.…”

Effects of resistance training with and without caloric restriction on physical function and mobility in overweight and obese older adults: a randomized controlled trial

“…Obesity is consistently associated with a lower strength-to-mass ratio (muscle quality) in older adults (7,31,32), and a higher muscle lipid content is associated with compromised muscle strength and power (11)(12)(13). The mechanisms by which greater total and intermuscular fat impair muscle function in older adults are not definitively known but could be due to reduced adaptation to increased loading (33), reduced mitochondrial function and capillary density (34)(35)(36)(37), or interference with contractile proteins perhaps secondary to local release and elevated concentrations of fatty acids or cytokines by fat (38)(39)(40)(41).…”