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Obesity is a global epidemic and coupled with the unprecedented growth of the world’s older adult population, a growing number of individuals are both old and obese. Whilst both ageing and obesity are associated with an increased prevalence of chronic health conditions and a substantial economic burden, evidence suggests that the coincident effects exacerbate negative health out-comes. A significant contributor to such detrimental effects may be the reduction in the contractile performance of skeletal muscle, given that poor muscle function is related to chronic disease, poor quality of life and all-cause mortality. Whilst the effects of ageing and obesity independently on skeletal muscle function have been investigated, the combined effects are yet to be thoroughly explored. Given the importance of skeletal muscle to whole-body health and physical function, the present study sought to provide a review of the literature to: (1) summarise the effect of obesity on the age-induced reduction in skeletal muscle contractile function; (2) understand whether obesity effects on skeletal muscle are similar in young and old muscle; (3) consider the consequences of these changes to whole-body functional performance; (4) outline important future work along with the potential for targeted intervention strategies to mitigate potential detrimental effects.

Prolonged high-fat diets (HFD) can cause intramyocellular lipids (IMCL) accumulation that may negatively affect muscle function. We investigated the duration of a HFD required to instigate these changes, and whether effects are muscle-specific and aggravated in older age. Muscle morphology was determined in the soleus, extensor digitorum longus (EDL) and diaphragm muscles from female CD-1 mice divided into 5 groups: young fed a HFD for 8 weeks (YS-HFD, n=16), young fed a HFD for 16 weeks (YL-HFD, n=28) and young control (Y-CON, n=28). The young animals were 20 weeks old at the end of the experiment. Sixty 70-week-old female CD-1 mice received either a normal diet (O-CON, n=30) or a HFD for 9 weeks (OS-HFD, n=30). Body mass, body mass index and IMCL content increased in old OS-HFD (p≤0.003). In the young mice, this increase was seen in YL-HFD and not YS-HFD (p≤0.006). The soleus and diaphragm fibre cross-sectional area (FCSA) in YL-HFD was larger compared to Y-CON (p≤0.004) while old mice had a larger soleus FCSA compared to CON after only 9 weeks on a HFD (p<0.001). The FCSA of the EDL muscle did not differ significantly between groups. Oxidative capacity of fibres increased in young only, irrespective of HFD duration (p<0.001). High-fat diet-induced morphological changes occur earlier in the old animals when compared to young, and adaptations to HFD are muscle-specific with the EDL being least responsive.

© 2019 Elsevier Inc. One of the hallmarks of ageing is muscle wasting that may be preceded by morphological changes, such as capillary rarefaction. Muscle-specific changes in morphology in early ageing may differ between locomotor and respiratory muscles. To investigate this, we compared capillarization, fiber type composition, fiber cross-sectional area (FCSA) and oxidative capacity of individual fibers of the soleus (n = 6/5 for 20- and 79 weeks, respectively), extensor digitorum longus (EDL: n = 3/3) and diaphragm (n = 7/5) muscles in 20- (mature) and 79-week-old (early ageing) CD-1 female mice. There was no significant loss of soleus and EDL mass. The FCSA was larger and the capillary density lower at 79 than 20 weeks in the diaphragm, while in the EDL the opposite was found (both p ≤ 0.002) with no significant ageing-related differences in the soleus. The heterogeneity in capillary spacing, which may negatively impact on muscle oxygenation, was highest in muscles from 20-week-old mice, irrespective of muscle (p ≤ 0.011). Succinate dehydrogenase activity, indicative of oxidative capacity, and capillary to fiber ratio did not significantly change with age in any muscle. At all ages, the capillary supply to a fiber was positively related to FCSA in each muscle. We conclude that despite previously reported early age-related reductions in specific tension in both locomotor and respiratory muscles, morphological changes show a muscle-specific pattern in early ageing CD-1 mice. Specifically, early ageing was associated with 1) diaphragm hypertrophy 2) and fiber atrophy in the EDL that was not accompanied by angiogenesis, capillary rarefaction or reductions in oxidative capacity.

© 2014 European College of Sport Science. The aim of this study was to investigate if the effects of changes in physiological arousal on timing performance can be accurately predicted by the catastrophe model. Eighteen young adults (8 males, 10 females) volunteered to participate in the study following ethical approval. After familiarisation, coincidence anticipation was measured using the Bassin Anticipation Timer under four incremental exercise conditions: Increasing exercise intensity and low cognitive anxiety, increasing exercise intensity and high cognitive anxiety, decreasing exercise intensity and low cognitive anxiety and decreasing exercise intensity and high cognitive anxiety. Incremental exercise was performed on a treadmill at intensities of 30%, 50%, 70% and 90% heart rate reserve (HRR) respectively. Ratings of cognitive anxiety were taken at each intensity using the Mental Readiness Form 3 (MRF3) followed by performance of coincidence anticipation trials at speeds of 3 and 8 mph. Results indicated significant condition × intensity interactions for absolute error (AE; p =.0001) and MRF cognitive anxiety intensity scores (p =.05). Post hoc analysis indicated that there were no statistically significant differences in AE across exercise intensities in low–cognitive anxiety conditions. In high–cognitive anxiety conditions, timing performance AE was significantly poorer and cognitive anxiety higher at 90% HRR, compared to the other exercise intensities. There was no difference in timing responses at 90% HRR during competitive trials, irrespective of whether exercise intensity was increasing or decreasing. This study suggests that anticipation timing performance is negatively affected when physiological arousal and cognitive anxiety are high.