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Background Cancer cachexia is a multifactorial wasting syndrome that is characterized by the loss of skeletal muscle mass and weakness, which compromises physical function, reduces quality of life, and ultimately can lead to mortality. Experimental models of cancer cachexia have recapitulated this skeletal muscle atrophy and consequent decline in muscle force‐generating capacity. We address these issues in a novel transgenic mouse model Kras, Trp53, and Pdx‐1‐Cre (KPC) of pancreatic ductal adenocarcinoma using multi‐parametric magnetic resonance measures. Methods KPC mice (n = 10) were divided equally into two groups (n = 5 per group) depending on the size of the tumour, that is, tumour size 250 mm3. Using multi‐parametric magnetic resonance measures, we demonstrated the changes in the gastrocnemius muscle at the microstructural level. In addition, we evaluated skeletal muscle contractile function in KPC mice using an in vivo approach. Results Increase in tumour size resulted in decrease in gastrocnemius maximum cross‐sectional area, decrease in T2 relaxation time, increase in magnetization transfer ratio, decrease in mean diffusivity, and decrease in radial diffusivity of water across the muscle fibres. Finally, we detected significant decrease in absolute and specific force production of gastrocnemius muscle with increase in tumour size. Conclusions Our findings indicate that increase in tumour size may cause alterations in structural and functional parameters of skeletal muscles and that MR parameters may be used as sensitive biomarkers to non‐invasively detect structural changes in cachectic muscles.

Background Advanced magnetic resonance imaging (MRI) is capable of identifying subtle effects of exercise. However, it is unclear whether it is sensitive enough to differentiate between different contractions. Purpose To compare the acute and delayed effects of concentric and eccentric exercise on quantitative MRI in hamstring muscles. Material and Methods Participants performed eccentric and concentric leg curls. Quantitative T2 and magnetization transfer ratio (MTR) maps were calculated in the hamstring complex before exercise, 30 minutes, 24 hours, 7 days, and 14 days after exercise. Results Compared to baseline, significant MTR reduction (-7.3%) and T2 elevation (72.2%) were observed in the semitendinosus muscle (ST) at 24 hours after eccentric exercise ( P = 0.04). Concentric contractions induced T2 elevation in the ST (20.8%) and biceps femoris (5.1%) muscles at 30 minutes after exercise ( P = 0.04) which normalized within 24 hours. Conclusions Longitudinal effects of concentric and eccentric exercise can be detected by both T2 and MTR, but T2 is more sensitive to subtle alterations.