Emphasis is usually placed on protein intake – to stave off sarcopenia (muscle loss), but:

Lower Dietary and Circulating Vitamin C in Middle- and Older-Aged Men and Women Are Associated with Lower Estimated Skeletal Muscle Mass, The Journal of Nutrition, October 2020

Conclusions
Our findings of positive associations, of both dietary and circulating vitamin C with measures of skeletal muscle mass in middle- and older-aged men and women, suggest that dietary vitamin C intake may be useful for reducing age-related muscle loss.

Interesting, the bolded part:

Mechanisms
The mechanistic roles for vitamin C in skeletal muscle physiology include the synthesis of carnitine and collagen. These are important because collagen is a key structural component of skeletal muscle cells and tendons, and carnitine is essential for metabolism of long-chain fatty acids during physical activity (14, 15). Animal studies have further elucidated the mechanisms relating to skeletal muscle atrophy, and the morphological changes caused by deficiency of dietary vitamin C. The main drivers appear to be upregulation of the ubiquitin ligases atrogin1/muscle atrophy F-box and muscle RING-finger protein 1 and a reduction in production of ROS (12–15). Moreover, muscle atrophy was reversed by reintroduction of vitamin C into the diet in 1 of these studies (12).

Recall that potatoes are a good source of vitamin C.

Source: Maine Potato Board