One study examined the effect of vitamin C supplementation on injury rate as well as on performance. Gey et al. (1970) placed 286 U.S. Air Force officers into two groups: officers in one group received 1000 mg vitamin C and officers in the other received a placebo daily for 12 weeks during moderate training. After 12 weeks, the groups showed no differences in improvement of performance on the Cooper 12-minute walk-run test (Gey et al., 1970). Also, the group taking vitamin C supplements had no reduction in injury rate compared with the group without supplementation.

Vitamin C also acts as an antioxidant to protect cells from free radical damage (see vitamin E section) (Machlin and Bendich, 1987). Because muscle soreness after exercise may result from muscle tissue damage (Ebbeling and Clarkson, 1989), it could be hypothesized that vitamin C supplementation may affect the development of soreness. Staton (1952) examined whether vitamin supplementation of 100 mg per day for 30 days would affect the performance of sit-ups on the second day of performance of the sit-ups (assuming that subjects were sore from the first day of sit-ups). The number of fewer repetitions the subjects were able to perform on the second day was taken to indicate the amount of soreness experienced. Vitamin C did not affect the number of sit-ups that could be performed, and Staton (1952) concluded that vitamin C had no effect on soreness. Whether the criterion score reflected an individual's soreness is uncertain. Also, because the exercise used in this study may not have produced significant muscle damage, especially with regard to the generation of free radicals, further study of the relationship of vitamin C and exercise-induced muscle damage is warranted.

In 1942, Holmes reviewed the use of vitamin C during World War II. He stated that "under certain severe conditions soldiers may need dietary supplements of certain vitamins. This is especially true of vitamin C, ascorbic acid, of which the United States used 17 tons in 1940 and may soon reach an annual output (synthetic) of 100 tons." Although Holmes provides citations to support the loss of vitamin C in appreciable quantities in sweat, this claim has not been substantiated by other studies. For example, one study found that at a sweat secretion of 700 ml per hour or more, the loss in vitamin C would not exceed 3 mg per day (Mitchell and Edman, 1951). However, Holmes stated that "the function of the vitamin C may go beyond mere replacement of the amount lost. It may combat heat shock." He also suggested that vitamin C may play a role in the healing of fractures and other wounds.

An interesting letter (Poda, 1979) regarding vitamin C intake and heat stroke appeared in a medical journal in 1979 and is excerpted below: