Background: Nordic walking is a form of physical activity recommended for people of all ages and it is used in disease prevention and health promotion. The study was aimed to determine if and in what ways a six-week Nordic walking training program in late autumn may affect 25(OH)D concentration in postmenopausal overweight women.
Methods: Two series of measurements were carried out in a group of 17 women aged 57±4.20 years with low physical activity level. The first series encompassed a 6-week Nordic walking training program at the intensity of 60-70% VO2max. Before and after the training program body composition was determined with a densitometer, and biochemical indices were measured in blood samples drawn at rest. After a year a second series of measurements at rest was carried out to determine whether changes in the vitamin D (25(OH)D) blood level were season-induced or modified by physical activity.
Results: The Nordic walking training program contributed to a significant reduction of body mass, percentage fat volume and BMI in the examined women. The mean 25(OH)D concentration in the examined women significantly decreased after 6 weeks of training. No similar vitamin D level changes were observed in the II measurement series.
Conclusions: A six-week Nordic walking training program in late autumn contributed to the lowering of 25(OH)D blood concentration in women after 55 years of age. The decreased 25(OH)D concentration may have been a result of reduced dermal biosynthesis of vitamin D or due to vitamin D contribution to muscle metabolism. This is an indication that vitamin D3 supplementation should be recommended in periods of intense physical activity during months with little insolation, especially to overweight postmenopausal women.