Introduction: Multiple myeloma (MM) is a hematological malignancy affecting older adults. One of the most common myeloma-defining events is the development of symptomatic lytic bone disease. The serum concentrations of calcium (Ca), inorganic phosphorus (P), and vitamin 25(OH)D3 in the serum reflect bone metabolism. An enzyme lactate dehydrogenase (LDH) is a marker of muscle damage, but its serum activity also has an important prognostic value in MM. Myoglobin (Mb) is a small protein present in muscles; its serum level increases when myocytes are damaged. Objectives: In this study, the impact of a 6-week Nordic walking (NW) exercise program on blood parameters related to calcium-phosphate metabolism and damage of skeletal muscles was assessed. Patients and methods: A total of 33 patients with MM in the remission stage, without cytostatic treatment, were allocated and randomly assigned to one of two groups: 17 in the training group (NW) and 16 in the control group (CG). All patients were supplemented per os with vitamin D3 and calcium carbonate daily and received zoledronic acid every 4 weeks (intravenous). Nordic walking training sessions took place 3 times a week for 6 weeks, 1 h each. Blood samples were drawn before and after the 6 weeks of training sessions to assess the serum concentrations of vitamin 25(OH)D3, P, Ca, Mb, and LDH. Results: Patients from the NW group showed a statistically significant decrease in mean serum myoglobin concentration (p = 0.018) and an increase in 25(OH)D3 (p < 0.001) and total Ca (p = 0.001) concentrations. There were no statistically significant changes in the results obtained in CG. Between groups, after 6 weeks, Mb serum concentration was significantly lower in NW (p = 0.041), and 25(OH)D3 was higher (p < 0.001) compared to CG. There was a correlation between the changes in myoglobin, phosphorus, 25(OH)D3, and Ca concentrations after 6 weeks. Conclusions: NW training is a safe and beneficial form of physical exercise for patients with MM without inducing muscle damage. NW performed outside improves serum vitamin 25(OH)D3 concentration.
Keywords: calcium-phosphate metabolism; multiple myeloma; muscle damage; physical activity; vitamin D.