Potentially beneficial effects of cold therapies on training adaptation still remain unequivocal. We have, thus, decided to evaluate the effects of a 2-week volleyball training program supported by 10 sessions of whole body cryostimulation (WBC) on growth factors and physical performance. Twenty healthy college-aged men and women randomly assigned either to the cryostimulation group (CRY) or the control group (CON; executed passive rest). Both groups took part in the same 2-weeks training program. Additionally, the CRY group attended in 10 cryo-sessions (3 min, -110^∘C temperature, five times/week). Blood samples were collected at baseline, 1 h after the first cryo-session as well as before and 1 h after the last session of WBC to assess growth factors, myokines concentration and the amino acid profile. Motor abilities were tested before commencing the training program and 2 days after its completion. The applied intervention resulted in an increase of brain-derived neurotrophic factor and insulin-like growth factor 1 concentrations. The adjusted effect describing the difference between groups in response to applied procedures was for both growth factors large and very likely in the CRY, higher than in the CON group (113%; Coefficient Interval: 38–230%, 45%; Coefficient Interval: 17–79%, respectively). Physical performance dropped in both groups, yet in the CRY group, the magnitude of change was smaller. The fibroblast growth factor dropped significantly 1 h following the first cryo-session, yet irisin remained statistically unchanged. The similar tendency was maintained after the whole procedure, still the range of changes was smaller. In the CRY group, an elevated uptake of tryptophan and valine noted in response to the whole intervention, could have induced a significant decrease of fasting glucose concentration (the adjusted effect small and very likely -6%; Coefficient Interval: -10 to -2%). Overall, a 2-week volleyball training program supported by the whole body cryostimulation protocol resulted in an increase of growth factors and offset a decline of physical performance. Thus these procedure can be applied in professional sport during competition period, especially among those disciplines focusing on an explosive power and ability to concentrate.

The COVID-19 pandemic and subsequent self-isolation exacerbated the problem of insufficient amounts of physical activity and its consequences. At the same time, this revealed the advantage of vitamin D. Thus, there was a need to verify the effects of those forms of training that can be performed independently. In this study, we examined the effects of Nordic walking (NW) and high intensity interval training (HIIT) with regard to the impact of the metabolite vitamin D. We assigned 32 overweight adults (age = 61 ± 12 years) to one of two training groups: NW = 18 and HIIT = 14. Body composition assessment and blood sample collection were conducted before starting the training programs and a day after their completion. NW training induced a significant decrease in myostatin (p = 0.05) concentration; however, the range was dependent on the baseline concentrations of vitamin D metabolites. This drop was accompanied by a significant negative correlation with the decorin concentration. Unexpectedly, NW caused a decrement in both forms of osteocalcin: undercarboxylated (Glu-OC) and carboxylated-type (Gla-OC). The scope of Glu-OC changes was dependent on a baseline concentration of 25(OH)D₂ (r = −0.60, p = 0.01). In contrast, the HIIT protocol did not induce any changes. Overall results revealed that NW diminished the myostatin concentration and that this effect is more pronounced among adults with a sufficient concentration of vitamin D metabolites.

The study aimed to determine whether combining cryostimulation with resistance training would effectively increase muscle strength, and if so, whether this adaptation would be related to changes in circulating levels of exerkines (i.e., mediators of systemic adaptation to exercise). Twenty-five students completed 12 sessions of resistance training, each followed by either cryostimulation (n = 15, 3 min exposure at −110 °C) or passive recovery (n = 10). Prior to and post this intervention, participants performed two eccentric cycling bouts (before and after training). At these points, serum concentrations of muscle damage marker (myoglobin), exerkines (interleukin 6 (IL-6), interleukin 15 (IL-15), irisin, brain-derived neurotrophic factor), hypertrophy-related factors (myostatin, insulin-like growth factor 1), and muscle strength were measured. The applied procedure reduced the physiological burden of the second eccentric cycling bout and myoglobin concentrations only in the group subject to cryostimulation. The same group also exhibited decreased levels of myostatin (from 4.7 ± 1.7 to 3.8 ± 1.8 ng·mL⁻¹, p < 0.05). A significant and large interaction between the group × time was noted in IL-15 concentration (p = 0.01, ${\eta }_p^2=0.27$). Training and cryostimulation induced a positive and likely significant improvement of isokinetic muscle strength. Altogether, obtained results support the claim that resistance training combined with cold exposure modified muscle strength through modulation of myostatin and IL-15 concentrations.

Impaired iron metabolism is associated with increased risk of many morbidities. Exercise was shown to have a beneficial role; however, the mechanism is not well understood. The purpose of this study was to assess the relationship between exerkines and iron metabolism in elderly women before and after 12 weeks of Nordic Walking (NW) training. Exerkines like myostatin, adiponectin, and osteocalcin have been shown to have several positive effects on metabolism. Thirty-six post-menopausal women (66 ± 5 years old, mean ± SD) were randomly assigned to a NW intervention group (n = 18; body mass, 68.8 ± 11.37 kg; fat, 23.43 ± 7.5 kg; free fat mass, 45.37 ± 5.92 kg) or a control group (n = 18; body mass, 68.34 ± 11.81 kg; fat, 23.61 ± 10.03 kg; free fat mass, 44.73 ± 3.9 kg). The training was performed three times a week for 12 weeks, with the intensity adjusted to 70% of the individual maximum ability. Before and one day after the 12-weeks intervention, performance indices were assessed using a senior fitness test. Blood samples (5 mL) were obtained from the participants between 7 and 8 AM, following an overnight fast, at baseline and one day immediately after the 12-week training program. A significant and large time × group interaction was observed for iron (NW: 98.6 ± 26.68 to 76.1 ± 15.31; CON: 100.6 ± 25.37 to 99.1 ± 27.2; p = 0.01; ${\mathsf{\eta }}_{\mathrm{p}}^2$ = 0.21), myostatin (NW: 4.42 ± 1.97 to 3.83 ± 1.52; CON: 4.11 ± 0.95 to 4.84 ± 1.19; p = 0.00; ${\mathsf{\eta }}_{\mathrm{p}}^2$ = 0.62), adiponectin (NW: 12.0 ± 9.46 to 14.6 ± 10.64; CON: 12.8 ± 8.99 to 11.9 ± 8.53; p = 0.00; ${\mathsf{\eta }}_{\mathrm{p}}^2$ = 0.58), and osteocalcin (NW: 38.9 ± 26.04 to 41.6 ± 25.09; CON: 37.1 ± 33.2 to 37.2 ± 32.29; p = 0.03; ${\mathsf{\eta }}_{\mathrm{p}}^2$ = 0.13). Furthermore, we have observed the correlations: basal ferritin levels were inversely correlated with changes in myostatin (r = −0.51, p = 0.05), change in adiponectin, and change in serum iron (r = −0.45, p = 0.05), basal iron, and osteocalcin after training (r = -0.55, p = 0.04). These findings indicate that iron modulates NW training-induced changes in exerkine levels.