HRV and Blood Parameters for Assessing the Physiological Functioning of Cyclists During Long-Distance Rides Across Different Altitudes

Wipng Du^1,2MIng Zhang¹Xiaodan niu³Hao Li^4*yimin wan^1*

• ¹School of Physical Education, Ningxia Normal University, Guyuan, Ningxia, guyuan, China
• ²Key Laboratory of Brain Cognition and Learning, Ningxia Normal University,, Guyuan, China
• ³Department OF Public Basic Teaching , Xi’an Academy of Fine Arts, Xi’an, Shanxi Province, China
• ⁴School of Physical Education, Shaanxi Normal University, Xi'an, China

Objective: This study aims to systematically investigate the dynamic correlation between the autonomic nervous system and blood adaptiveresponses in cycling athletes during prolonged traverses across varying altitude environments.Methods: Seventeen cycling enthusiasts aged 16–25 years participated in an 8-day altitude cycling challenge. HRV and hematological parameters were measured at three altitudes: 485 m,1627 m, and 4182 m.Results: WBC, HGB, HCT, MCHC, PLT, and PCT) significantly increased at both 1627 m and 4182 m (P < 0.05). HR,SBP, and DBP showed significant elevations at 4182 m (P < 0.05), VC significantly decreased (P < 0.05). SDNN and RMSSD, significantly increased at 1627 m (P < 0.05) but decreased at 4182 m (P < 0.05). VLF, LF and HF, significantly decreased at 4182 m (P < 0.01). SD1 and SD2 significantly decreased at 4182 m (P < 0.01), while ApEn, SampEn, and Alpha2 significantly increased (P < 0.05). At 485 m, SDNN was negatively correlated with HCT (r = –0.55, P < 0.05) and PLT (r = –0.50, P < 0.05), while LF and HF were negatively correlated with HCT (r =–0.55 and –0.54, P < 0.05). At 1627 m, SDNN was positively correlated with MCV (r = 0.53, P < 0.05), LF with MCV (r = 0.23, P < 0.05), and LF/HF was negatively correlated with MCHC (r = –0.52, P < 0.05). At 4182 m, SDNN was positively correlated with MCHC (r = 0.51, P <0.05), VLF was negatively correlated with WBC (r = –0.63, P < 0.05), ApEn was positively correlated with both WBC (r = 0.76, P < 0.05) and HCT (r = 0.62, P < 0.05), and SampEn was positively correlated with WBC (r = 0.74, P < 0.05).Conclusion: The results of this study indicate that at moderate altitude, athletes exhibited a coordinated response of enhanced short-term autonomic adaptation and increased red blood cell volume. At very high altitude, overall HRV decreased while its complexity increased. The altitude-specific correlations between HRV and hematological parameters suggest a potential interaction between autonomic regulation and blood adaptation.