Effect of hypoxia, safety shoe type, and lifting frequency on cardiovascular and ventilation responses

Objective: There is limited work on the physiological demands of lifting activities at different altitudes and different lifting frequencies when wearing different types of shoes. This study aimed to examine the heart rate variability (HRV) and ventilation responses of individuals in normobaric hypoxia (ambient oxygen of 15%, 18%, and 21%) while doing lifting tasks and wearing three types of different safety shoes (light, medium, and heavy-duty) at two different lifting frequencies (1 lift/min and 4 lifts/min). Methods: Using an experimental study design, two sessions were conducted by ten male university students that included an acclimatization and training session followed by experimental lifting. The study used a four-way repeated measures design (4 independent and twenty-one responses, i.e., twelve HRV and nine ventilation responses). Results: The findings highlighted substantial low HRV and ventilation parameters for the light workload stress in the form of higher ambient oxygen content and lowered lifting frequency while wearing light safety shoe type. It also presented an increase in the physical demand, followed by increased lifting frequency and replication with increased mean heart rate and decreased mean RR, very low frequency (VLF) power, low frequency (LF) power, and low frequency to a high-frequency ratio (LF/HF). Conclusion: Our findings suggest that if a safe lifting load limit is applied for workers in the industrial environment, the risk of musculoskeletal disorders will be mainly decreased, and the rate of production will be better with ambient oxygen content and appropriate safety shoes. This research would safeguard industrial workers' physical capacities and future health risks.