Physiological and biochemical responses during incremental uphill load carriage

• Uphill load carriage stress was assessed by biochemical, physiological responses.
• Increased load, speed and grade lead to significant increase in salivary cortisol.
• Similar conditions caused significant decrease in sIgA concentration.
• Physiological responses increased with increased exercise intensity.
• Data can be used to design military training schedules and reduce URTI.

The present study aimed to examine the effect of carrying different magnitudes of load on the changes and relationships of salivary Immunoglobulin A (IgA) and cortisol concentrations and the physiological parameters. Twelve Indian soldiers performed an intense uphill treadmill walking at two speeds viz. 2.5 km h−1 and 4 km h−1 without any load and carrying 10.7 kg, 17 kg and 21.4 kg loads for 36 min. Salivary IgA concentration relative to total protein decreased significantly after each exercise session and cortisol concentration increased concomitantly with physiological variables e.g. heart rate (HR), oxygen consumption (VO2), minute ventilation (VE) and energy expenditure (EE). An inverse correlation (P < 0.05) was observed between IgA with HR for all the conditions except when the participants walked at 4 km h−1 carrying 17 kg and 21.4 kg load. The degree and type of physiological and biochemical responses may help in designing combat training, operations and developing preventive strategies of military personnel involving intense exercise.Relevance to industry: Walking with load in incremental uphill terrain is highly stressful and fatiguing. Results of the present study will help in designing training schedules for maintaining the optimal fitness of an individual during uphill walking with loads in different speeds.