Physiological and biomechanical responses during treadmill walking with graded loads

Area of Science:

• Exercise Physiology
• Human Biomechanics
• Cardiovascular Health

Background:

• Load carriage is a common activity with potential cardiovascular implications.
• Understanding the physiological responses to varying loads is crucial for safety and performance.
• Previous research suggests a dose-response relationship between load and cardiovascular stress.

Purpose of the Study:

• To investigate the cardiovascular responses to carrying different loads during treadmill walking.
• To determine if increasing load from 15 kg to 20 kg significantly alters physiological stress.
• To compare cardiovascular responses between unloaded and loaded walking conditions.

Main Methods:

• Eleven healthy men performed treadmill walking tests at self-selected velocity.
• Participants carried loads of 15 kg and 20 kg in front of their body.
• Measurements included oxygen uptake (VO2), heart rate (HR), cardiac output (Qc), and blood pressure (BP).

Main Results:

• Significant increases in VO2, HR, Qc, and mean BP were observed during both 15 kg and 20 kg load carriage compared to unloaded walking.
• Stroke volume (SV), arterio-venous oxygen difference (C(a-v)O2), rate pressure product (RPP), and total peripheral resistance (TPR) remained unchanged.
• No significant differences in cardiovascular responses were found between the 15 kg and 20 kg loads, despite higher VO2 at 20 kg.

Conclusions:

• Increasing load from 15 kg to 20 kg during treadmill walking does not significantly increase cardiovascular stress in healthy subjects.
• The cardiovascular system may not respond linearly to increasing loads beyond a certain threshold.
• These findings suggest that the cardiovascular system adapts to moderate increases in load carriage without a proportional rise in stress.