Estimating metabolic rate from ISO heart rate method and two walking equations

Area of Science:

• Occupational health and safety
• Human physiology
• Environmental stress assessment

Background:

• Accurate metabolic rate estimation is crucial for heat stress assessment.
• Existing methods include the ISO 8996 standard (ACSM and heart rate methods) and the US Army's Load Carriage Decision Aid (LCDA).

Purpose of the Study:

• To evaluate the accuracy and precision of the ISO heart rate method compared to ACSM and LCDA predictive equations for metabolic rate.
• To inform best practices for heat stress assessment in occupational settings.

Main Methods:

• Utilized a laboratory database from a progressive heat stress protocol.
• Measured metabolic rate, heart rate, treadmill speed, and grade.
• Assessed accuracy and precision using Bland-Altman plots and Root Mean Square Error (RMSE).

Main Results:

• All three methods demonstrated good accuracy with low bias.
• The ISO heart rate method had a higher RMSE (34 W, 11%) for precision compared to the ACSM and LCDA equations (20 W, 7%).
• The heart rate method, despite lower precision, offers greater generalizability.

Conclusions:

• The ISO heart rate method is less precise but more broadly applicable for metabolic rate estimation in heat stress assessment.
• Recommend using the heart rate method below occupational exposure limits to mitigate bias from heat strain.
• Further research may refine predictive models for diverse occupational scenarios.