Exercise efficiency during arm ergometry: effects of speed and work rate.

Area of Science:

• Exercise Physiology
• Biomechanics
• Human Performance

Background:

• Understanding exercise efficiency is crucial for optimizing training and performance.
• Arm crank ergometry (ACE) is a valuable tool for assessing upper body exercise capacity.
• The interplay between work rate, movement speed, and efficiency in ACE requires further investigation.

Purpose of the Study:

• To investigate the impact of increasing work rate and movement speed on efficiency during steady-state ACE.
• To quantify gross, work, and delta efficiencies across various power outputs and rotational speeds.
• To determine the independent and combined effects of power output and speed on ACE efficiency.

Main Methods:

• Ten healthy men performed ACE at speeds of 50, 70, and 90 rpm and power outputs of 15, 30, 45, and 60 W.
• Oxygen uptake was measured via open-circuit spirometry, and energy expenditure was calculated using the respiratory exchange ratio.
• Gross, work, and delta efficiencies were computed based on work accomplished and energy expended.

Main Results:

• A curvilinear relationship between work rate and energy expenditure was observed.
• Work and delta efficiencies decreased with increasing power output (work: 20-29%, delta: 14-30%).
• Gross efficiency increased with power output (6-15%) due to the reduced influence of resting metabolic rate, but decreased at higher speeds (90 rpm vs. 50/70 rpm).

Conclusions:

• Both delta and work efficiencies in ACE are diminished by increases in speed or power output.
• Gross efficiency demonstrates a dual response: increasing with power output but decreasing with movement speed.
• These findings highlight the importance of considering both intensity and velocity when evaluating ACE performance and efficiency.