Maximal Fat Oxidation during Incremental Upper and Lower Body Exercise in Healthy Young Males

Area of Science:

• Exercise Physiology
• Metabolic Adaptations
• Sports Science

Background:

• Maximal fat oxidation (MFO) is a key metric for understanding fuel utilization during exercise.
• Previous research has primarily focused on lower body exercise, leaving upper body exercise MFO less understood.
• Individual responses to exercise intensity and fuel metabolism vary significantly.

Purpose of the Study:

• To determine and compare the magnitude of maximal fat oxidation (MFO) during incremental upper body (arm cranking exercise, ACE) and lower body (cycle ergometry, CE) exercise.
• To identify the exercise intensities at which MFO occurs for both ACE and CE.
• To investigate the variability in MFO between participants for different exercise modalities.

Main Methods:

• Thirteen untrained males completed two incremental ACE and CE tests to exhaustion.
• Expired gases were analyzed to calculate fat and carbohydrate oxidation rates at each exercise stage.
• MFO was identified as the highest fat oxidation rate during incremental exercise, relative to peak oxygen uptake (%V˙O_2peak).

Main Results:

• MFO was significantly lower during ACE (0.44 g·min^-1) compared to CE (0.77 g·min^-1).
• The intensity at which MFO occurred was also lower during ACE (53%V˙O_2peak) versus CE (67%V˙O_2peak).
• Inter-participant variability in MFO was notably higher during ACE.

Conclusions:

• Upper body exercise elicits a lower MFO compared to lower body exercise.
• Exercise intensity prescription for optimizing fat loss should consider the modality of exercise, with lower intensities recommended for upper body activities.
• These findings have implications for designing effective exercise interventions for weight management.