Fuel selection in shivering humans.
Level 5 - mechanism / opinion, no new human data
Narrative review of human physiological mechanisms and metabolic fuel utilization without systematic review methodology.
PubMed 16026423 · doi:10.1111/j.1365-201X.2005.01465.x
What was done
This narrative review synthesized evidence on oxidative fuel selection and thermogenic substrate utilization (lipids, plasma glucose, and muscle glycogen) alongside muscle fiber recruitment patterns in humans exposed to cold stress.
What was found
The abstract reports qualitative physiological directions without specific numerical values. Lipids provide the majority of heat during low-intensity shivering, whereas carbohydrate oxidation dominates under severe cold conditions. The relative contribution of circulating plasma glucose remains minor, while muscle glycogen serves as an essential fuel during intense shivering. Additionally, shivering relies on two distinct fuel-selection mechanisms compared to exercise: shifting metabolic pathways within the same muscle fibers and activating specific fuel-specialized fiber types across the muscle.
Why it matters
Understanding the metabolic shift toward muscle glycogen during intense shivering outlines how individual variations in muscle fiber composition and energy stores may dictate human survival and thermoregulatory limits in cold environments.
Limits
The abstract provides no quantitative data, sample sizes, or formal systematic review methodology. It explicitly highlights gaps in the literature, noting that whether muscle glycogen store capacity directly affects cold endurance remains unproven and the mechanisms driving differences between exercise and shivering metabolism remain uninvestigated.
Cited by
- contradicts Shivering burns carbohydrate as fuel rather than fat.