The relationship between insulin sensitivity and maximal oxygen uptake is confounded by method of adjustment for body composition.
BACKGROUND
The use of ratios for analyzing physiologic variables often creates spurious associations.


METHODS
Results of a euglycaemic clamp, a graded exercise test to measure maximal oxygen uptake (VO2max) and underwater weighing in 358 nondiabetic adults (166 women and 192 men) were used to compare the effects of weight standardization by division or by partial Spearman correlations on the association between VO2max and insulin sensitivity.


RESULTS
VO2max and insulin sensitivity were negatively correlated when VO2max was divided by weight. When partial Spearman correlations were used to adjust VO2max for body composition, the correlation between VO2max and insulin sensitivity was greatly diminished.


CONCLUSIONS
Division of VO2max by weight does not adjust for weight, but it creates spurious associations between VO2max and insulin sensitivity.
National Institute of Diabetes and Digestive and Kidney Diseases, Phoenix, AZ, USA.
Brian A
BA
Grice
Clinton C
CC
Mason
E Jennifer
EJ
Weil
William C
WC
Knowler
Jeremy
J
Pomeroy
D050154:Adiposity; D000328:Adult; D000886:Anthropometry; D001823:Body Composition; D001835:Body Weight; D005080:Exercise Test; D005260:Female; D015309:Glucose Clamp Technique; D006801:Humans; D007328:Insulin / Q000008:administration & dosage / Q000378:metabolism*; D008176:Lung Volume Measurements; D008297:Male; D018482:Muscle, Skeletal / Q000378:metabolism*; D010101:Oxygen Consumption; D011237:Predictive Value of Tests; D012016:Reference Values; D015203:Reproducibility of Results; D055815:Young Adult
D007328:Insulin
VO2max; insulin sensitivity; maximal oxygen uptake; per-weight standard; ratio adjustment