Table 1.
Baseline characteristics of study participants
| Characteristic | Trained (n = 29) | Sedentary (n = 28) | P Value |
|---|---|---|---|
| Female/Male | 13/16 | 13/15 | 0.90 |
| Age, yr | 25.9 (0.9) | 22.6 (0.6) | <0.01 |
| Body mass index, kg/m2 | 22.1 (0.4) | 22.3 (0.4) | 0.72 |
| V̇o2max | |||
| Absolute treadmill V̇o2max, ml/min (Minnesota) | 2,601.8 (217.1) | 1,730.7 (108.5) | <0.01 |
| Treadmill V̇o2max, ml·kg FFM−1·min−1 (Minnesota) | 61.6 (1.4) | 55.8 (1.6) | 0.01 |
| Absolute cycling V̇o2max, ml/min (Pittsburgh) | 3,815.7 (290.7) | 2,640.5 (192.6) | <0.01 |
| Cycling V̇o2max, ml·kg FFM−1·min−1 (Pittsburgh) | 70.7 (2.3) | 52.6 (1.8) | <0.01 |
| Free fatty acid levels | |||
| Baseline, μM | 386 (55) | 430 (38) | 0.51 |
| End of lipid infusion, μM | 489 (44) | 641 (62) | 0.05 |
| Insulin sensitivity | |||
| Glucose infusion rate, mg glucose infused·kg FFM−1·min−1 at the end of a 3 h clamp (Minnesota) | 12.2 (0.8) | 9.1 (0.6) | <0.01 |
| Glucose infusion rate, mg glucose infused·kg FFM−1·min−1 at the end of a 6 h clamp (Pittsburgh) | 13.4 (0.5) | 10.7 (1.0) | 0.02 |
| Muscle fiber type | |||
| Type 1 fibers, % | 47.5 (3.6) | 36.5 (2.0) | 0.01 |
| Type 2 fibers, % | 52.4 (3.6) | 63.5 (2.0) | 0.01 |
| Type 2a fibers, % | 44.3 (3.0) | 43.4 (1.5) | 0.80 |
| Type 2x fibers, % | 9.0 (2.3) | 20 (2.0) | <0.01 |
| Fiber type-specific lipid staining (LAI) | |||
| % of type 1 fibers, au | 38.3 (3.3)* | 51.3 (4.0)* | 0.01 |
| % of type 2 fibers, au | 29.4 (2.2) | 28.8 (2.9) | 0.88 |
| % of type 2a fibers, au | 29.7 (2.1) | 28.6 (2.4) | 0.72 |
| % of type 2x fibers, au | 28.1 (3.6) | 31.8 (0.1) | 0.60 |
| Fiber type specific lipid staining, considering fiber type distribution within sample (Adjusted LAI) | |||
| % of type 1 fibers, au | 18.5 (2.3)* | 18.6 (2.0)* | 0.97 |
| % of type 2 fibers, au | 13.0 (1.0) | 15 (1.6) | 0.28 |
| % of type 2a fibers, au | 12.0 (1.1) | 13.0 (1.4) | 0.59 |
| % of type 2x fibers, au | 1.6 (0.2) | 5.7 (1.0) | <0.01 |
| Total IMCL in muscle (adjusted LAI type 1 fibers + adjusted LAI type 2 fibers) | 31.4 (2.4) | 30.9 (2.4) | 0.89 |
Results are reported as means (±SE) if a continuous variable; 57 participants were available for analysis. These were derived from the University of Minnesota (n = 31, n = 15 trained) and University of Pittsburgh (n = 26, n = 14 trained). FFA, free fatty acids; FFM, fat-free mass; LAI, % area stained by lipid. LAI = 100 × (area stained within specific fiber type/total area of specific fiber type). Adjusted LAI = 100 × (area stained within specific fiber type/total muscle fiber area).
*
Significant difference (P < 0.05) compared with other fiber types within same training status.