Table 1.

Muscle free phenylalanine/leucine labeling in the final biopsy, the change in muscle protein bound phenylalanine/leucine labeling over time, and the duration between two biopsies or the time lapse from beginning the tracer infusion and the final biopsy for the single-biopsy approach

	Two Biopsies		Single Biopsy
	0 min and 210 min	60 min and 240 min	“Zero” background	Population average background
[ring-2H5]phenylalanine
Muscle free TTR	0.0639 ± 0.0037	0.0642 ± 0.0078	0.0640 ± 0.0043	0.0640 ± 0.0043
Time for FSR calculation, min	224 ± 4	171 ± 3	229 ± 3	229 ± 3
ΔMuscle protein TTR	0.000119 ± 0.000022	0.000094 ± 0.000022	0.000147 ± 0.000021	0.000129 ± 0.000021
[5,5,5-2H3]leucine
Muscle free TTR	0.0327 ± 0.0020	0.0530 ± 0.0078	0.0419 ± 0.0047	0.0419 ± 0.0047
Time for FSR calculation, min	218 ± 3	177 ± 4	227 ± 4	227 ± 4
ΔMuscle protein TTR	0.000046 ± 0.000005	0.000056 ± 0.000008	0.000107 ± 0.000023	0.000051 ± 0.000023

Values are means ± SE. TTR, tracer-to-tracee ratio; FSR, fractional synthesis rate.