Table 1.

Characteristics of the subjects enrolled in the present study

	Aim	Subjects	Protocol
Group A	To test the reproducibility of measured muscle perfusion	10 healthy volunteers, 4 men and 6 women, 29.4 (SD 6.4) yr old	Repeated 8 lb on 2 separate days
Group B	To investigate the relationship between exercise intensity and muscle perfusion	8 healthy volunteers, 6 men and 2 women, 26.0 (SD 4.6) yr old	Exercise with loads of 4, 8, and 16 lb
Group C	A pilot study to test the feasibility of a dual-intensity protocol for assessing PAD	5 elderly healthy volunteers, 4 men and 1 woman, 62.6 (SD 4.3) yr old, BMI 28.4 (SD 3.5);	4 lb and exercise to exhaustion on a same day
		5 patients with PAD, 4 men and 1 woman, 61.2 (SD 4.8) yr old, ABI 0.73 (SD 0.10), BMI 25.2 (SD 5.5)

Plantar flexion with a load of 4 lb and frequency of 1 Hz in our experiments corresponds to a work output of ~2.7 W. PAD, peripheral artery disease; BMI, body mass index; ABI, ankle-brachial index.