Table 4.

Amount of energy available from endogenous and exogenous energy sources.

Type	Energy source	Available energy	References
Mechanical	Heartbeat	0.93 W	[104]
	Blood flow	50–150 cm s−1	[230]
	Breathing	0.41 W	[104]
	GI motility	Table 8
	Center of mass	20 W	[104]
	Shoulder	2.2 W	[104]
	Knee	36.4 W	[104]
	Ankle	66.8 W	[104]
	Heel strike	20 W	[104]
Chemical	Blood glucose	4.5 × 10−3–10 × 10−3 M	[231]
	CSF glucose	4 × 10−3–25 × 10−3 M	[232-234]
	GI pH	pH 1–8	[235]
	GI nutrients	Table 10	.
Electromagnetic	EM wave	10 mW cm−2	[236]
	Ultrasound	Average 10–1000 mW cm−2, max pulse 190 W cm−2	[237]
Bioelectric	Endocochlear potential	70–100 mV	[223]