Table 1.

Summary of cross-sectional studies of changing skeletal muscle mass, comparing those in age groups considered to represent “peak muscle mass” versus elderly.

Study	Technique	Estimate	Sex	Young (years)	Aged (years)	n	Change	% Change	% Change/year
Novak (1972)	Total body potassium	Fat free mass	M	18–25	65–85	27, 18	−13 kg	−22	−0.44
		Cell mass					−7.3 kg	−22	−0.44
		Fat free mass	F			89, 13	−3.0 kg	−8.0	−0.16
		Cell mass					−1.7 kg	−8.0	−0.16
Tzankoff and Norris (1977)	24 h urinary creatinine excretion	Muscle mass	M	20	90	14, 12	−965 mg/24 h	−49	−0.7
				20	80	14, 103	−745mg/24 h	−38	−0.63
Cohn et al. (1980)	Total body nitrogen (Prompt gamma neutron-activation technique)	Fat free mass	M	20–29	70–79	24, 9	−9.0 kg	−14	−0.28
		SMM					−10.9 kg	−45	−0.9
		Fat free mass	F	20–29	70–79	10, 8	−7.8 kg	−18	−0.36
		SMM					−4.0 kg	−40	−0.8
Borkan et al. (1983)	Computed tomography scan	Upper leg muscle CSA	M	46.3 ± 2.6	69.4 ± 4.1	21, 20	−18.2 cm2	−12	−0.52
		Upper arm muscle CSA					−6.4 cm2	−11	−0.48
	Total body potassium	Fat free mass					−6.6 kg	−11	−0.48
Lexell et al. (1983)	Cadaveric dissection	Vastus lateralis CSA	M	30 ± 6	72 ± 2	6, 6	−576 mm2	−17.6	−0.42
Young et al. (1985)	Ultrasound scan	CSA of quadriceps muscles (mid-thigh)	M	20–30	70–80	12, 12		−25	−0.5
Lexell et al. (1988)	Cadaveric dissection	Vastus lateralis CSA	M	19 ± 3	73 ± 2	9, 9	−960 mm2	−26	−0.48
				19 ± 3	82 ± 1	9, 8	−1584 mm2	−43	−0.68
Janssen et al. (2000)	Magnetic resonance imaging	SMM	M	18–29	>70	66, 11	−5.9 kg	−18	−0.36
		Lower body SMM					−4.7 kg	−25	−0.5
		Upper body SMM					−0.8 kg	−5.6	−0.11
		SMM	F	18–29	>70	40, 19	−3.8 kg	−17	−0.34
		Lower body SMM					−2.8 kg	−22	−0.44
		Upper body SMM					−1.0 kg	−11	−0.22
Kyle et al. (2001)	Dual-energy X-ray absorptiometry	ASMM	M	18–34	>80	68, 26	−5.4 kg	−19.9%	−3.3
			F	18–34	>80	40, 30	−2.6 kg	−14.1%	−2.3
Silva et al. (2009)	Dual-energy X-ray absorptiometry	SMM	M	18–80 mean 40 ± 14.4		468	−1.58 kg/decade after 27	N/A	−0.46
			F	18–80 mean 44.5 ± 15.9		1280	−0.81 kg/decade after 27	N/A	−0.46
Wroblewski et al. (2011)	Air displacement plethysmography and MRI in high-level recreational athletes	SMM	M	44.8 ± 3.2	65.4 ± 2.2	5, 5	−4.1 kg	−6.7	−0.32
				44.8 ± 3.2	76.3 ± 3.3	5, 5	−7.3 kg	−12	−0.38
			F	47.0 ± 2.8	65.0 ± 3.0	5, 5	−4.3 kg	−9.8	−0.54
				47.0 ± 2.8	74.8 ± 3.7	5, 5	−7.0 kg	−16	−0.57