Table 3.

Response of Hind-Limb Muscles in Young and Old Rats to HU and Reloading

	Age		Control	HU	% Loss	HU/REL
Body weight	9	Pre	410 ± 86	400 ± 15		418 ± 20
		Post	436 ± 23	353 ± 21		367 ± 25
	30	Pre	549 ± 32	565 ± 10		592 ± 42
		Post	552 ± 34	471 ± 11		479 ± 37
Soleus	9		166 ± 10	99 ± 3*	42%	146 ± 15†
	30		161 ± 13	104 ± 10*	34%	142 ± 15
						p = .06†
Plantaris	9		438 ± 23	325 ± 19*	25%	422 ± 21†
	30		355 ± 31	274 ± 22*	22%	314 ± 27
						p = .02†
Medial gastrocnemius	9		978 ± 16	666 ± 43*	32%	887 ± 51
						p = .02†
	30		754 ± 37	510 ± 57*	30%	612 ± 42*†
Tibialis anterior	9		826 ± 34	665 ± 54*	19%	813 ± 69†
	30		684 ± 60	593 ± 26*	14%	597 ± 43*†
Extensor digitorum longus	9		193 ± 13	162 ± 9*	13%	187 ± 12†
	30		176 ± 18	149 ± 15*	14%	150 ± 17*†

Notes: Body weights (g) and muscle wet weights (mg) taken from male Fisher 344–Brown Norway F1 hybrid rats aged 9 and 30 mos subjected to 14 days of hind-limb unloading (HU) alone or 14 days of HU followed by 14 days of hind-limb reloading (HU/REL). The mean body weights are given for each experimental group both before (pre) and after (post) the HU period. For the control group, rats were maintained in standard rat cages for 14 days during the HU period. The percent muscle loss (% loss) is the average loss of wet weight due to the HU, calculated as a % relative to control. Data are mean ± standard deviation (n = 6 per group).

^*A significant difference from control (p < .01).

^†A significant difference between HU and HU/REL (p < .01).