Table 2.

Summary of Data for Single Motor Units Recorded From Extensor Digitorum Longus Muscle of Adult and Oldest Old Rats

	Adult Rats, n = 18 (of 19)	Oldest Old Rats, n = 10 (of 12)
Motor units measured	164	82
Motor units measured per rat	9.1±4.4	8.2±2.8
Motor unit F o (mN)	62.9±32.2	68.5±41.9
Motor unit TPT (ms)	13.9±3.6	15.8±4.2*
Motor unit HRT (ms)	14.1±4.9	17.8±7.0*
Estimated motor units per muscle	62.7±19.1	20.2±7.2*

Notes: Data are expressed as mean ± standard deviation. Note that only muscles that had six or more motor units measured were included in the analysis. F _o = motor unit maximum tetanic isometric force, TPT = time to peak tension, HRT = half relaxation time.

*Denotes statistically significant difference compared with adult rats (p < .05).