Table 2.

Tetanic properties of single motor units in human hand muscles

	Intrinsic(n= 7)	Extrinsic(n= 9)	Pooled(n= 16)
Maximum force(mN)	141.0 ± 18.8	71.5 ± 12.6	101.9 ± 13.7
	28.9–168.9	23.8–139.0	23.8–168.9
Frequency for maximum force(Hz)	34.7 ± 6.3	40.6 ± 4.6	38.0 ± 3.7
	14.0–66.0	18.0–66.0	14.0–66.0
Frequency for 50% tetanic force(Hz)	11.0 ± 1.8	12.8 ± 1.5	12.0 ± 1.1
	5.2–16.9	8.8–20.8	5.2–20.8
Force at 8 Hz(% maximum force)	34.0[25.6–75.5]	34.7[20.68–38.9]	34.3[23.8–41.7]
	22.1–75.8	13.9–41.7	13.9–75.8
Frequency of peak fusion(Hz)	17.3 ± 3.1	19.6 ± 1.9	18.6 ± 1.7
	8.0–33.0	12.0–30.0	8.0–33.0
Frequency for 50% fusion(Hz)	6.1 ± 0.8	8.0 ± 0.8	7.2 ± 0.6
	3.2–9.5	3.3–10.7	3.2–10.7
Twitch:tetanic ratio	0.27 ± 0.05	0.24 ± 0.03	0.25 ± 0.03
	0.11–0.45	0.14–0.45	0.11–0.45
Peak slope(mN Hz−1)*	9.1[4.4–12.9]	2.9[2.3–3.1]	3.3[2.5–8.3]
	1.0–13.0	1.2–4.4	1.0–13.0
Frequency range for peak slope(Hz)	10.0[6.0–12.0]	8.0[6.0–16.0]	9.0[6.0–12.0]
	6.0–12.0	6.0–27.0	6.0–27.0

Data are expressed as means ± S.E.M. and range; non-parametric data (in italics) are expressed as the median, interquartile range (in brackets) and range.

^*Significant difference between intrinsic and extrinsic motor units at P < 0.05.