Table 1.

Synchrony and discharge properties for pairs of motor units residing in various muscles

Muscle	Number of Subjects	Number of Pairs	Percentage of Significant Peaks	k′	CIS	Peak Duration, ms	Firing Rate, Hz	Coefficient of Variation of the Interspike Interval
Third dorsal interosseous	11	34	70.6	2.14 ± 1.09	0.64 ± 0.53	12.4 ± 6.8	9.5 ± 1.8	0.17 ± 0.03
Extensor pollicis brevis	12	32	75.0	1.67 ± 0.38	0.47 ± 0.25	9.7 ± 3.5	10.1 ± 1.4	0.16 ± 0.03
Extensor digitorum	6	29	75.9	1.59 ± 0.31	0.67 ± 0.33	11.0 ± 3.3	11.3 ± 2.2	0.19 ± 0.03
Flexor digitorum superficialis	12	67	70.1	1.55 ± 0.34	0.40 ± 0.21	8.0 ± 2.5	10.5 ± 1.4	0.15 ± 0.03
Extensor carpi ulnaris	8	30	40.0	1.34 ± 0.24	0.30 ± 0.22	10.4 ± 3.0	10.1 ± 1.7	0.15 ± 0.02
Brachioradialis	9	30	30.0	1.23 ± 0.29	0.24 ± 0.29	10.1 ± 2.0	10.2 ± 1.3	0.13 ± 0.02
Brachialis	8	30	6.7	1.12 ± 0.11	0.15 ± 0.14	9.1 ± 2.7	11.0 ± 1.5	0.12 ± 0.02
Biceps brachii	6	30	16.7	1.17 ± 0.15	0.17 ± 0.16	8.6 ± 2.0	10.4 ± 1.3	0.13 ± 0.02
Deltoid	6	32	62.5	1.44 ± 0.23	0.43 ± 0.27	10.9 ± 2.6	10.0 ± 1.3	0.15 ± 0.02
Multifidus	5	35	17.1	1.23 ± 0.27	0.08 ± 0.09	8.0 ± 4.4	7.2 ± 1.3	0.14 ± 0.02
Vastus lateralis	4	31	12.9	1.14 ± 0.21	0.05 ± 0.07	5.1 ± 1.6	7.3 ± 1.8	0.13 ± 0.02
Semitendinosus	5	34	35.3	1.34 ± 0.38	0.15 ± 0.20	8.1 ± 3.4	7.5 ± 1.1	0.13 ± 0.03
Lateral gastrocnemius	8	35	22.9	1.32 ± 0.32	0.13 ± 0.16	10.1 ± 6.8	7.1 ± 1.3	0.14 ± 0.02
Tibialis anterior	5	31	58.1	1.60 ± 0.43	0.40 ± 0.32	14.2 ± 5.4	7.8 ± 0.9	0.14 ± 0.02
Extensor hallucis brevis	12	32	93.8	2.43 ± 0.85	0.51 ± 0.32	12.3 ± 4.2	7.2 ± 0.8	0.17 ± 0.03
Abductor hallucis	10	39	84.6	2.69 ± 1.17	0.42 ± 0.23	12.3 ± 3.3	6.6 ± 1.0	0.17 ± 0.02

The number of subjects refers to the number of subjects that contributed data from a particular muscle; 20 of 33 subjects contributed data for >1 muscle. For the percentage of significant peaks, the duration of the cross-correlogram peak was measured only for those histograms exhibiting a significant peak.