Table 5.

Effects of chronic overload on slow-twitch neuromuscular junctions in young adult and aged plantaris muscles.

Pre-synaptic nerve terminal branching
Variable	Young Control	Young Overload	Aged Control	Aged Overload	P value
Branch number	6.3 ± 0.6	6.7 ± 1.0	6.5 ± 1.1	7.0 ± 0.9	0.95
Total length of branching (µm)	240.3 ± 33.1	242.3 ± 31.7	220.2 ± 35.3	296.8 ± 58.4	0.60
Average length/branch (µm)	38.9 ± 2.5	36.6 ± 1.9	34.0 ± 5.6	41.7 ± 5.1	0.82
Branching complexity	15.2 ± 3.5	16.2 ± 3.8	14.3 ± 4.2	21.1 ± 5.8	0.70
Post-synaptic endplate structure
Variable	Young Control	Young Overload	Aged Control	Aged Overload	P value
Total perimeter (µm)	144.3 ± 62.5	120.7 ± 40.9	105.3 ± 56.7	190.8 ± 52.4	0.16
Stained perimeter (µm)	283.0 ± 34.9	269.2 ± 26.7	269.0 ± 13.7	306.7 ± 16.9	0.65
Total area (µm²)	725.3 ± 130.6	648.4 ± 76.5	738.9 ± 74.9	801.1 ± 79.9	0.42
Stained area (µm²)	480.1 ± 56.9	470.9 ± 47.0	454.7 ± 34.2	581.7 ± 67.3	0.57
Dispersion (%)	67.8 ± 4.5	76.5 ± 4.7	62.0 ± 5.1	72.4 ± 5.4	0.51
Pre- to post-synaptic coupling	2.3 ± 0.9	2.2 ± 0.7	2.6 ± 0.8	2.7 ± 1.0	0.92

Values are means ± SE.

Branching complexity = branch number × total branch leangth/100.

Dispersion = stained area/total area

Pre- to post-synaptic coupling = endplate’s stained area/total nerve terminal branch length.