Table 3.

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

Pre-synaptic nerve terminal branching
Variable	Young Control	Young Overload	Aged Control	Aged Overload	P value
Branch number	5.8 ± 0.5	5.4 ± 0.4	5.8 ± 0.4	4.7 ± 0.6	0.37
Total length of branching (µm)	164.5 ± 14.4	158.9 ± 15.3	163.1 ± 14.1	142.1 ± 30.1	0.86
Average length/branch (µm)	28.8 ± 1.8	29.1 ± 2.8	28.7 ± 1.2	30.0 ± 2.4	0.91
Branching complexity	14.3 ± 2.7	12.4 ± 1.8	14.0 ± 2.0	11.1 ± 3.7	0.83
Post-synaptic endplate structure
Variable	Young Control	Young Overload	Aged Control	Aged Overload	P value
Total perimeter (µm)	168.1 ± 16.1	175.4 ± 20.7	150.9 ± 10.3	176.8 ± 27.5	0.83
Stained perimeter (µm)	198.4 ± 16.6	208.7 ± 28.9	203.6 ± 18.9	189.1 ± 23.8	0.94
Total area (µm²)	461.4 ± 54.0	523.4 ± 79.0	479.2 ± 64.2	451.8 ± 83.0	0.89
Stained area (µm²)	347.8 ± 40.2	431.2 ± 66.0	356.5 ± 55.2	387.2 ± 55.9	0.72
Dispersion (%)	76.3 ± 1.9	81.4 ± 2.5	73.1 ± 4.5	76.0 ± 8.3	0.74
Pre- to post-synaptic coupling	2.2 ± 0.2	2.6 ± 0.3	2.3 ± 0.4	2.7 ± 0.6	0.28

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.