### INTRODUCTION

### MATERIALS AND METHODS

*ad libitum*. The animals were randomly and equally distributed into five groups:

Control (C): no intervention, euthanized on 42nd day.

Lesion (L): underwent nerve compression on day 21 of the experiment, euthanized 21 days postoperatively (PO).

Trained+Lesion (TL): were trained with resistance exercise for 20 days, 3 times a week. Subsequently underwent nerve compression on day 21, euthanized 21 days PO.

Lesion+Exercise (LE): underwent nerve compression on day 21 of the experiment, and later performed resistance exercise for 20 days, and euthanized 21 days PO.

Trained+Lesion+Exercise (TLE): trained with resistance exercise for 20 days, 3 times a week. On day 21 of the experiment, they were subjected to nerve compression, and subsequently submitted to resistance exercise for 20 days, euthanized 21 days PO.

### Resistive exercise protocol

### Experimental model sciatic nerve compression

### Sciatic function index

### Histomorphometric analysis

^{2}, resulting in 108 intersections by photomicrograph. The matching intersections in the endoneurium were counted in 4 fields per nerve (photomicrographs with 100×objective), totalling 432 points per animal using Image Pro-Plus 6.0. The relative tissue area was calculated by the rule of three: multiplying the number of matching points on the straight line intersections on the connective tissue (endoneurium) by 100 and dividing the result by the total number of points.

### Statistical analysis

*t*-test when there was a statistically significant difference. Significance was defined as

*P*<0.05. The results were expressed using

*F*statistics and averages.

### RESULTS

### Sciatic function index

*F*[5, 330.6]= 16.9,

*P*=0.0001) with the C group demonstrating greater SFI in comparison to the other groups (

*P*=0.0001). When comparing the evaluations, there was also a statistically significant difference between the evaluation 1 (EV1) and EV2–EV5 (

*P*=0.0001); EV1 was greater than the following groups and there was also a statistically significant difference between EV2 and EV6 (

*P*=0.004), the smallest EV2 that EV6 (Table 2).

### Nerve fibre diameter

*F*[4, 20]=6.86,

*P*=0.001) for nerve fibre diameter with decreasing diameter in the groups L (

*P*<0.001), TL (

*P*=0.005), LE (

*P*<0.001), and TLE (

*P*=0.0318), compared to C. There was also a statistical significant difference between LE and TLE groups (

*P*=0.0254), with the TLE group having a larger diameter (Fig. 1A).

### Axon diameter

*F*[4, 20]=7.08,

*P*=0.001) for axon diameter with the groups L (

*P*<0.001), TL (

*P*=0.0036), and LE (

*P*<0.001) having a smaller diameter compared to group C. There was also a statistically significant difference between the TLE and LE groups (

*P*=0.0107), with the TLE group having the highest average (Fig. 1B).

### Myelin sheath diameter

*F*[4, 20]=5.014,

*P*=0.006) for myelin sheath diameter, with the L (

*P*=0.0012), TL (

*P*=0.0185), LE (

*P*<0.01), and TLE (

*P*=0.0403) groups showing a smaller diameter than group C (Fig. 1C).

### Average density of nerve fibres

*F*[4, 20]=4.1,

*P*=0.013) for nerve fibre density with a lower average density in the TL (

*P*=0.0219) and LE (

*P*=0.0081) groups, compared to group C. There was also a statistically significant difference between the TLE group compared to TL (

*P*=0.0134) and LE (

*P*=0.0049) groups, with the TLE group having a higher average (Fig. 2B).

### Blood vessels density

*F*[4, 2]=4.0,

*P*=0.0147) for blood vessel density with TL (

*P*= 0.0215) and TLE (

*P*=0.0426) groups showing an increased density compared to C group. The L group was also statistically significantly lower than the LE (

*P*=0.0034), TL (

*P*=0.0374), and TLE (

*P*=0.0073) groups (Fig. 3A).

### Connective tissue percentage

*F*[4, 2]=9.3,

*P*=0.0004] for connective tissue with groups L (

*P*<0.001), TL (

*P*<0.001), LE (

*P*<0.001), and TLE (

*P*=0.0158) showing an increased percentage of connective tissue in comparison to group C. The TLE group was statistically significantly higher than the LE group (

*P*=0.009) (Fig. 3B).

### Cell nuclei density

*F*[4, 2]=41.1,

*P*=0.0136) for cell nuclei density, with increasing density in the groups L (

*P*=0.0044), LE (

*P*=0.0132), and TLE (

*P*=0.0226) compared to group C. The TL group also had a statistically significantly lower average compared to L (

*P*=0.0132) and LE (

*P*= 0.0379) groups (Fig. 3C).