Fig. 7

Comparison of the forces exerted by the spermatozoa with linear motility from in semen sample with 100% progressive motility (n = 15) and from semen sample with a progressive motility lower than 80% (n = 16), in both cases, the spermatozoa are trapped by the tail (a). Forces of spermatozoa swimming linearly in samples with 100% progressive motility (n = 15) and spermatozoa with circular movement (n = 17), the circular motile sperm cells are trapped by the head, while the linear motile spermatozoa by the tail (b). Data are reported in box plots (+) shows the mean, while (-) indicates the median value. Significance level *p ≤ 0.05, **p ≤ 0.01, and ***p ≤ 0.001