During the stimulation period the patient remained in a mini-squat position at thirty degrees and returned to zero degrees during the decay period. During the electrical stimulation off period, the patient spontaneously performed another mini-squat at 30 degrees without electrical stimulation. The patients in the CKC + NMES placebo group simulated the same work applied to the NMES group. Notably, this group was also connected to the electrodes, but the equipment was set at a stimulus intensity of zero.

We used a 10-channel electrical stimulation device with a 2500-Hz carrier frequency. We used four channels in the synchronous mode, with surface electrodes that were simultaneously fixed at the motor points of the quadriceps and hamstrings.

During the stimulation period, i.e., the on time, the patient remained in a mini-squat position at thirty degrees and returned to zero degrees during the decay period. During the electrical stimulation off period, the patient spontaneously performed another mini-squat at 30 degrees without electrical stimulation. The patients in the CKC + NMES placebo group simulated the same work applied to the NMES group. Notably, this group was also connected to the electrodes, but the equipment was set at a stimulus intensity of zero.

We used a electrical stimulation device with a 2500-Hz carrier frequency. We used four channels in the synchronous mode, with surface electrodes that were simultaneously fixed at the motor points of the quadriceps and hamstrings. Initially, a warm-up protocol that was five minutes long was used at a stimulation frequency of 40 Hz to activate the slow fibers. These fibers activated with a four-second-contraction time (on), a four-second-stimulus rise time, a four-second-stimulation decay time and a 12-second relaxation time (off).

We then increased the frequency to 70 Hz to activate the fast fibers for an additional 10 minutes using the parameters described above, and finally, the frequency was increase to 150 Hz for 10 minutes to achieve maximal muscle potentiation.

We only observed a significant improvement in the flexibility of the posterior muscle chain for the CKC + NMES group during the initial evaluation compared to the partial evaluation (p=0.012), the partial evaluation compared to the final evaluation (p=0.035) and the initial evaluation compared to the final evaluation (p=0.008). Regarding the scale that was used to classify the level of flexibility, 10% of the subjects in the CKC + NMES group were initially classified as good/excellent. At the end of the protocol, 60% of the subjects were classified as good/excellent (p=0.015)

A significant improvement in muscle strength was only observed in the group treated with CKC + NMES. The improvement in quadriceps strength occurred during the first 10 sessions (p=0.001) Muscle strength in the hamstring muscle group responded similarly to the quadriceps muscle group (i.e., a significant improvement in muscle strength was only observed in the CKC + NMES group) in both the initial evaluation compared to the partial evaluation at 10 sessions (p=0.009) and the initial evaluation compared to the final evaluation (p=0.006)