Fig 1.
Experimental setup and protocol.
A: Knee extension force was assessed with a three-dimensional sensor. Straps were placed on the hip, thighs and ankle (not shown) to limit body movements. B: Experimental protocol for each injection type. Participants performed two maximal voluntary contractions (MVC) at each time condition (baseline, following injection (< 3 min), recovery). C: Supramaximal electric stimulation was delivered to the quadriceps muscle during maximal voluntary contraction (MVC) and at rest.
Fig 2.
Maximal force and voluntary activation.
Mean (SEM) maximal knee extension force and % voluntary activation of the quadriceps muscle before, immediately following painful (hypertonic) and control (isotonic) injections, and during recovery. * p < 0.05; # p < 0.05 vs. control.
Fig 3.
RMS EMG of agonist and antagonist muscles.
Mean (SEM) RMS EMG of agonist (rectus femoris, vastus medialis, vastus lateralis) and antagonist (biceps femoris) muscles of the dominant leg. Contractions were performed before, immediately following painful (hypertonic) and control (isotonic) injections, and during recovery. No significant differences were found between conditions.
Fig 4.
Mean (SEM) RMS EMG of auxiliary muscles (gluteus maximus, erector spinae) of the dominant leg during knee extensions performed before, immediately following painful (hypertonic) and control (isotonic) injections, and during recovery. No significant differences were found between conditions.
Table 1.
Correlation between changes in MVC force following injection of hypertonic saline and other parameters.