Fig 1.
(A) Insoles for the stimulation of cutaneous receptors (from left to right: control insoles, low-density (LD) insoles, linear spacing between nodules: 2.8cm; high-density (HD) insoles, linear spacing between nodules: 1.7cm. (B) Inertial measurement units (IMUs) arrangement.
Fig 2.
Quantification of foot loading distribution during rowing.
(A) Force, contact area and CoP computed for the instant of peak force as well as over the whole drive phase. Data are referred to the right side of participant 6 (male, 18 years, 84 kg, 1.85 m) while rowing at 18 strokes/min with the control insoles. Profiles have been averaged over the 30 central rowing cycles of the trial (mean and standard deviation are respectively shown with continuous and dashed lines). Vertical dashed lines indicate the instant of peak force (black) and the catch instant (grey). (B) Pressure values detected by each of the 99 sensors of the instrumented insole (darker intensities indicate lower pressure values). Circles denote the sensors which pressure value was greater than the 15 kPa threshold, defining the absence of foot contact, whereas the crossed circle indicates the coordinate of pressure distribution along the foot fore-rear direction.
Fig 3.
Effect of cutaneous stimulation on foot loading distribution and knee and trunk flexion-extension movements.
Representative graphs referred to the left side of participant 6 (male, 18 years, 84 kg, 1.85 m, 32 strokes/min). With the HD insoles, his force and contact area values at peak force were about 21% and 9% greater than those observed for the LD insoles, and 28% and 14% greater than those observed for the control insoles. Similar effect was found for the HD insoles with respect to the whole drive phase: +22% and +14% of force and contact area with respect to LD insoles, +32% and +17% with respect to control insoles. For each insole and parameter, profiles have been averaged over the 30 central rowing cycles of each trial. Data for different insoles are presented with different traces (Control: thick grey line; LD: thin, black dashed line; HD: thin, black line). Vertical black dashed lines indicate the instant of peak force; vertical grey dashed lines indicate the catch instant.
Fig 4.
Changes in foot loading with cutaneous stimulation during rowing.
Mean and standard deviation (whiskers) values are shown for (A) the peak force, (B) contact area and (C) the fore-rear CoP position at the instant of peak force. Group data averaged over the drive phase are shown in panels (D), (E) and (F) respectively. Different insoles are represented with different grey intensities (black: Control; dark grey: LD insole; light grey: HD insole), separately for the left and right foot. Asterisks denote statistical significance for pair-wise comparisons with Bonferroni correction at P<0.05.
Table 1.
Average power and distance travelled for each of the three stroke rates considered (no main effect for insole type observed, P>0.21 for both parameters).