**3. Results**

The knee flexion angle was predetermined and monitored in real time for all measurements on the ski simulator, and the results revealed that there were no statistically significant differences in knee flexion parameters. There were also no statistically significant differences in knee rotation parameters, whether with the ski waist-width parameter or with time before or after fatigue (Figure 3).

**Figure 3.** External tibial rotation in a prefatigued state (before F) and at different times after fatigue (after F) with two different ski waist-widths.

The knee abduction was significantly larger in connection with the wide skis (Figure 4) compared to the narrow ones (*t* = −5.1; *p* < 0.01; *d* = 0.46).

**Figure 4.** Knee abduction/adduction in a prefatigued state (before F) and at different times after fatigue (after F) with two different ski waist-widths. + depicts statistically significant difference compared to prefatigued state (*p* < 0.05); \* depicts statistically significant difference between all-narrow against all-wide waist-width measurements.

After fatigue, there was significant increase in knee abduction with narrow skis (*t* = −2.16; *p* = 0.05; *d* = 0.31), as well as with the wide ones (*t* = −2.39; *p* < 0.05; *d* = 0.41).

Significant differences were observed in VAP with wide skis compared to narrow ones (F = 3.78; *p* < 0.05; η2 = 0.27) (Figure 5).

**Figure 5.** Center of pressure (CoP) velocity in anteroposterior direction (VAP) in a prefatigued state (before F) and at different times after fatigue (after F) with two different ski waist-widths. + depicts statistically significant difference compared to prefatigued state (*p* < 0.05); \* depicts statistically significant difference between all-narrow against all-wide waist-width measurements.

The VAP value for wide skis was significantly higher compared to that for narrow ones (*t* = −3.44; *p* < 0.01; *d* = 0.52). With narrow skis, all three after fatigue VAP values were significantly higher compared to the prefatigue value with the immediate after fatigue value being the highest (*t* = −2.70; *p* < 0.05; *d* = 0.42).

There were significantly higher VML values with wide skis (F = 19.94; *p* < 0.01; η2 = 0.67) compared to narrow ones (*t* = −4.87; *p* < 0.01; *d* = 0.70) (Figure 6).

**Figure 6.** CoP velocity in mediolateral direction (VML) in a prefatigued state (before F) and at different times after fatigue (after F) with two different ski waist-widths. + depicts statistically significant difference compared to prefatigued state (*p* < 0.05); \* depicts statistically significant difference between all-narrow against all-wide waist-width measurements.

The effect of time was statistically significant for narrow skis only (F = 4.42; *p* < 0.01; η2 = 0.29). Specifically, there was an increment in VML immediately after fatigue compared to the prefatigue state with narrow skis (*t* = −3.73; *p* < 0.01; *d* = 0.56).

The results demonstrated significant differences in Aap values between different ski widths (F = 4.89; *p* < 0.05; η2 = 0.31) (Figure 7).

**Figure 7.** CoP amplitude in anteroposterior direction (AAP) in a prefatigued state (before F) and at different times after fatigue (after F) with two different ski waist-widths. \* depicts statistically significant difference between all-narrow against all-wide waist-width measurements.

The AAP values were significantly higher with wide skis compared to narrow ones (*t* = 2.23; *p* < 0.05; *d* = 0.31). The differences between pre and after fatigue times were significant with wide skis only (F = 4.28; *p* < 0.05; η2 = 0.28). There was a decrement in AAP value 2 min after fatigue compared to the state immediately after fatigue (*t* = 2.92; *p* < 0.05; *d* = 0.38).

There were significant differences in AML values between different ski widths (F = 20.36; *p* < 0.01; η2 = 0.63). The AML values were significantly higher with wide skis compared to narrow ones (*t* = −5.18; *p* < 0.01; *d* = 0.69) (Figure 8).

**Figure 8.** CoP amplitude in mediolateral direction (AML) in a prefatigued state (before F) and at different times after fatigue (after F) with two different ski waist-widths. + depicts statistically significant difference compared to prefatigued state (*p* < 0.05); \* depicts statistically significant difference between all-narrow against all-wide waist-width measurements.

The effect of time of measurement was statistically significant for narrow skis only (F = 5.00; *p* < 0.01; η2 = 0.31) and AML was significantly higher only immediately after fatigue (*t* = −3.44; *p* < 0.01; *d* = 0.52).

Significant differences were observed in MFAP with different ski widths (F = 5.93; *p* < 0.01; η2 = 0.37). The MFAP value was significantly lower with wide skis compared to the narrow ones (*t* = 2.86; *p* < 0.05; *d* = 0.43) (Figure 9).

**Figure 9.** The mean frequency of the power spectrum of CoP in the anteroposterior direction (MFAP) in a prefatigued state (before F) and at different times after fatiguing (after F) with two different ski waist-widths. + depicts statistically significant difference compared to prefatigued state (*p* < 0.05); \* depicts statistically significant difference between all-narrow against all-wide waist-width measurements.

The differences between different times of measurement were significant with wide skis only (F = 3.38; *p* < 0.05; η2 = 0.30) and MFAP was significantly higher 2 min after fatiguing compared to the prefatigue value (*t* = −4.17; *p* < 0.01; *d* = 0.66), as well as 4 min after fatigue compared to the prefatigue value (*t* = −3.32; *p* < 0.01; *d* = 0.50). With narrow skis, there was a significant increment in MFAP value only at 4 min after fatigue compared to the prefatigue value (*t* = −3.5; *p* < 0.01; *d* = 0.53).

There were significant differences in MFML values with time of measurement (F = 3.96; *p* < 0.05; η2 = 0.36), as well as with different ski widths (F = 3.70; *p* < 0.05; η2 = 0.35) (Figure 10).

MFML was significantly lower with wide skis compared to narrow ones (*t* = 2.33; *p* < 0.05; *d* = 0.31). With narrow skis, there was a significant increment in MFML values 4 min after fatigue compared to the prefatigue state (*t* = −3.85; *p* < 0.01; *d* = 0.55), as well as 4 min after fatigue compared to immediately after fatigue (*t* = −2.73; *p* < 0.05; *d* = 0.40). With wide skis, there was significant difference in MFML value only 4 min after fatigue compared to values 2 min after fatigue (*t* = −2.33; *p* < 0.05; *d* = 0.31).

With AR values, there were significant differences with different times of measurement (F = 5.36; *p* < 0.01; η2 = 0.52), as well as with different ski widths (F = 4.33; *p* < 0.05; η2 = 0.46). There were significantly higher AR values with wide skis compared to narrow ones (*t* = −3.67; *p* < 0.01; *d* = 0.53). With respect to different measurement times, there were significant differences in AR value with narrow skis only (F = 5.58; *p* < 0.01; η2 = 0.34) with all the after fatigue values being significantly higher compared to the prefatigue state.

**Figure 10.** The mean frequency of the power spectrum of CoP in the mediolateral direction (MFML) in a prefatigued state (before F) and at different times after fatigue (after F) with two different ski waist-widths. + depicts statistically significant difference compared to prefatigued state (*p* < 0.05); \* depicts statistically significant difference between all-narrow against all-wide waist-width measurements.
