**3. Results**

The reliability of the outcome variables is shown in Table 2. For both muscle groups RTD-SF and TMVC showed very good reliability (all ICC ≥ 0.85; all CV ≤ 5.66%); however, the reliability was somewhat lower for RTDPEAK, especially for the VF muscles (ICC = 0.54; CV = 15.21%).


**Table 2.** Reliability of the outcome variables.

kRTD-SF—slope of regression line, r2RTD-SF—linearity of regression line, TMVC—maximal torque normalized on body weight, RTDPEAK—maximal rate of torque development normalized on body weight.

Junior players had a significantly lower average number of training years (5.5 ± 1.8 years) compared to senior players (14.1 ± 3.8 years) (t(21) = −7.2, *p* < 0.013). There was no statistically significant di fference in height between groups (t(21) = −1.6, *p* = 0.11), while senior players had statistically significantly higher body mass (t(21) = −3.4, *p* = 0.003) and body mass index (BMI)(t(21) = −3.0, *p* = 0.007). Average kRTD-SF, TMVC, and RTDPEAK values of elbow extensors and volar flexors in junior and senior group are presented in Table 3. Junior and senior players had similar values of TMVC in both muscle groups, while junior players had significantly greater RTDPEAK of EE and VF (*p* = 0.003–0.005, ES = 0.35–0.36). For both groups, a strong linear relationship (r2RTD-SF = 0.93–0.95) between the peak force and the RFD across submaximal contractions was calculated for both muscle groups (sample recordings are presented in Figure 3). There was no statistically significant di fference in kRTD-SF between junior and senior players for elbow extensors or volar flexors. There was no di fference in shooting performance from long distance, whereas senior players were more successful from short distance.


**Table 3.** Descriptive statistics and differences in measured parameters between junior and senior basketball players.

kRTD-SF—slope of regression line, r2RTD-SF—linearity of regression line, TMVC—maximal torque normalized on body weight, RTDPEAK—maximal rate of torque development normalized on body weight, Short distance—shooting distance at 2.3 m from the basket, Long distance—shooting distance at 8.9 m from the basket.

Significant associations between kRTD-SF, TMVC, RTDPEAK (EE and VF) with shooting performance for junior players are presented in Figure 4. We calculated a large positive association between kRTD-SF of EE and VF and shooting performance from short distance (Figure 4a,b), while significant negative large associations were seen between kRTD-SF of both muscle groups and shooting performance from long distance (Figure 4c,d). Moreover, a significant positive large association was calculated between TMVC of EE and shooting performance from long distance (Figure 4e), while the association between TMVC of VF and shooting performance was not statistically significant (Figure 4f). No statistically significant associations were calculated in junior players between RTDPEAK of both muscle groups and shooting performance (r = 0.246–0.315, *p* = 0.48–0.49). There were no significant associations between TMVC, RTDPEAK, or kRTD-SF (EE and VF) and any shooting performance in senior basketball players (r = −0.481–0.481, *p* = 0.15–0.55) or in both groups combined (r = −0.366–0.271, *p* = 0.16–0.87).

Significant positive large associations between kRTD-SF of elbow extensors and volar flexors were calculated for senior group (r = 0.677, *p* < 0.05) and when both groups were evaluated together (r = 0.615, *p* < 0.001), while associations between kRTD-SF of elbow extensors and volar flexors in junior group were not statistically significant (r = 0.514, *p* = 0.72).

**Figure 4.** *Cont*.

**Figure 4.** Associations between kRTD-SF (**<sup>a</sup>**–**d**), TMVC (**<sup>e</sup>**,**f**) of elbow extensors (EE) or volar flexors (VF) and shooting performance from short and long distance.
