# Temporal Stability and Practical Relevance of Velocity and Velocity-Loss Perception in Back Squat
## 4 Discussion
### Delta Score and Velocity Perception  
In agreement with previous studies [16; 17; 19], we found significantly greater PV accuracy for higher loads compared to lower ones, both in the test and re-test session after 4 weeks. Moreover, a very high correlation between Vr and Vp in both test and re-test sessions was found, suggesting that PV is a stable parameter over time. To the authors' knowledge this is the first study to examine the stability of PV after four weeks without feedback with an encoder or PV scale. Indeed, PV is not only stable over time but, as found by [PERSON] et al., it is also unaffected by mental and physical fatigue [17; 18]. Furthermore, the Ds reported in Figure 2 is comparable to what previously reported [16], indicating that the combined familiarization of PV and PVL does not appear to have altered the velocity perception accuracy. However, the Ds, which is the only parameter currently used to evaluate PV accuracy, is influenced by the presence of both positive and negative values (i.e., under or over estimation of the velocity); therefore, to accurately assess the magnitude of the error associated with PV we considered more appropriate to use the absolute difference between Vp and Vr. For the aforementioned reason, it is important to use both Ds and \(\mid\)Ds\(\mid\) to obtain information about the direction of the error as well as an accurate estimate of its magnitude. Since it is not influenced by the presence of both positive and negative values, \(\mid\)Ds\(\mid\) exhibited a slightly higher error than Ds. Therefore, PV accuracy, with an absolute error of approximately 0.11 m\(\cdot\)s\({}^{-1}\) when using light loads, does not appear sufficiently precise for prescribing VBT intensity, potentially leading to incorrect load selection. Further research is needed to enhance the  
Figure 5: \(\mid\)Vscore \(\mid\): Absolute differences between number of repetitions perceived and real number of repetitions (\(\mid\)Np \(-\) Nr \(\mid\)); Vscore 60–20: Error in number of repetitions performed with 60% 1 RM and 20% VL; Vscore 60–40: error in number of repetitions performed with 60% 1 RM and 40% VL. Vscore 80–20: Error in number of repetitions performed with 80% 1 RM and 20% VL; Vscore 80–40: error in number of repetitions performed with 80% 1 RM and 40% VL; Test: test session 48–72 h after the familiarization protocol; Re-Test: test session 4 weeks after the test session.  
accuracy of PV across the entire load-velocity spectrum used in VBT sessions. Lastly, the \(\mid\)Ds\(\mid\) exhibited a large standard deviation (i.e., -0.07 m\(\cdot\)s\({}^{-1}\)), indicating that some subjects achieved high accuracy while others were markedly imprecise. Future studies should explore the underlying mechanisms behind these differences. One possible explanation is that differences in proprioception among subjects may account for variations in PV ability. Proprioception informs force generation and, in tandem with exteroceptive senses such as visual, vestibular, and tactile feedback, may help detect changes in velocity [26]. Moreover, some studies have suggested that proprioception varies based on individual factors such as experience [26], age [27], and sex [28]. Therefore, considering that this study did not account for these differences, future research should investigate this possibility. This could involve proprioceptive training interventions or comparative analyses across groups with known differences in proprioceptive ability, such as athletes versus non-athletes or younger versus older individuals [29; 30; 28]. Lastly, within the field of neuroscience, the perception of an object's velocity is considered to be determined by a combination of proprioceptive and exteroceptive afferents, such as vision [26; 29; 30]. Future studies could also investigate the impact of visual input on PV accuracy.