## 4 Discussion  
The body's centre of gravity (_CoG_) and centre of body mass (_CoM_) are often used interchangeably. However, authors do not always realise that these are not the same concepts. Their interchangeable use in human body analysis is acceptable because the human body has approximately uniform density, is relatively small compared to the mass of the Earth, and functions in a uniform gravitational field. It is common to apply the general _CoG_ determined in passive conditions [16; 17] to dynamic situations, which is inappropriate because the tilting segment of the body has a different centre of gravity with a different gravity value and spatial location. Therefore, it is not possible to analyse the biomechanics of the dynamic human body by analysing the dynamic human body's biomechanics as though it were a rigid body, because the vertical, supported human body tilts at the level of the axis of rotation of various joints. This is particularly evident during full support of the human body on the feet, with the axis of rotation at the level of the upper ankle joint. At that point, the centre of gravity shifts, as the mass of the feet is no longer part of the leaning body segment. This manuscript addresses a simplified scenario--body tilt with support on both feet. In any other body position during the movement of the human body, the analysis of tilt should refer to the specific joint at which the single-plane hinge motion occurs. During gait, the body alternately shifts support between the feet; thus, only the mass of one foot should be excluded from the leaning body mass. In the case of the take-off phase of gait, from the moment of lifting the heel, the foot, except for the toes, participates in deflecting the body weight, and the axis of rotation runs mainly through the first metatarsophalangeal joint. In an extreme case, when standing on the tips of the toes, as is the case with a ballerina, the entire body weight is tilted because the axis of rotation is at the level of the distal phalanx of the hallux. Studies that apply the general _CoG_ to dynamic human body research misrepresent the actual forces and torques involved [18], which translates into the design of physiotherapeutic methods, training programs for athletes and soldiers [16], and even surgical procedures. In previous studies, the average weight of the feet was determined by the direct method through cadaver foot weighing and then determining their percentage share in the total body weight. This study presents an indirect method for determining the weight of the feet based on torque balance within the lever system. In this way, it is possible to weigh \begin{table}
\begin{tabular}{c c c c c c c c} \hline  & \(F_{2}\) [kG] & \(F_{3}\) [kG] & \(h_{1}\) [m] & \(h_{CoG\_4}\) [m] & **Body Mass [kG]** & \(W_{4}\) [kG] &
\begin{tabular}{c} **Foot Mass** \\ **[\% of Body Mass]** \\ \end{tabular} \\ \hline P1 & 52.28 & 52.14 & 1.73 & 0.0832 & 94.2 & 2.91 & 3.09 \\ \hline P2 & 56.65 & 56.49 & 1.75 & 0.0991 & 102.1 & 2.81 & 2.75 \\ \hline P3 & 50.27 & 50.13 & 1.78 & 0.0879 & 89 & 2.95 & 3.32 \\ \hline P4 & 52.37 & 52.21 & 1.74 & 0.0962 & 91.9 & 2.87 & 3.12 \\ \hline P5 & 41.72 & 41.61 & 1.69 & 0.0791 & 75.2 & 2.48 & 3.31 \\ \hline P6 & 45.70 & 45.59 & 1.71 & 0.088 & 80.9 & 2.03 & 2.51 \\ \hline Mean (SD) & 49.83 (5.33) & 49.69 (5.31) & 1.73 (0.03) & 0.089 (0.007) & 88.88 (9.62) & 2.68 (0.36) & 3.02 (0.32) \\ \hline
95\% CI & [44.2, 55.4] & [44.1, 55.2] & [1.7, 1.27] & [0.081, 0.097] & [78.7, 98.9] & [2.29, 3.051 & [2.678, 3.356] \\ \hline Margin of\_error\_95 CI & 5.59 & 5.57 & 0.03 & 0.007 & 10.09 & 0.37 & 0.36 \\ \hline \end{tabular}
\end{table} 
Table 1: Foot weight calculated by the indirect method in six men.