## 4 Discussion  
The present study aimed to determine the effects of running kinematics during foot contact on the peak upper trunk accelerations captured by an accelerometer embedded within a commonly used GPS tracking device. Variables of running kinematics were separated into two categories: joint/segment kinematics at IFC, MS and TFC, and peak segment velocities between IFC-MS and MS-TFC. Analyzing these variables independently, through GLMMs, allowed for insights into which joint/segments have the largest effect on the peak upper trunk accelerations, during which key gait event this occurs and the effect of the subsequent peak velocities of the bodily segments during the impact (IFC-MS) and propulsion (MS-TFC) subphases of foot contact. GLMM summaries showed that category 2 fixed effect variables (peak segment velocities) had a larger effect (F value) than the category 1 fixed effect variables (joint/segment kinematics) on the RES, VT and ML accelerometer peak accelerations (Table 1). In addition, running speed had a greater residual effect on the category 2 fixed variables (Table 2). To our knowledge, these comparisons have not been previously reported; however, they  
Figure 4: Category 1 and 2 variables with a significant effect (\(p\) < 0.05) on the peak ML accelerations of the GPS-based accelerometer at each key gait phase. F value and fixed effect coefficient (\(+\) = direct, \(-\) = inverse) are displayed within the brackets of each variable. The direction of the arrows represents the motion of the joint/segment that has a significant effect at each key gait phase. substantiate the relationships described by [PERSON] (2004) on the determinants of bodily segmental accelerations when exposed to impact forces during running. These findings infer that including segment velocities in future studies can lead to a better understanding of the intersegmental relationship during running instead of focusing on joint kinematics alone, as seen in previous studies [7; 19; 33]. It has previously been well documented that increased joint stiffness and stability around the lower limb segments result in less GRF attenuation and more force transferring up the kinetic chain, leading to greater impact and propulsion forces during running [19; 34; 35]. Our results support findings from [PERSON] et al. (2014) as decreased knee flexion at IFC increases the shank segment's stability, reducing the shank's peak linear and angular velocities during the impact subphase (IFC-MS) and causing greater peak accelerometer accelerations (Figure 1). The shank segment had the largest effect on peak RES (F value = 129.2, Figure 1) and ML (F value = 49.2, Figure 4) accelerometer accelerations of all peak segment velocities, thus displaying its important role in the transfer of GRF throughout the kinetic chain. Additionally, during MS, the role of the ankle is apparent as there is a medium-sized effect of decreased ankle flexion resulting in larger RES (F value = 10.0, Figure 1) and VT (F value = 18.2, Figure 2) peak accelerations, suggesting that larger acceleration peaks are related to reduced decoupling of the ankle joint. Increased joint stiffness can increase propulsion forces capabilities during stance [35], resulting in larger peak segment velocities. This is shown in the propulsion subphase (MS-TFC) as increased peak angular (flexion) velocity of the thigh has a large to medium-sized effect on the peak accelerometer accelerations in all axes (Figures 1-4). Furthermore, large to medium-sized effects were observed for foot segment linear (posterior and medial) and angular (internal rotation) peak velocities on the AP and ML peak accelerometer accelerations (Figures 3 and 4). These findings differ from previous investigations [19] as the ankle flexion angle was associated with TFC and they did not analyze segmental velocities, possibly due to the different accelerometer mounting sites. The proximal joints and segments of the trunk were shown in our results also to influence the peak accelerometer accelerations.