# Biomechanical Analysis of Running in Shoes with Different Heel-to-Toe Drops
## 4 Discussion
Thus, this may reduce a runner's risk of patellofemoral pain [15; 23]. Running shoes without a drop may be a better choice, as they can not only reduce knee joint loading but also provide better protection for the foot compared with barefoot and minimalist shoes. Future studies should further determine the long-term influence of switching to running shoes without a drop on the biomechanics of the lower extremities. The results of the current study do not support our fourth hypothesis that the peak ankle plantarflexion moment would be lower when running in shoes with large drops compared with running in shoes without a drop. However, lower peak ankle version angles and moments were found when running in shoes with 15-mm and 10-mm drops compared with running in shoes without a drop. Another study showed a significantly lower ankle plantarflexion moment during the braking phase between 12% and 40% of the standing phase for female runners when running in shoes with large drops [7]. Runners suffering from or predicted to develop Achilles tendon disease or medial tibial stress syndrome displayed prolonged ankle evasion durations and greater ankle version moments compared with the pain-free controls [33; 34]. The increase in calf triceps muscle strain may be the reason for most anecdotal reports of calf and Achilles tendon pain during the first forefoot running or running in forefoot running shoes. In other words, running in shoes with large drops may minimize the net ankle moment during running and decrease the loading of the Achilles tendon and the calf triceps for runners prone to Achilles tendon disease and medial tibial stress syndrome. Our results also provide evidence for the clinical observations that running in shoes with a 10-mm drop was associated with a higher rate of knee joint injuries and a lower rate of ankle and foot injuries compared with running in shoes without a drop. The previous study showed that the rate of knee joint injuries was 26% when running in shoes with a 10-mm drop, which was greater than that (15%) when running in shoes without a drop, whereas the rate of ankle and foot injuries was 31% when running in shoes with a 10-mm drop, which was lower than that (41%) when running in shoes without a drop [19]. This was mainly due to the magnitudes of knee and ankle joint loading. The results of our study revealed that the peak knee extension moment was 3.11 \(\pm\) 0.51 N-m-kg\({}^{-1}\) when running in shoes with a 10-mm drop, which was 15% greater than the 2.70 \(\pm\) 0.69 N-m-kg\({}^{-1}\) recorded when running in shoes without a drop. The results of the current study also revealed that the peak ankle version moment was 0.48 \(\pm\) 0.14 N\(\cdot\)m-kg\({}^{-1}\) when running in shoes with a 10-mm drop, which was 25% lower than the 0.64 \(\pm\) 0.32 N\(\cdot\)m-kg\({}^{-1}\) recorded when running in shoes without a drop. These results, combined with the results of the previous studies, indicate that wearing shoes with a 10-mm drop may be disadvantageous for runners with knee weakness and advantageous for runners with ankle weakness [7; 19]. These findings can help runners, physicians, and running shoe designers better understand the potential mechanism of running-related injuries and contribute to the development of running shoes.