Influence of Grade and Surface Type on Tibial Impact Acceleration in Trained Distance Runners

Chronic overuse injuries are extremely common in trained distance runners. Runners develop these injuries as a result of repeated impacts to the lower extremity during running. Most trained distance runners will take millions... [ view full abstract ]

Chronic overuse injuries are extremely common in trained distance runners. Runners develop these injuries as a result of repeated impacts to the lower extremity during running. Most trained distance runners will take millions of steps each year during running. During each of these steps they take, the runners will experience these high impact forces. It is important for these runners to know if certain surface types and slopes play a significant role in the development of these large forces on their lower extremities. Therefore, these runners along with coaches and athletic trainers may be able gain useful knowledge for developing training programs that may be able to limit the impact forces experience over the millions of steps. Purpose: This study was conducted to compare tibial impact acceleration in trained distance runners on three surface types (grass, asphalt, and concrete), and three slopes (incline, decline, and flat). Methods: 13 (8 males, 5 females; mean age of 20.07 ± 0.95, height of 173.30cm ± 8.94, and weight 62.18kg ± 7.88) trained distance runners participated in this study. Participants completed a 1-mile maximal effort time trial to determine their pace for the running trials. The participants were then fitted with a skin mounted tibial accelerometer to perform 18 total running trials on multiple surface and slope conditions. Each participant ran two trials for each surface on all three of the slopes. All trials were performed at the determined pace from the timed mile for each participant. Results: Peak tibial impact acceleration was significantly different between decline running and incline running (decline= 8.04 ± 0.12 g; incline= 7.31 ±0.35 g) p= 0.02). There was no main effect for surface type. There was a significant difference between grass and concrete on the flat slope (grass= 8.22 ± 1.22g; concrete= 7.47 ± 1.65g) p=0.017). Grass resulted in a significantly greater peak tibial impact acceleration than asphalt on the incline slope (grass= 7.68 ± 1.44g; asphalt= 6.99 ± 1.69g) p= 0.03). Additionally, there were significant differences between decline and incline and between flat and incline on the asphalt surface. (decline= 8.13 ± 1.67g; incline= 6.99 ± 1.69g) p= 0.001), (flat= 7.79 ± 1.44g; incline= 6.99 ± 1.69g) p= 0.03). Conclusion: Based on the results of the current study, it cannot be sufficiently determined that certain surface types play a significant role in reducing the amount of impact forces experienced during running.  The current study can however say that slope does play a role in significantly reducing impact forces during running in regards to incline compared to decline slopes. The results of the current study may be beneficial to coaches and athletic trainers in working to reduce prevalence of lower extremity overuse injuries.