Joint stiffness and running economy during imposed forefoot strike before and after a long run in rearfoot strike runners.

Research has focused on the effects of acute strike pattern modifications on lower extremity joint stiffness and running economy (RE). Strike pattern modifications on running biomechanics have mostly been studied while runners complete short running bouts. This study examined the effects of an imposed forefoot strike (FFS) on RE and ankle and knee joint stiffness before and after a long run in habitual rearfoot strike (RFS) runners. Joint kinetics and RE were collected before and after a long run. Sagittal joint kinetics were computed from kinematic and ground reaction force data that were collected during over-ground running trials in 13 male runners. RE was measured during treadmill running. Knee flexion range of motion, knee extensor moment and ankle joint stiffness were lower while plantarflexor moment and knee joint stiffness were greater during imposed FFS compared with RFS. The long run did not influence the difference in ankle and knee joint stiffness between strike patterns. Runners were more economical during RFS than imposed FFS and RE was not influenced by the long run. These findings suggest that using a FFS pattern towards the end of a long run may not be mechanically or metabolically beneficial for well-trained male RFS runners.

Impact of a Long Run on Injury-Related Biomechanics with Relation to Weekly Mileage in Trained Male Runners.

The purposes of this study were to compare selected biomechanical variables before and after a long run, and to assess the relationship between weekly running volume and changes in lower limb biomechanics after the run. Twelve trained habitual rearfoot strike male runners ran overground before and after a treadmill long run while kinematic and kinetic data were recorded. Repeated measures analysis of variance and Cohen's d effect sizes were used to compare kinematic and kinetic variables before and after the run. Loading rate was 6% higher after the run (p < .05) but this difference had a small effect size (d = .32). Moderate effects were found for a 25% increase in peak ankle eversion (d = 0.62) and a 10% increase in hip adduction (d = 0.60) after the run. These findings suggest that the completion of a submaximal long run does not yield potentially injurious lower limb biomechanics in uninjured rearfoot strike runners. Weekly running mileage was not correlated to biomechanical changes observed before and after the long run. Since biomechanical responses to the long run varied among runners, differences in other factors such as specific training regimens and neuromuscular control should be considered in future studies.

Lower Limb Kinematics and Metabolic Cost During Elliptical Exercises and Treadmill Running.

The purpose of this study was to compare knee and hip joint kinematics previously associated with anterior knee pain and metabolic cost among conditions including treadmill running (TR), standard elliptical (SE), and lateral elliptical (LE) in healthy runners. Joint kinematics and metabolic parameters of 16 runners were collected during all 3 modalities using motion capture and a metabolic system, respectively. Sagittal knee range of motion (ROM) was greater in LE (P < .001) and SE (P < .001) compared with TR. Frontal and transverse plane hip ROM were greater in LE compared with SE (P < .001) and TR (P < .001). Contralateral pelvic drop ROM was smaller in SE compared with TR (P = .002) and LE (P = .005). Similar oxygen consumption was found during LE and TR (P = .39), but LE (P < .001) and TR (P < .001) required greater oxygen consumption than SE. Although LE yields similar metabolic cost to TR and produces hip kinematics that may help strengthen hip abductors, greater knee flexion and abduction during LE may increase symptoms in runners with anterior knee pain. The findings suggest that research on the implications of elliptical exercise for injured runners is needed.

Comparison of ankle kinematics and ground reaction forces between prospectively injured and uninjured collegiate cross country runners.

Biomechanical comparative studies on running-related injuries have included either currently or retrospectively injured runners. The purpose of this study was to prospectively compare ankle joint and ground reaction force variables between collegiate runners who developed injuries during the cross country season and those who did not. Running gait analyses using a motion capture system and force platform were conducted on 19 collegiate runners prior to the start of their cross country season. Ten runners sustained running-related injuries and 9 remained healthy during the course of the season. Strike index, peak loading rate of the vertical ground reaction force, dorsiflexion range of motion (ROM), eversion ROM, peak eversion angle, peak eversion velocity, and eversion duration from the start of the season were compared between injury groups. Ankle eversion ROM and peak eversion velocity were greater in uninjured runners while peak eversion angle was greater in injured runners. Greater ankle eversion ROM and eversion velocity with lower peak eversion angle may be beneficial in reducing injury risk in collegiate runners. The current data may only be applicable to collegiate cross country runners with similar training and racing schedules and threshold magnitudes of ankle kinematic variables to predict injury risk are still unknown.