Learning effects in over-ground running gait retraining: A six-month follow-up of a quasi-randomized controlled trial.

This study evaluated learning and recall effects following a feedback-based retraining program. A 6-month follow-up of a quasi-randomized controlled trial was performed with and without recall. Twenty runners were assigned to experimental or control groups and completed a 3-week running program. A body-worn system collected axial tibial acceleration and provided real-time feedback on peak tibial acceleration for six running sessions in an athletic training facility. The experimental group received music-based biofeedback in a faded feedback scheme. The controls received tempo-synchronized music as a placebo for blinding purposes. The peak tibial acceleration and vertical loading rate of the ground reaction force were determined in a lab at baseline and six months following the intervention to assess retention and recall. The impacts of the experimental group substantially decreased at follow-up following a simple verbal recall (i.e., run as at the end of the program): peak tibial acceleration:-32%, p = 0.018; vertical loading rate:-34%, p = 0.006. No statistically significant changes were found regarding the retention of the impact variables. The impact magnitudes did not change over time in the control group. The biofeedback-based intervention did not induce clear learning at follow-up, however, a substantial impact reduction was recallable through simple cueing in the absence of biofeedback.

Peak Muscle and Joint Contact Forces of Running with Increased Duty Factors.

PURPOSE: Running with increased duty factors (DF) has been shown to effectively reduce external forces during running. In this study, we investigated whether running with increased DF (INCR) also reduces internal musculoskeletal loading measures, defined as peak muscle forces, muscle force impulses, and peak joint contact forces compared with a runners' preferred running pattern (PREF). METHOD: Ten subjects were instructed to run with increased DF at 2.1 m·s -1 . Ground reaction forces and three-dimensional kinematics were simultaneously measured. A musculoskeletal model was used to estimate muscle forces based on a dynamic optimization approach, which in turn were used to calculate muscle force impulses and (resultant and three-dimensional) joint contact forces of the ankle, knee, and hip joint during stance. RESULTS: Runners successfully increased their DF from 40.6% to 49.2% on average. This reduced peak muscle forces of muscles that contribute to support during running, i.e., the ankle plantar flexors (-19%), knee extensors (-18%), and hip extensors (-15%). As a consequence, peak joint contact forces of the ankle, knee, and hip joint reduced in the INCR condition. However, several hip flexors generated higher peak muscle forces near the end of stance. CONCLUSIONS: Running with increased DF lowers internal loading measures related to support during stance. Although some swing-related muscles generated higher forces near the end of stance, running with increased DF can be considered as a preventive strategy to reduce the occurrence of running-related injuries, especially in running populations that are prone to overuse injuries.

Traditional high jump Gusimbuka Urukiramende: Could early 20th century African athletes beat Olympic champions?

During the first half of the 20th century, extraordinary high jumping performances of East-African athletes were observed. These athletes used a specific native jumping style called Gusimbuka Urukiramende. Eye-witnesses believed that these performances could have been world-records and that these athletes could have competed at the Olympics. However, these athletes never participated in international competitions and there is no other proof to support these performance claims. We have analysed historical photos and cine sequences of these jumps, documented the movement analysis of this technique, quantified performance and compared it to contemporaneous elite performances. Our analyses demonstrate that Gusimbuka Urukiramende athletes did not jump as high as the world record. Nevertheless, even though they used a suboptimal jump technique (because they had to lift their bodies higher to cross the bar) they could cross bar heights of 188 cm or 106% body height and as such their performance still was worthy of participation to the Olympics.

Do Performers' Experience and Sex Affect Their Performance?

This cross-sectional study aimed at developing a biomechanical method to objectify voluntary and unpredictable movements, using an automated three-dimensional motion capture system and surface electromyography. Fourteen experienced theater performers were tested while executing the old man exercise, wherein they have to walk like an old man, building up a sustained high intensive muscular activity and tremor. Less experienced performed showed a different kinematics of movement, a slower speed of progression and more variable EMG signals at higher intensity. Female performers also differed from males in movement kinematics and muscular activity. The number of the trial only influenced the speed of progression. The performers showed results which could be well placed within the stages of learning and the degrees of freedom problem.

Initial foot contact and related kinematics affect impact loading rate in running.

This study assessed kinematic differences between different foot strike patterns and their relationship with peak vertical instantaneous loading rate (VILR) of the ground reaction force (GRF). Fifty-two runners ran at 3.2 m · s-1 while we recorded GRF and lower limb kinematics and determined foot strike pattern: Typical or Atypical rearfoot strike (RFS), midfoot strike (MFS) of forefoot strike (FFS). Typical RFS had longer contact times and a lower leg stiffness than Atypical RFS and MFS. Typical RFS showed a dorsiflexed ankle (7.2 ± 3.5°) and positive foot angle (20.4 ± 4.8°) at initial contact while MFS showed a plantar flexed ankle (-10.4 ± 6.3°) and more horizontal foot (1.6 ± 3.1°). Atypical RFS showed a plantar flexed ankle (-3.1 ± 4.4°) and a small foot angle (7.0 ± 5.1°) at initial contact and had the highest VILR. For the RFS (Typical and Atypical RFS), foot angle at initial contact showed the highest correlation with VILR (r = -0.68). The observed higher VILR in Atypical RFS could be related to both ankle and foot kinematics and global running style that indicate a limited use of known kinematic impact absorbing "strategies" such as initial ankle dorsiflexion in MFS or initial ankle plantar flexion in Typical RFS.

Biomechanics of spontaneous overground walk-to-run transition.

The purpose of the present study was to describe the biomechanics of spontaneous walk-to-run transitions (WRTs) in humans. After minimal instructions, 17 physically active subjects performed WRTs on an instrumented runway, enabling measurement of speed, acceleration, spatiotemporal variables, ground reaction forces and 3D kinematics. The present study describes (1) the mechanical energy fluctuations of the body centre-of-mass (BCOM) as a reflection of the whole-body dynamics and (2) the joint kinematics and kinetics. Consistent with previous research, the spatiotemporal variables showed a sudden switch from walking to running in one transition step. During this step there was a sudden increase in forward speed, the so-called speed jump (0.42 m s(-1)). At total body level, this was reflected in a sudden increase in energy of the BCOM (0.83±0.14 J kg(-1)) and an abrupt change from an out-of-phase to an in-phase organization of the kinetic and potential energy fluctuations. During the transition step a larger net propulsive impulse compared with the preceding and following steps was observed due to a decrease in the braking impulse. This suggests that the altered landing configuration (prepared during the last 40% of the preceding swing) places the body in an optimal configuration to minimize this braking impulse. We hypothesize this configuration also evokes a reflex allowing a more powerful push off, which generates enough power to complete the transition and launch the first flight phase. This powerful push-off was also reflected in the vertical ground reaction force, which suddenly changed to a running pattern.

Mechanics of overground accelerated running vs. running on an accelerated treadmill.

Unsteady state gait involving net accelerations has been studied overground and on a treadmill. Yet it has never been tested if and to what extent both set-ups are mechanically equal. This study documents the differences in ground reaction forces for accelerated running on an instrumented runway and running on an accelerating treadmill by building a theoretical framework which is experimentally put to the test. It is demonstrated that, in contrast to overground, no mean fore-after force impulse should be generated to follow an accelerating treadmill due to the absence of linear whole body acceleration. Accordingly, the adaptations in the braking phase (less braking) and propulsive phase (more propulsion) to accelerate overground are not present to follow an accelerating treadmill. It can be concluded that running on an accelerating treadmill is mechanically different from accelerated running overground.