Examination of the perceived agility and balance during a reactive agility task

<div><p>In vehicle dynamics, it is commonly understood that there is an inverse relationship between stability and maneuverability. However, animal studies have found that stability and maneuverability can coincide. In this study, we examine humans running a reactive agility obstacle and consider the relationship between observational perceived agility and balance, as well as the relationship between quantified surrogates of agility and balance. Recreational athletes (n = 18) completed the agility task while wearing inertial measurement units (IMUs) on their body. The task was also video-recorded. An observational study was completed by a separate group of adults (n = 33) that were asked to view the videos and score each athlete on a Likert scale for balance and for agility. The data from the body-worn IMUs were used to estimate quantified surrogate measures for agility and balance, and to assess if the relationship between the quantified agility and balance was in the same direction as the perceived relationship from the Likert scale responses. Results indicate that athletes that were given a higher Likert agility score were also given a higher balance score (<i>r</i>_<i>s</i> = 0.75,<i>p</i> < 0.001). Quantitative surrogates of agility and balance also showed this same relationship. Additional insights on technique for this reactive agility task were informed by the quantitative surrogates. We observed the importance of stepping technique in achieving the faster completion times. The fast performing athletes spent a greater proportion of the task in double support and lower overall time in single support indicating increased periods of static stability. The fast performing athletes did not have a higher body speed, but performed the task with a more efficient technique, using foot placement to enable heading changes, and thus may have had a more efficient path. Similar to animal studies, people use technique to enable agile strategies while also enabling increased balance across the task.</p></div

Examination of the perceived agility and balance during a reactive agility task - Fig 2

<p><b>Two-dimensional histogram for the (a) count of rater agility vs. balance scores, (b) completion time vs. agility score, and (c) completion time vs. balance score</b>.</p

Examination of the perceived agility and balance during a reactive agility task - Fig 8

<p><b>Relationship between time in single support and (a) the normalized stride length variance, (b) the normalized number of foot contacts, and (c) cone acceleration.</b> One outlier trial was removed from the normalized stride length variance plot and correlation.</p

Estimated regression coefficients for the log of the cone acceleration dependent variable.

<p>Estimated regression coefficients for the log of the cone acceleration dependent variable.</p

Examination of the perceived agility and balance during a reactive agility task - Fig 3

<p>(a) Mean body speed and (b) variance in body speed with respect to time. The relationships were not significant between mean body speed or variance in body speed with completion time.</p

Estimated regression coefficients for the single support time with cone acceleration and endpoint location.

<p>Estimated regression coefficients for the single support time with cone acceleration and endpoint location.</p

Reactive agility course [23], adapted from Sekulic [24].

<p>Athletes received verbal cues at the location notated and touched 4 endpoint cones per trial. The order of endpoints called out were 4-3-4-1, 2-4-3-4, and 3-4-1-2. Note that not all cones were touched in each order so that there was not an expectation of which cone would be called.</p

Body speed estimated using the sacrum IMU vs. normalized time.

<p>The time was normalized from one cue to the next cue. The solid vertical line indicates the mean location of the cone within the normalized time period, with the dashed lines showing one standard deviation from the mean. (a) Mean body speed across all endpoints. The shaded gray region indicates ±1 standard deviation from the mean body speed, where the mean was calculated across 156 cue-cue time periods (52 trials, each with 3 cue-to-cue regions). (b) Mean body speed segmented by endpoint, standard deviations not shown for ease in disambiguating the mean lines.</p

Bars indicate the cumulative percent time of double support between cues 1/2, cues 2/3, and cues 3/4 for all 18 athletes over the repetitions of the course (total of 52 runs through the course).

<p>The time was normalized from one cue to the next cue. The vertical line indicates the mean location of the cone within the normalized time period, with the dashed lines showing one standard deviation from the mean.</p

Bicycle roll rate () and steer rate () versus time.

<p>Data from a representative trial (non-cyclist, <i>v</i> = 7.96 m/s) demonstrates that the steer rate () lags and is correlated to the bicycle roll rate () during riding.</p