Detection of Illegal Race Walking: A Tool to Assist Coaching and Judging

Abstract

Current judging of race walking in international competitions relies on subjective human observation to detect illegal gait, which naturally has inherent problems. Incorrect judging decisions may devastate an athlete and possibly discredit the international governing body. The aim of this study was to determine whether an inertial sensor could improve accuracy, monitor every step the athlete makes in training and/or competition. Seven nationally competitive race walkers performed a series of legal, illegal and self-selected pace races. During testing, athletes wore a single inertial sensor (100 Hz) placed at S1 of the vertebra and were simultaneously filmed using a high-speed camera (125 Hz). Of the 80 steps analyzed the high-speed camera identified 57 as illegal, the inertial sensor misidentified four of these measures (all four missed illegal steps had 0.008 s of loss of ground contact) which is considerably less than the best possible human observation of 0.06 s. Inertial sensor comparison to the camera found the typical error of estimate was 0.02 s (95% confidence limits 0.01-0.02), with a bias of 0.02 (±0.01). An inertial sensor can thus objectively improve the accuracy in detecting illegal steps (loss of OPEN ACCESSSensors 2013, 13 16066 ground contact) and, along with the ability to monitor every step of the athlete, could be a valuable tool to assist judges during race walk events.

IART: Inertial Assistant Referee and Trainer for Race Walking

“…The use of wearable inertial systems, even if they do not offer a direct assessment of gait temporal events, can potentially reduce the discomfort of the insole pressure systems, resulting more user-friendly in real training and competition scenarios. The first usage of inertial sensors in race walking dates back to the work proposed by Lee et al in [9]. They used a single inertial sensor (with sample frequency of 100 Hz) placed on S1 vertebra, to correlate acceleration patterns with gait temporal events, for assessment of LOGC.…”

“…First, we present the development of the infringements parameters, which we consider as the major contributions of the current work. The LOGC timing (LOGC T ) parameter is derived from acceleration data, by proposing a modification to a previous approach [9]. Starting from the LOGC T , three different LOGC classification methods have been derived, respecting the race walking competition rules.…”

“…We have used a fourth-order Butterworth low-pass filter with a cut-off frequency of 20 Hz for acceleration on x-axis (i.e., the vertical acceleration of CoM) and 30 Hz for acceleration on z-axis (i.e., an approximated value of the anteroposterior acceleration of CoM). This filter with a cut-off frequency of 20 Hz is the same used by previous related works (race walking tests using inertial sensors) [9,10]. For the z-axis, we have indeed selected a cut-off frequency of 30 Hz, to consider more details of the original signal.…”

“…The LOGC T is defined as the time that elapses between the last instant of foot contact during the stance phase, called toe-off event (TOE), and the instant in which the following foot first makes contact with the ground, called heel-strike event (HSE). For the assessment of LOGC T , we start from the definition in [9], where the LOGC T is defined as the time interval after which we can consider that the "flight is deemed to have occurred". Therefore, it is not strictly defined as "the duration of loss ground contact".…”

“…Therefore, it is not strictly defined as "the duration of loss ground contact". According to [9,14], for the i-th step, the LOGC T expression is equal to…”