Using Tri-Axial Accelerometry in Daily Elite Swim Training Practice

Abstract

Background: Coaches in elite swimming carefully design the training programs of their swimmers and are keen on achieving strict adherence to those programs by their athletes. At present, coaches usually monitor the compliance of their swimmers to the training program with a stopwatch. However, this measurement clearly limits the monitoring possibilities and is subject to human error. Therefore, the present study was designed to examine the reliability and practical usefulness of tri-axial accelerometers for monitoring lap time, stroke count and stroke rate in swimming. Methods: In the first part of the study, a 1200 m warm-up swimming routine was measured in 13 elite swimmers using tri-axial accelerometers and synchronized video recordings. Reliability was determined using the typical error of measurement (TEM) as well as a Bland-Altman analysis. In the second part, training compliance both within and between carefully prescribed training sessions was assessed in four swimmers in order to determine the practical usefulness of the adopted accelerometric approach. In these sessions, targets were set for lap time and stroke count by the coach. Results: The results indicated high reliability for lap time (TEM = 0.26 s, bias = 0.74 [0.56 0.91] with limits of agreement (LoA) from −1.20 [−1.50 −0.90] to 2.70 [2.40 3.00]), stroke count (TEM 0.73 strokes, bias = 0.46 [0.32 0.60] with LoA from −1.70 [−1.94 −1.46] to 2.60 [2.36 2.84]) and stroke rate (TEM 0.72 str∙min−1, bias = −0.13 [−0.20 −0.06] with LoA from −2.20 [−2.32 −2.08] to 1.90 [1.78 2.02]), while the results for the monitoring of training compliance demonstrated the practical usefulness of our approach in daily swimming training. Conclusions: The daily training of elite swimmers can be accurately and reliably monitored using tri-axial accelerometers. They provide the coach with more useful information to guide and control the training process than hand-clocked times.

Differences in swimming smoothness between elite and non-elite swimmers

“…An important aspect of our study is that the jerk cost was measured with one accelerometer on the back of the swimmer in contrast to studies in other sports where the jerk cost was measured with several markers and video recordings (Choi et al, 2014;Hreljac, 2000). This method has the benefit of the practicality of use in the daily training situation for longer periods, i.e., a complete training session (Ganzevles et al, 2017). This opens up a wide range of possibilities for coaches and researchers.…”

“…All measurements were performed in a 50=m indoor swimming pool with a constant water temperature of 27°C (Sloterparkbad, Amsterdam, The Netherlands). The same sensor and sensor position as described previously was used: a Zephyr Bioharness 3, placed on the upper back midway between the inferior angle of the left and right scapula using Tegaderm semi-permeable film dressing (10 cm×12 cm) (Ganzevles et al, 2017). This sensor consists of a tri-axial accelerometer with a range of −16 g to +16 g and a 12-bit resolution, which gathered and saved data in the binary format at a sample frequency of 100 Hz.…”

“…The data from the first arm stroke until the final stroke before the finish were used for further processing. LT, SR and SC were calculated from the accelerometer data using the algorithms described in Ganzevles et al (2017) Next, the data around the z-axis were filtered using a second-order Butterworth band-pass filter between 0.1 and 1 Hz to detect zero-crossings. The zero-crossings were defined as the change from negative to positive around the z-axis and used as an operational definition of the begin and end of a stroke.…”

“…in which a is the acceleration of the swimming body measured on the back of the participant (Ganzevles et al, 2017). The JC was subsequently averaged per lap for each swimmer.…”

“…Unfortunately, this method is rather expensive and time consuming, and not applicable in daily training settings for generating real-time feedback to coaches and swimmers (Alberty, Sidney, Huot-Marchand, Hespel, & Pelayo, 2005). Instead, tri-axial accelerometry might be used in real-time to provide characteristics such as stroke rate (SR), stroke count (SC) and lap times (LT) (Davey, Anderson, & James, 2008;Ganzevles, Vullings, Beek, Daanen, & Truijens, 2017;Magalhaes, De, Vannozzi, Gatta, & Fantozzi, 2015). However, the instantaneous velocity profile is difficult to obtain due to the orientation problem of the sensors (Dadashi, Crettenand, Millet, & Aminian, 2012;Stamm & Thiel, 2015).…”