The Effects of Plyometric Warm-up on Lower Limb Muscle Activity and Time to 10m in the Backstroke Swimming Start

Abstract

The backstroke swim start is an explosive, discrete skill. Swimmers often perform plyometric warm-up protocols, such as repeated jumps, prior to their race. The purpose of this study was to determine the impact of repeated drop jumps performed immediately prior to a backstroke start. Nine elite backstroke swimmers performed three starts after a standard swimming warm-up, and three after an additional plyometric warm-up (three drop jumps from a height of 0.4 m) prior to each start. Timing and peak activation of gluteus maximus and vastus lateralis activity were measured using wireless surface electromyography. Hip and knee angles, wall contact time, head entry distance and time to 10 m were recorded using digital video cameras positioned at the side of the pool. On average, starts performed after the plyometric warm-up had a 0.1±0.09 s longer time to 10 m, peak gluteus maximus activity occurred 0.09±0.13 s later and peak vastus lateralis activity occurred 0.15±0.16 s earlier. Head entry distance was inversely proportional to time to 10 m (r =-0.80) across both conditions and should be considered as a training target. Performing plyometric warm-ups immediately prior to races may have a negative impact on backstroke start time to 10 m.

Different Lower-Limb Setup Positions Do Not Consistently Change Backstroke Start Time to 10 m

“…In contrast, swimmers who have produce less power may find the extended setup position where they can take advantage of decreased drag during the flight phase is more appropriate. Building upon our previous research [3,17], the negative correlation between head entry distance and time to 10 m indicates that head entry distance continues to be a valuable, inexpensive tool for coaches to quickly estimate start performance when comparing different start techniques. * Participants 2, 7 and 9 were male.…”

“…Correlations can help identify variables that are closely related to time to 10 m and may be more easily captured by coaches. Our past studies that examined backstroke start equipment changes [3] and warm-up modifications [17] found strong correlations between head entry distance and time to 10 m. Studies completed by other researchers have also shown lower start times which are associated with increased entry distances [5,23]. Although the correlation was only fair in this study, it still supports the relationship between head entry distance and time to 10 m. Accordingly, it is clear that the relationship between head entry distance and start time holds across a wide range of situations.…”

“…The order in which participants performed the two start types was determined based on their study-specific code such that half of the participants started with the flexed setup position and half started with the extended setup position. Two minutes of rest were given between starts, which has been found to be an adequate recovery period for backstroke starts [3,4,17,18,23,25]. The pool bulkhead was instrumented with a tri-axial waterproof force plate (OR6-WP-2000, AMTI, Waterdown, MA, USA), which was faced with an ultra-high molecular weight polyethylene sheet (EZ-Glide 350, Eclipse Sports, Cambridge, ON, Canada).…”

“…It is not often implemented in swimming due to the challenges associated with waterproofing the instrumentation [13][14][15]. Nevertheless, EMG has been used to determine muscle activation patterns in backstroke starts [16], as well as to compare differences between different start conditions [17,18]. It is important to understand both timing and intensity of muscle activity; however, a recent review indicates that most studies only report intensity and that analysis of timing is a significant gap in the literature [13].…”

“…Accordingly, the purpose of this study was to compare two different backstroke start setup positions and determine if one results in better performance than the other. Our primary outcome measure was time to 10 m, which has been used to evaluate start performance in previous backstroke start studies [3,17,23]. We did not measure multiple distances since previous work has identified that time to 5 m, 10 m and 15 m all had statistically significant differences of the same polarity between two start conditions [23].…”