19 June 2007
SWIMFORMATION PHYSIOLOGY MODEL AN EXACT MATCH WITH WORLD RECORD!
The stroke rating tempo used by distance phenomenon Kate Ziegler to break the 19 year old world record of legend Janet Evans show an amazing match with the physiological model of New Zealand High Performance Programmes Director Clive Rushton recently published at swimformation.
Leading USA swim site, swiminfo reports, ‘Ziegler Shatters Evans’ World Record in 1500 Freestyle’, datelined 17 June and carries a detailed analysis of the race by Kevin Milak of swimtools detailing breakout times, tempo (stroke rate), stroke cycles, 50m lap times and elapsed times.
Milak recorded stroke tempo at four points during most of the 50m laps with a few being restricted to three measurements (probably due to excitement!). When these are graphed against the race distance and shown as swimformation intensity zones they fit uncannily accurately to the projected model.
Ziegler’s pace control was outstanding. The first and final 50m laps were 29.23 seconds and 29.27 seconds whilst the other 28 laps averaged 31.57 seconds with a standard deviation of only 0.15!! (data source: Hy-Tek Meet Result report). To achieve this consistency meant precise control of the energy output throughout the race whilst swimming at the extreme edge of human capability. On the first 50m Ziegler’s stroke rate or cycles per minute (cpm) was in the mid to low 50’s, exactly what you’d expect when starting a world record swim. Then from 100m through around 400m it gradually settles down towards the 45 cpm mark. This is a significant rating because Rushton identifies it as the start of zone 5 intensity and the exact mid-point of the rating associated with ‘Critical Velocity’. To quote Rushton’s ‘The Effect of Biomechanics on Physiology’:
Zone 5 starts where the ST fibres have to change from aerobic oxidative to aerobic glycolytic processes to cope with the increasing tension demands of the exercise – all three fibre-types are now not only engaged (as they have been since zone 3) but operating towards the limit of their capabilities. Further increases in speed will be brought about by more frequent activation of the fibres but not by the availability of different energy sources, therefore, this is a critical point of the [stroke rate] range. The speed at which the swimmer performs when this critical [stroke rate] is reached is termed “critical velocity” or “V-Crit.”
The range of tempo identified by Rushton to produce this critical velocity is very tight, 44 to 46 strokes per minute for freestyle which sits on the cross-over point between lactate clearance intensity (zone 4) and the highly complex zone 5 comprising three overlapping physiological effects, lactate tolerance, VO2Max and lactate production. Ziegler finely balances the lactate clearance and lactate production for the next 600m by averaging 45.6 cpm (highest 46.8, lowest 44.2), then gradually builds the pressure over the next 250m as she moves towards the lactate tolerance area of the final stages of world record swims. The final 250m are swum at an average of 47.5 cpm but during this phase she understandably starts to dig in and the range extends up to two peaks of 51.9 cpm and 50.9 cpm. Swimming the race any other way would not have been as efficient.
Kevin Milak’s raw data can be found here and full details of ‘The Effect of Biomechanics on Physiology’ can be found at swimformation
Clive Rushton
19 June 2007