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swim training For more information on the TEI and how it can be applied to sports, you can read our article here.




Critical Speed and Training Effects

It would be expected that CS would improve with training, as would performance capacity. But it is not quite as simple as that. Provided the training program design has incorporated suitable workloads appropriate to each athlete’s initial status, then it is normally expected that performance will improve. But the degree of change and its rate of change will be very heavily dependent upon the athlete’s initial ‘fitness’ level and performance capacity: the higher the status, the slower and lower will be the performance outcomes in percentage terms. The same applies to changes in Critical Speed, but there is a complication, and it comes down to the model of Critical Speed that one is applying. At TPE Sports Coaching, we use the linear model, i.e. the value of Critical Speed is represented as the slope of a line, and so we would be looking at changes in the ‘appearance’ of that slope: is it sloping at a greater or lesser angle? If it is sloping at a greater angle, the implication is that Critical Speed has improved; while the reverse is the case if the line’s slope is reduced. But does that mean that performance capacity has been reduced? It depends. Consider the diagram below (see page 100 in our e-Book). There are several possible outcomes from a training program on the post-training value of Critical Speed.

changes in CS with training Diagram A represents a typical chart for a Critical Speed calculation: a line drawn between two data points and the slope of that line is Critical Speed.

Moving to Diagram B, which presents another line (dashed) obtained after a re-test following an hypothetical block of training. The red arrow indicates a reduction in the time taken to complete a time trial of a given distance, the longer distance of the two, while there has been no change in the time taken to complete the shorter distance. This would ordinarily translate to an improved performance capacity, and in this case, an improved Critical Speed is also seen by an upward change in the slope of the Critical Speed regression line.

Diagram C presents the opposite effect of training: no change in the longer distance, but an improvement in the time of the shorter time trial. It can be seen the slope is now slightly decreased compared with the initial slope, or to put it another way, Critical Speed has decreased. What has improved in Diagram C is the intersection of the slope with the y-axis. This point of intersection (or intercept) is generally considered to be an ‘anaerobic’ measure, and often termed ‘anaerobic work capacity’ or AWC.

Diagram D presents yet another scenario where both time trials have yielded an improved time. In this hypothetical example, the slope has remained the same, but the intercept has increased.

The take-home message here is that care needs to be taken in the interpretation of re-test results. A drop in Critical Speed, and/or an unchanged Critical Speed do not necessarily mean a decline in performance capacity.

Learn much, much more about Critical Speed and how to incorporate it into your training program in our eBook, Critical Speed and the Physiology of Training: The PEATS program.