Technology is evolving at a great pace. Heart Rate (HR) monitors are getting more features and are linking in with other training tools that can pick up GPS signals, foot pods that count the number of foot strikes and a whole range of other items. With this ever expanding range of training tools, comes the software to analyse the training conducted and plan future training.
What should we look at with our periodisation plans? Hours per week? Time in HR zones? Volume or intensity? What if you had a metric that could measure both?
Let me introduce to you a metric that quantifies the stressfulness of a training session known as Training Stress Score (TSS) (McGregor & Fitzgerald, 2010). The higher the TSS, the greater the training stimulus received. The more of these sessions conducted back to back the greater the chance of over-training. Although this article is about running, the concept still applies for any exercise although the technology may not yet be ready to measure it in real time on your wrist!
Each run will see a variety of intensities used for different durations. Some runs may be longer at lower intensity whilst others may be shorter at higher intensity or even intermittent in nature at higher intensities inter-spaced with lower intensity work between (intervals).
To use TSS everything is measured relative to the individual’s Functional Threshold Pace: that is the pace that the athlete can maintain for 60min. This keeps the TSS accurate based on the athlete’s current ability. It will also take into account that a hilly 40min run at an 5:00 per kilometre pace will be more stressful than a flat 40min run at the same pace; as well as any given pace is physiological stressful the longer the pace is sustained.
The calculation for TSS is relatively simple:
TSS = t x IF x IF x 100
t = Time (in hours)
IF = Intensity Factor
The trickiest part of the calculation is determining the run’s IF. This is the normalised graded pace for the run divided by the Functional Threshold Pace. To do this you need software that normalises the pace ran at. What this means is that the software converts the real pace (including hills/undulations) into a flat pace (by taking into account what the pace would have been if there were no hills/undulations). It will then grade the normalised average by dividing the run into 30sec segments. Each 30sec segment is then weighted based on the pace for that segment (taking into account the fact that the physiological stress of running increases exponentially as speed increases). Trying to work out the IF and then consequently the TSS is a nightmare on your Casio calculator. To do this you will need specific software.
The capability is there to compare the work of an athlete compared to their ‘Functional Threshold’ level in a number of sports and activities. The ability to determine the length of time spent at any intensity within a workout to indicate how much training stimulus an athlete has received, is changing how periodisation occurs in a range of sports.
Although this article is more focused towards utilising the metrics in relation to running, it can also be conducted with both swimming and cycling. With cycling utilising your Power data the TSS is more reliable than with running or swimming where you are only utilising the pace ran at.
If you would like further advice feel free to contact Coach Ray.
Coach Ray is the Head Coach & Director of Qwik Kiwi – Endurance Sports Consultant.
Coach Ray specialises in assisting first timers and recreational athletes to achieve their sporting goals. He can be contacted at www.qwik.kiwi, firstname.lastname@example.org and 021 348 729. Make sure you sign up to his monthly informative newsletter.
McGregor, S., & Fitzgerald, M. (2010). The Runner’s Edge – High-Tech Training for Peak Performance. Champaign: Human Kinetics.