Ventilation And Durability
by George Blackwell
For this week’s newsletter I want to outline some bits on the concept of ‘threshold durability’, why it might be important for ultra-endurance athletes, and what some recently published research is indicating on how we can measure it.
The concept of durability overall is quite simple. You do your baseline test in a moderately fresh or ‘tapered’ state, whether that’s in the lab, an FTP test, or maybe a MAF heart rate run or bike test to see your power output or pace for a given heart rate. Now, if you were to do this test immediately after a 2.5-hour easy aerobic session or after a hard week of training, would your results be the same? The answer is almost unequivocally, no. Despite this, many athletes will continue to train according to their ‘fresh’ threshold values, which can severely skew the desired intensity distribution of training across a week and potentially lead to overtraining.
While the concept overall is simple, measuring it in real time can be more challenging. The concept of ‘heart rate drift’ is well understood and has been used as a reference point for the deterioration of thresholds, where you’ll see heart rate increasing for a given intensity over time. However, it’s been noted that this drift in heart rate is disproportional to the change in thresholds, whether power output or pace, along with being very individual to the given athlete. So, heart rate drift is very difficult to interpret for athletes in longer sessions of 3, 4, or 5 hours. Instead, what we are looking for is a metric that holds constant in a relative sense to aerobic (LT1) and anaerobic (LT2) thresholds over time. In other words, as your LT1 deteriorates, another metric that we can see in real-time and which also changes a proportional amount.
The recently published research by Stevenson et al. has highlighted the potential use of ventilation as a means of monitoring intensity in real time. They hypothesised that you might expect to see overall ventilation increasing at a given power output as time goes on. However, they found that the overall volume of air breathed per minute was fairly stable when fresh and after 150 minutes of exercise, but the way this air was ventilated was different. After the 2.5 hours of effort, air was coming from a higher frequency of shorter sharper breathes.
This indicates that overall ventilation is stable from fresh, lab-based tests through to after 150 minutes of training, so it could have potential as a ‘within-session’ means of intensity regulation for athletes. If overall ventilation for a given power is rising, you may need to back off the power as your thresholds may not be as durable as you thought. The tricky bit again, is that overall ventilation is tough to measure outside the lab without a metabolic cart however it shows there is potential for it to be used if the technology becomes available!
References:
Stevenson, J.D., Kilding, A.E., Plews, D.J. and Maunder, E., 2023. Prolonged exercise shifts ventilatory parameters at the moderate-to-heavy intensity transition. European Journal of Applied Physiology, pp.1-7.
Maunder, E., Seiler, S., Mildenhall, M.J., Kilding, A.E. and Plews, D.J., 2021. The importance of ‘durability’in the physiological profiling of endurance athletes. Sports medicine, 51, pp.1619-1628.