We kicked off the start of the year at Peak Cycle Performance conducting a head-to-head analysis of the current training status for the members of the Nuun sponsored road-race team, based here in South-West London. The newly formed team were looking forward to their first training camp together in Mallorca, to bring some cohesion to their race plans as well as all-important preparation that the early Spring sun and mountains can bring to the start line.
However, they still had one small obstacle to over-come before boarding the plane, their 20 minute functional threshold power and heart rate test (FTP/HR). Devised by Andy Coggan and Ed Coyle this abbreviated assessment is a great indication of overall cycling performance and potential rankings in any General Classification, from a Sunday sportive to a 6 day stage race. This well-known parameter represents a cyclists 1 hour time-trial work-rate, after which muscle glycogen stores are expected to be depleted, if performed correctly.
FTP is termed functional because there are no direct physiological markers being measured (Heart rate is a substitute for VO2 kinetics). We decided to measure blood lactate concentrations throughout the test period as a window into the Team Nuun lactate kinetics (this is usually defined by a full lactate profile test).
Lactate is now known to be a valuable by-product of anaerobic metabolism even at rest, and is critical in the recycling of glucose between muscle and liver as a fuel when oxygen availability is insufficient. However, increased lactate levels affect blood pH and may cause acidosis through accumulation of Hydrogen ions (H+) in the cell/ mitochondria and blood which is ultimately responsible for exhausted muscles. This drop in pH is counteracted by the effect of Bicarbonate released into the blood to neutralise any acidosis, although this process is overwhelmed at extreme rates of muscle contraction. The lactate threshold determines the intensity at which this accumulation of Hydrogen ions and acidity occurs before the muscle has to rest prior to repeating the effort. The larger the difference between the resting exercise level (ie recovery) from the true lactate threshold value, the faster the recovery should be from any intensity greater than threshold (ie supra-threshold).
Conducted under stringent lab conditions, a properly conducted FTP test requires a specific warm-up over 25 minutes at set periods of high cadence and fixed percentage maximal heart rate for the sake of reproducibility and validity. The FTP assessment is known to be a close estimate of the maximal lactate steady state value (MLSS, an accurate heart rate and power determination used to set physiologically relevant zones), and hence was a great opportunity to see how approximate this could be in several well-trained cyclists and assist them with their training.
FT Heart rate is a surrogate for physiological stress, and is an indirect measure of oxygen delivery to the muscles and waste metabolite extraction, the closer a cyclists true physiological threshold reaches their maximum aerobic capacity (ie VO2max) the greater the proportion of their maximal aerobic power. However, the same threshold power should be sustainable at a lower heart rate, which indicates a positive improvement of fitness. Although sometimes this may be caused by illness, stress, fatigue or dehydration, and a similar reduction in the heart rate/ power ratio. In the latter case, RPE would be higher than when changes in the ratio are due to improved fitness. Even though heart rate monitoring has its limitations, the data is still very informative when combined with other performance data channels.
The resting lactate values reflect the skeletal muscle composition of both fast twitch and slow twitch fibers, as well as the rate of anaerobic glycolysis which is present even at rest (red blood cells account for some of this activity). Muscle firing patterns are different in every cyclist, and is what makes us good at our preferred disciplines. Lower resting lactate levels reflect a relatively dominant aerobic capacity, while higher levels indicate anaerobic predominance. Glycogen depletion and insulin levels may still affect lactate concentrations, but again conducting a reproducible test lets us measure the effectiveness of a training programme quite well.
The Nuun team members came into Peak Cycle Performance, above Pearson, Sheen one after each other. All looked in good shape, anticipating their ‘serious training camp cum jolly-in-the-sun’. Not knowing who was capable of what, I was sure they were out to make their mark on the team physiological assessment rankings.
First thing was to record baseline values while briefing them about the assessment, weight, percentage body fat measured through electrical impedance, blood pressure and a resting lactate value at which point a few members had put their race face on. Following a short calibration check and the formal warm-up they entered into the blinded 20 minute test period, with only intermittent feedback of heart rate and time, as to reduce bias.
Throughout the test period, members were asked to score their relative perceived exertion (RPE) during each of four phases. Blood lactate measurements were taken at the first and last phase, and then at a recorded post-test time.
There was a lot of relief at the end of the 20 minutes, as some members realised that the assessment doubles–up very well as training! After a controlled warm-down period the final recovery blood lactate was taken at 10 minutes.
Analysis of lactate kinetics is currently the most beneficial way of assessing cycling performance. In particular it has been shown that lactate threshold values as established through a graded sub-maximal protocol are superior to maximal oxygen uptake (VO2 max, which is a much more uncomfortable and less informative assessment) when assessing endurance performance in similar trained groups of cyclists. In fact, it is known that MLSS can be estimated from well defined Lactate Threshold values from a graded test without any further inconvenient assessment. This is our main performance assessment offering at Peak Cycle Performance. Lactate Threshold Concepts, How valid are they? Review, Faude, et al. Sports Med. 2009;39(6):469-90
Each member paced themselves very well for the duration of the test period, holding their constant preferred cadence. The relative perceived exertion (as a subjective appraisal of cardio-respiratory effort as opposed to leg muscle strain) acts as an internal control, to allow repeat comparisons.
As expected, absolute FTP and power-to-weight were different for each individual, although team members were quick to compare their cycling prowess against each other…which is not a valid approach except when trying to understand a cyclists unique profile…sprinter, time-trial, hill climber, track pursuit etc. The main benefits of a properly conducted assessment are to provide a head-to-head with yourself after a period of training, and using your data as a tool to steer your training, improve weaknesses and take advantage of strengths. Understanding ones unique physiology allows literally any motivated athlete to undertake specific training to create adaptations which would result in more desirable performance at an optimal rate.
After applying the principles of lactate kinetics to the FTP assessment in the Nuun team, it was very interesting to see the variation in concentrations for each team member, especially comparing the 1st and final phase of the test period. A greater than 1mmol/L change in Blood Lactate suggests that the MLSS is breached (ie. not an exact estimate). The 1st and final phase lactate concentration in a valid assessment should be close to the true MLSS value. From the table we can see how lactate, not forgetting this acts as a fuel, is tolerated by each rider. Only one member is able to hold an effort which doesn’t result in an elevated blood lactate concentration between the first and final phase measurements.
The final column shows the recovery lactate value after 10 minutes. The quicker the final phase value is able to return to its resting level, the faster the cyclist is able to recover from an intense effort. Lactate is cleared from the muscle, re-distributed and used in other muscles aerobically or reconverted by the liver. The better the lactate system is at doing this, ie creating a tolerance, the more frequently higher intensities can be reached before complete muscle exhaustion occurs. We can see an interesting variation between the member’s clearance values which aren’t necessarily related to their mid-test values.
For instance, Nuun team member A has a low resting lactate value, is able to tolerate a moderate/high amount of lactate throughout his FTP, but is unable to recover very quickly from this strong threshold effort. This may be due to a poor re-conversion of lactate back to glucose in the liver. Reconstituting glucose in this way is most important for delivery of available fuel to muscles which may be depleted of glycogen so further intense efforts can be performed more readily. Even so, this individual would be regarded as a good time-trialist yet would benefit from performing higher intensity efforts to condition their lactate system and improve their anaerobic capacity even more without compromising their high aerobic ability.
Team member B has consistent values, except for this low lactate value at the end of the first phase, suggesting they may have been more cautious to find the intensity with which to pace the duration of the test. A cautious approach is viewed better than starting too strongly, although it is probable that their FTP is an underestimation of their true value.
Nuun team member C is very interesting as his resting lactate level is in the upper typical range, indicative of someone predominantly anaerobic. This is confirmed by a very high lactate level suggesting they may have started too strong during the first phase, which drops slightly by the end of the test period. High sub-maximal lactate levels are usually seen in someone with a very good ability to sprint. Their lactate clearance is high, suggesting good recovery even after tolerating such levels of lactate for a prolonged period. However, it is obvious their threshold power is much lower than that of member A. This is a typical profile of a sprinter who relies on short bursts of speed and although they may have good aerobic capacity, may not be very efficient.
Finally member D highlights an individual who has not been training recently and is unable to sustain a high proportion of his maximal aerobic capacity, reflected in his low RPE and heart-rate values, they still have a good lactate clearance value and need to do more training just to reach their baseline fitness level by training to elevate this value at the relevant intensities for the optimal durations.
In all, the Nuun Team boys are looking in top condition for so early in the year. We can only imagine the Mallorca training camp will help their numbers go in the right direction. The data from the FTP assessment alone doesn’t translate fully into predictive race performance, which is multi-factorial and dependent on many variables. Besides the threshold value which can predict general ability in certain disciplines, critical power and anaerobic work capacity which look at short-term peak powers necessary for extremely intensive defining moments of a race will be of equal value. However, a baseline point which confirms training status can be used to measure the effectiveness of a prescribed training programme, if an improvement in lactate threshold is required or as not to compromise this when training peak power outputs. Even though it is thought that neuromuscular and anaerobic power is inversely related to maximal aerobic power, this is not always the case and either do not necessarily need to be compromised. Although when both are present, albeit a rare occurrence it is usually the sign of a great cyclist.
Wishing you effective Spring training!
(Passionate cycling specific scientist and director of CPS IN-MOTION)