There are multiple variables which affect overall power production and hence speed of a cyclist during an event. These include external and internal factors. However it is our inherent physiology which has the most influence on our performance and the reason why training this beyond apparent limits is key for success at cycling.
Performance cycling at all levels relies upon excellent endurance, cardio-respiratory fitness and fatigue resistance. A good aerobic capacity plus a high degree of well conditioned anaerobic muscle power have consistently been highlighted as the main physiological components related to the production of energy through metabolism and the ability of the body to use oxygen.
There are FIVE main physiological determinants (limiters) of performance which have been well established:
– VO2Peak or MAXIMUM OXYGEN CONSUMPTION (MOC)
Cardio-respiratory fitness is defined as the ability to deliver sufficient blood to the muscles and tissues involved in cycling where oxygen is consumed and used for energy production. Usually a high VO2Peak (60- 90ml/min/kg) for oxygen consumption can indicate above average conditioning. Values towards the higher end of this range are associated with competitive excellence, although not always. In fact the existence of a true ‘peak’ in oxygen consumption is under question, due to the effects of the brain suppressing damage to vital organs. Due to the variability in VO2Peak measurements between subjects and little effect training has on different occasions within the same rider, this parameter is known to be a poor predictive indicator of endurance cycling, setting relevant training zones to track training adaptations over time.
Much scientific discussion has taken place on what factors limit VO2max, but most likely, VO2max is limited by a combination of steps in the oxygen delivery and consumption process. These are cardiopulmonary restrictions (stroke volume and cardiac output), limitations in oxygen carrying capacity (haemoglobin and capillary density) and limitations in the oxygen consumption capacity of muscle mitochondria.
An improvement in any one (or combination) of the other factors described below may easily compensate for a low VO2Peak value.
– CYCLING EFFICIENCY & ECONOMY
These determinants describe how well the body is able to convert the utilisation of oxygen (oxygen cost) and food (internal energy, calories) into power (work done), as a rate or percentage. Usually calculated by measuring the proportion of calories (as indicated by respiratory exchange gas ratio VO2/VCO2), and the resulting biomechanical power output. Mechanical efficiency (gross efficiency) reflects the percentage of total chemical energy expended that contributes to external work, with the remaining energy lost as heat. On average, mechanical efficiency ranges between 17 and 29% during steady-state cycling for amateur to elite level.
Cycling economy shows its importance during prolonged exercise, where performance depends on the aerobic capacity and the ability to maintain a low as possible VO2. Improving exercise economy is mainly due to:
• endurance training.
• eliciting improved muscle oxidative capacity and associated changes in muscle fiber recruitment patterns.
• reductions in exercise ventilation and heart rate for a given exercise intensity
• an improved exercise technique.
Factors that determine cycling efficiency are:
Fibre-type distribution, genetics, pedalling cadence, training, diet, over-training, body size, gender, fitness level and skills.
Concerning fibre type distribution, it seems that the percentage type I muscle fibers is significantly correlated to cycling efficiency, indicating that a higher percentage type I fibers result in a better cycling efficiency.
Inefficiencies are usually due to poor muscle recruitment and/or non-optimal metabolic function.
– ANAEROBIC CAPACITY (aka Critical Power Profile)
Is an unfortunate term, as it confuses the fact that it is an estimation of the energy available above lactate threshold that a cyclist can use to produce power before experiencing fatigue. I.e The anaerobic capacity is represented by both aerobic Type I and anaerobic Type II muscle ability to achieve maximal mean powers for durations of effort usually less than 20 minutes. The anaerobic capacity can be determined by the critical power profile, and different riders display vastly different profiles depending on their training state and discipline, sprinting, flat, hill-climbing etc. Typically, when training to improve the anaerobic capacity, the lactate threshold suffers as a consequence. Therefore training both limiters should be a key goal in any effective training programme.
– LACTATE THRESHOLD (LT)
The most important determinat of endurance cycling, indicates how both the anaerobic and aerobic systems are working in synergy to achieve the highest endurable power output. (Ability to sustain a high percentage of VO2Peak without accumulating lactate).
Untrained individuals usually reach LT at about 60 % of VO2Peak.
Moderately trained athletes reach LT at 65-80 % VO2Peak.
Elite and professional endurance athletes reach LT at 85-95 % VO2Peak.
See the science of Lactate here.
Lactate threshold (LT) can be seen as one of the most trainable components listed above, as many sport scientists and professional coaches acknowledge the benefits of measuring LT as one of the strongest predictors of cycling performance. LT can be estimated as either the heart rate or power output achieved under time–trial effort or ‘the race pace’ sustainable for a medium duration (30 – 90 minutes) and is easily measured using an incremental step-test and finger-prick analysis tailored to each rider.
However, more crucially it dictates how much power you have to play with during a race or how fast or long you can sprint for at the end, as it determines recovery intensity and how much muscle glycogen is saved. LT is related to Critical Power although they are defined differently and provide separate insights into performance and ability, and hence should not be confused. FTP is a crude estimation of LT, a single value which does not consider the wealth of multiple lactate/ heart-rate and power data.
Factors which affect the rate of lactate accumulation:
Depleted glycogen stores will result in a faster onset of blood lactate accumulation.
• Training status
Proper training develops four primary mechanisms to slow the rate of lactate accumulation: Higher mitochondrial density allows for greater lactate metabolism. Superior fatty acid oxidation prevents lactate production at sub-maximal exercise intensities. Preferential metabolism of fat over glycogen will preserve glycogen as a fuel source for continued exercise. Greater capillary density improves both oxygen delivery to and lactate removal from the active muscles.
• Muscle composition
Slow twitch (Type I oxidative) muscle fibers produce less lactate at a given workload than fast twitch (Type II glycolytic) muscle fibers. Although there is a substantial genetic component, effective conditioning through training can influence the remodelling of fast (Type IIX/d) fibers into intermediary (Type IIA) cross functional, predominantly oxidative fast-twitch fibers.
• Distribution of workload
A large muscle mass working at a moderate intensity will produce less excess lactate than a small muscle mass working at a high intensity.
LT is therefore an excellent physiological marker to measure, for anyone wanting to assess the effectiveness of their training programmes and fitness progression towards competition, an event or even just to have a good understanding of where their fitness is every year. The test is performed under controlled lab conditions to provide an accurate determination of your LTP, LT power-to-weight (watts/kg) estimates and lactate clearance value (an indicator of recovery) for future comparisons.