Adaptations to exercise are specific to the demands that are placed on the body. This is the basis of the SAID principle (Specific Adaptation to Imposed Demands). Therefore, the effectiveness of a training programme to achieve a specific goal relies heavily on the acute programme variables that are applied; these include: i) choice of exercise, ii) order of exercise, iii) load or intensity, iv) volume of exercise and v) rest periods (Fry, 2004). Within these acute variables, exercise intensity is generally acknowledged as the most important stimulus in designing optimum training programmes. The significance of intensity during exercise is of importance due to the specific relationship that exists between the training stimulus and the adaptive response (Campos et al, 2002). Thus, we need to be aware of the intensity we are working at in order to elicit the specific adaptation we require, whether that be increasing aerobic capacity, power/strength or potentially fat loss.
This article will discuss the benefits of identifying individual intensity zones in order to maximise training effectiveness for endurance cycling performance.
Lactate Threshold
The power output at lactate threshold (LT) is likely the most important physiological determinant of endurance cycling performance (Coggan, 2006). Lactate accumulates in the blood in response to an increase in speed or intensity that the athlete is working at. When exercising at intensities below the lactate threshold, there exists a balance between lactate production and removal, thereforeperformance can continue without the onset of fatigue. As intensity or speed increases there is a distinct sudden and sustained increase in blood lactate accumulation which occurs at approximately 2.5-4.0 mM of blood lactate accumulation which is referred to as the LT.
At intensities above the LT, lactate production far outweighs the ability of the muscle to remove it, therefore no steady state is achievable. Therefore, this threshold demarcates the highest intensity of exercise that can be sustained for long periods of time, making it of high importance to endurance athletes. The assessment of the LT is useful to analyse changes in fitness and has been extensively used as a predictor of endurance performance as well as for training intensity control (Beneke et al, 2011).
Lactate Does Not Cause Fatigue
Importantly, it is key to acknowledge that lactate is NOTthe cause of fatigue and in-fact may prolong exercise duration. Lactate can move out of the working muscle cell and be transported via the blood to the liver where it is converted to glucose in-order to be used as an energy substrate to fuel further exercise. Fatigue is more likely caused by hydrogen ions (H+) which dissociate from lactate. These H+ accumulate in the working muscle which result in a drop in pH level of the muscle, creating an acidic environment. This in turn effects the sensitivity of the cell membrane to nerve stimulation, therefore reducing the ability of the muscle to forcefully contract. Accumulation of other metabolites such as inorganic phosphate, and potassium may also play a role in the onset of fatigue.
Threshold Testing
The most precise way of determining an athletes lactate threshold would require laboratory equipment and invasive blood sampling. However, determination via this approach is difficult for ordinary athletes. As a consequence, more practical field based tests can be used as surrogates of the LT. One of the most commonly used tests is the functional threshold power test (FTP) which is defined as the
highest power output that can be sustained in a steady state (Coggan, 2006). This method has proved popular with coaches and athletes as it allows the intensity of exercise to be accurately prescribed, it can be used to measure training adaptations and can also be used to determine the training load (Coggan, 2006). Practically, FTP corresponds to the highest average power that can be sustained for approximately 60 minutes. Due to the physical and psychological challenges of performing a 60 minute maximal test, the FTP can be calculated by subtracting 5% from the average peak power achieved over a 20 minute time trial (Coggan, 2006).
Relative FTP Values
Larger riders may be able to express larger absolute power values due to increased muscle mass. In order to compare like for like, it is more pertinent to use relative power values which represent a power to weight ratio.
Therefore, once an FTP value has been established dividing this value by body weight will result in a relative FTP value. Ideally, we would like this value to be as high as possible, which would indicate a higher power output was possible for a given kg of body weight. Increasing power output can be achieved at training within high training zones (discussed later) and also by following a heavy resistance training program.
Heavy strength training using exercises such as squat and leg press have been shown to improve average power output during 40 minute all out time trial for cyclists (Ronnestad, 2009).
Fig. 1. Relative FTP values across different categories of cyclists.
Training Zones
Below are suggested training zones prescribed using an individuals FTP. There is an inverse relationship between power output and duration in which power can be sustained. Therefore, shorter training sessions will fall towards the higher zones whereas longer durations will be lower zones. These zones are the basis for a structured traning plan (table below) and ensure that daily training sessions are precisely targeted towards a specific, clear goal. Using specific training goals will not only make the best of your training time but also maximise the adaptation from the training session.
(Coggan, 2006)
References
1. Campos, G., Luecke, T., Wendeln, H., Toma, K., Hagerman, F., Murray, T., . . . Staron, R. (2002). Muscular adaptations in response to three different resistance-training regimens: Specificity of repetition maximum training zones. European Journal of Applied Physiology, 88(1-2), 50-60. doi:10.1007/s00421-002-0681-6
2. Fry, A. C. (2004). The Role of Resistance Exercise Intensity on Muscle Fibre Adaptations. Sports Medicine, 34(10), 663-679. doi:10.2165/00007256-200434100-00004
3. Beneke R, Leithäuser RM, Ochentel O. Blood lactate diagnostics in exercise testing and training. Int J Sports Physiol Perform. 2011;6(1):8–24. PubMed ID: 21487146 doi:10.1123/ijspp.6.1.8
4. Coggan, A. (2006). Training and racing with a power meter. Boulder, CO: VeloPress.
5. Rønnestad, B. R. (2018). Strength Training for Endurance Cyclists. Concurrent Aerobic and Strength Training,333-340. doi:10.1007/978-3-319-75547-2_22