News Letter January 2013
Training with Heart Rate Zones...... some useful stuff to know.
A Heart Rate Monitor HRM measures your heart rate for given level of metabolic activity. Its important to know that your metabolic activity is affected by more than just physical demands, but also levels of fitness, fatigue, stress, emotional arousal, light, nutrition, medication, hydration.... the list goes on.
Having said this, all other things being equal, there is a very strong correlation between physical effort and heart rate, such that, the harder you swim, run or cycle, the higher your HR goes. Because the relationship is based on metabolic activity, there will always be a different response and maximal demand for different physical activities such as swim, cycle or run. This is becasue each activity employs a different mix and set of muscles; nordic skiing is particularly demanding as it employs a huge number of [prime-mover] muscles compared to, say, swimming [front-crawl] which is mostly about upper body. In simple terms, less operational muscle-mass means less oxygen demand and hence less demand on the cardio-vascular system. The differences between swim, cycle and run are approximately 5% each but this does depend on levels of demand, conditioning, muscle mass and differences in body-distribution of fibre-type.
There are three energy systems at play within the human body. All three are operating all the time, it's just the mix that varies according to the demands placed on the body. This is important to understand as one of the biggest myths within Training Systems is that the body switches cleanly from one system to another. In reality the transitions are very grey and can be influenced by specific training.
The heart also has an upper limit to beat, HR(max), which tends to decrease with age but can be sustained through training. The guide HR(max) = (220 - age years) is only really useful as a novice [to exercise] and can be inaccurate by as much as 10-15% for anyone with a couple of years consistent training under the belt.
There is often confusion about maximum HR for different disciplines, swim, cycle, run. This is a myth as the limit is actually set by the heart, as above. The apparent upper limit is due to demand imposed by the different activities and [most significantly] the level of adaptation to that sport, for example, a fully conditioned professional swimmer can easily push their heart to its limit.
We know there are links between heart rate, metabolic activity and physical effort, now we need to take this one step futher and tie-in the tricky business of response & adaptation to training. "Training" is simply a term that we use to label physical activity that is controlled and targetted to deliver a specific adaptation, such as strength, endurance, speed, etc. Adaptation comes about after repeated training sessions that reinforce a specific response, some come about relatively swiftly whilst others take much longer, maybe months, to become noticeable.
There are many physiological adaptations to training but those most relevant to performance can be grouped in response to a continuum of intensity that brings them on. Because the adaptations blend into each other and are very subjective, its useful to create bands of [HR] intensity within which the optimal response is found. These bands are also known as HR Training Zones.
Creating the right number of zones is a balance between userbility and encompassing a broad enough range of physiological adaptations that are most relevant to performance training. Subjectivity and the shere number of factors [that can influence HR] dictate that the zones cannot be too narrow, yet the need for specificity [of adaptation] means that zones can't be too broad. Having seven zones seems to be the best compromise.
The zones also need to have a point of reference that is relatively stable and reflective of current performance. The best marker for this is what's known as Functional Threshold FT, which is the "tipping point" at which aerobic energy production is surpassed by anaerobic systems. FT goes by many different names (blood lactate threshold, anaerobic threshold, max lactate steady-state MLSS, onset blood lactate OBLA) but essentially it reflects the sustainable metabolic limit for aerobic energy production and will be somewhere close to but short of VO2max. Some training systems use HR(max) as the point of referrence, however this may prove too inaccurate for anyone looking for specific adaptation.
Zone                                    % Functional Threshold HR
Zone 1    Active Recovery                      <68%
Zone 2    Endurance                            69-83%
Zone 3    Tempo                                  84-94%
Zone 4    Lactate Thrshold                    95-105%
Zone 5    VO2max                             >106%
Zone 6    Anaerobic Capacity                n/a
Zone 7    Neuro-muscular Power            n/a
Because each zone has a different "feel" (relaxed at Z2 to "lung-busting" at Z5) its easy to be misguided by personal preferrence and fall into a "comfort trap". Each zone will provide a very specific set of adaptations and its important to mix and match according to the demands of the sport being trained for.
Zone 2 is often a struggle because it does not actually feel like training and athletes often get bored and hence omit it from their training activities. If you are tempted to do this, try to understand that the purpose of training goes beyond just physiological adaptation. For example, Zone 2 is of low enough intensity that the level of impact / stress on physical structures [ligaments, tendons and muscle attachments] is also low and this is what makes it so useful during Base-phase when there is a high risk of [over-use] injury when pushing distance & duration.
Other areas of focus whilst training in Z2:
  • developing mental focus,
  • optimising movement patterns,
  • developing posture and long duration dynamic stability,
  • developing self-awareness,
  • developing the right nutrition and feeding habits (very important for all sports not just endurance activities),
  • broadening your range of experience such that you are able to respond to any surprises with a well rehearsed solution.
How to find your Functional Threshold.
The simplest and most accurate way is to have a Blood Lactate Test BLT which involves analysing blood samples (finger prick) every few minutes whilst on a run-treadmill or stationary bike. This is often combined with VO2max (gas analysis of expired air) and HR(max) testing all at the same time. The result provides a clear set of markers against which HR training zones can be calculated. There is a question as to whether this level of accuracy is actually worthwhile, given that training zones are quite broad (at least 10%).
Because VO2max, LT and (to some degree) HR(max) are both variable (influenced by the very training zones that they were used to calculate) there is a need for regular re-testing to ensure that the zones are still optimal. If re-testing is not undertaken, this would almost certainly negate the benefit of the accuracy that BLT carries over other means of determining Threshold. On this basis, the cost of re-testing every 6-8 weeks may prove prohibitive to many athletes.
A more pragmatic way to determine Threshold is to measure HR(max) with a Ramp Test and then calculate LT as 85%HR(max). Unless you are already very conditioned, its probably better to run rather than cycle, as it may be safer plus more likely that you will hit your highest cardio-vascular demands (for reasons above). There is some debate as to whether its possible to truly hit HR(max) in this way but with a good HRM and the right encouragement (!) you will get close enough.
If the Ramp-test is performed correctly, analysis of the resulting HR trace will reveal a step-change that typically occurs at around 85% of the subsequent HR(max), hence the guideline calculation above. All other things being equal, this would coincide with Lactate Threshold, if both parameters were [concurrently] monitored against load. Any discrepancy between the two simply highlights the sensitivity of HR to other factors beyond load / effort, for example, testing yourself whilst dehydrated or fatigued will certainly produce a large discrepancy.
Training with HR Zones - from a coaching perspective.
There's almost a required "leap of faith" for an athlete starting to use Training Zones and its often easy to lose objectivity through personal preferrence or lack of understanding about specificity.
As a Coach you will need to understand the current ability of your athlete and the performance demands for the sport, only then can you create a training programme that focuses of the shortfalls.
Taking shortcuts or using guesswork will only lead to an incorrect mix of training zones which would then put a "hole" in your athletes performance , for example, training in Zone 2 will not elicite many (if at all) improvements in the performance aspects associated with, say, Zone 4.
As a general rule of thumb, priority should initially be given to the lower zones as this will help to mitigate risk of injury due to repetition or tearing muscles when doing higher intensity/speed work. Put another way (in terms of periodisation) Base Phase would be mostly Z2 and focus on developing distance & duration and Build Phase in Z4/5 for developing speed.
Keep things simply, let the zones do their work and do not confuse the body with elaborate mixes during a single workout.
Adaptation only comes about after repeated reinforcement of the same training stimulus, of course this assumes adequate recovery to allow adaptation to take affect.
Re-test every 6-8 weeks to identify any changes in performance that align with the adaptations expected for the training zone you've been using.
**** This means there is no point re-testing for LT until you've been training in Z4 for 6-8 weeks ****


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Happy and safe training!


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