Thursday, 1 January 2009

getting tecky, getting tested

There has been some interest amongst my triathlon colleagues in what is referred to as the Maffetone method. Phil Maffetone promotes his philosophy primarily for long term injury prevention on the journey toward weight loss, recouperation or for older and less conditioned people wanting to improve their general health through an exercise (and diet) regime but it has been proven useful for endurance athletes and was famously employed by Ironman legend Marc Allen during certain phases of his training. His method requiers that you set a heart rate cap of (180-age) +/- a few beats for various other factors, and religiously train below that heart rate at all times. Well, very few of the people that I train with have the patience to stick with this and it has raised interesting discussions, and an experiment to compare the MAF test results of those following the method and those of us who are not.

The MAF test (nothing specifically to do with Dr MAFfetone: MAF = Maximum Aerobic Function)is conducted over 5 uniform miles, run at the (180-age) heart rate, recording the mile splits and repeated each month. Much debate was generated by the apparently arbitrary formulas (180- age); with certain individuals exceeding their threshold by merely walking fast, whilst others found themselves unable to maintain that heart rate for the duration of the test. Many had difficulty getting their head around ‘the formula’; why (180 – age)? What is significant about this threashold, and how could it be the same for everyone of that age??

Well, it seems to me that if you accept that (220- age) is a reasonable estimate of your max heart rate, and that your Aerobic and anaerobic threasholds are around 65% and 85% of your max respectively, then (max – 40) beats will stick you somewhere in the upper portion of the aerobic training zone – that which you can train at without lactic accumulation, burning predominantly fat and improve your ‘aerobic base’.

However, very few of us do accept the (220-age) formula and the evidence of the various difficulties that people were experiencing in their MAF tests demonstrates that this is righty so – especially in well conditioned older or less conditioned younger athletes. Personally, I felt that although fine as a guide for aerobic base training, (180-32)+5= 153 was about 5 beats too low for my maximum aerobic heart rate test. Based on perceived exertion and observing how my breathing changes at heart rate of 158, I modified my test heart rate to 156BPM. At this level, after a decent warm-up, I run feeling ‘comfortably uncomfortable’ at a 7:30 min mile pace. Relax a little or let my mind wander and I slow to a jog without even realizing it, apply too much focus and I’ll transit into heavier and rhythmic breathing (and run the risk of scortching the track surface in the process :o))

Testing it:

Luckily I was recently introduced to Alan Lowne of Informed Fitness, a personal trainer and fitness consultant based locally (Crouch End) who specializes in Cardiopulmonary Exercise Testing. This is more commonly referred to as Vo2 max testing – but vo2 max is just one of the things, and actually the least interesting or useful, that can be determined by this method. As the name implies the test relates cardiac and pulmonary data during exercise, and by analysis of the proportions of oxygen and carbon dioxide released in the breathe enables him to create an individual aerobic profile for the athlete. The science of this is no doubt extremely complex, but basically, aerobic exercise utilizes fat and oxygen for fuel – the exhaled by-product being oxygen. As intensity of exercise increases, CHO comes into play as a fuel source, which releases carbon dioxide. By monitoring the exhaled gases in the breathe and heart rate, Alan’s equipment is able to tell him the ‘fuel’ mix that his subject’s body is using at different exercise intensities. This can be useful for people on a weight loss plan as well as athletes wishing to gain better insight into their own individual response to exercise to maximize the benefits of their workouts and realize appropriate race intensity.

For athletes the most significant feature of the test is determining the Anaerobic Threshold. This is the point at which the body is no longer using oxygen for fuel but is entirely depending on carbs (glycogen) to fuel the muscles, and is identified by the point at which only Co2 is exhaled at an equal rate to the amount of oxygen inhaled. This point widely is accepted as being identical to the Lactate Threshold (although driven by a different system, it occurs at the same exercise intensity which causes Lactic accumulation in the blood at a rate faster than it can be cleared) and the two terms AT and LT are often interchanged to describe this point. Once this threshold has been crossed, duration of exercise at this intensity is limited – the lactic accumulation will result in increasing discomfort and muscular fatigue. It’s generally stated that we can perform for around an hour at our AT/FT. Fine for a shorter distance race, even an Olympic distance triathlon, but for anything longer it’s worth sticking well below this level if you want to maintain pace throughout the race. The good news is that by specific training it is possible to improve your Aerobic profile, thus pushing that threshold further up your heart rate range, resulting in greater output before lactic accumulation starts to ruin your fun.

The Procedure:
Alan had instructed me to arrive for my test after at least 4 hours (ideally a night) of fasting and a day (ideally 2 days) of complete rest. The reason for the fasting is to avoid any existing blood sugar responses influencing the body’s use of fuel during the test and for being well rested to enable the subject to fully exert themselves and be in their best possible condition for current fitness during the test. The test was conducted on a stationary bike - though it is possible to test on a treadmill also this tends to be less common, I assume that this is for practical reasons of maintaining a good pickup form the heart rate transmitter (typically that part of the body remains more still whilst riding than running) and that it gives the tester more control over work output.

Having fitted me up with my mask – a cool looking set up resembling an anti- pollution mask with a hose protruding from the end - wired it up to the gas analysis box, and established a signal from my heart rate transmitter, Alan first wanted to record my ‘at rest’ data to determine my basic metabolic rate. All I had to do was relax. Whether it was nerves, the strange sounds of the machinery as I breathed, the lack of sleep and emergence of a cold that I noticed the night before, but as I sat quietly trying to relax, whilst breathing through my mouth, I could feel my heart racing. After 10 minutes, during some of which Alan had left the room to help me relax, we had collected enough ‘steady’ data (about 4 minutes worth) to make an assessment of my resting heart rate and basic metabolic rate. I suspect that although I had followed Alan’s directions as regards the fasting and a rest day prior to the test, I can think of a few other factors as mentioned above that might have had an effect on this. Certainly I have recorded a resting heart rate lower than 70 BPM (it is usually around 50-55) which is what the readings showed us – still these were ‘real life’ conditions and although possibly not ideal, will ignore for the sake of the test. This is why it is probably worth repeating such assessments periodically, as well as monitoring your own resting heart rate – not only to track improvements in aerobic profile but to provide a better chance of reliable data and identify (and react to) any unusual readings.

So, at my resting heart rate of 70 BPM I was metabolising at a rate of 1.3kcal/minute – roughly equivalent to 1900 kcal/day. For those whose objective is to loose weight, this information enables Alan to formulate a diet based on calorie counting foods, off-setting against activity and a deficit for a steady rate of weight reduction. My feeling is that this simplifies the equation much too far, and it certainly was not my prime concern, but this figure did rather surprise me and went some way to explain how a 50kg female can eat most 90kg ‘sedentary’ blokes under the table and retain relatively stable weight! I also learned that at rest around 50% of these calories are derived from carbohydrates, 50% from fats. With the amount of low intensity endurance training that I do, I had assumed that the ratios would be far more biased toward fat oxidization – a 70-30 (fat –CHO) balance is, according to Alan, ‘normal’.

Next we move onto the real test – the bit where I get on the bike and start doing some work. Alan explained that it is not necessary to perform the test to maximum in order to build a useful aerobic profile, since the relevant threshold (AT) usually occurs somewhere around 80% of max HR - however since I was also curious to establish my Vo2 max, we agreed that we would do so.

Having set the spin-bike to fit, ensured that the mask was fitted well and that all the machines and monitors were picking up and reading my heart-rate and breathing data, I start off spinning at very low resistance at a comfortable cadence, that I knew I would be able to maintain for the duration of the test. Once my heart rate begins to rise, then Alan increases the resistance on the bike whilst I maintain my cadence. We proceed like this – with gradual increase in resistance equivalent to roughly 20watts – the machine whirring, rasping and beeping at 60 second intervals as it created its data points; volume oxygen exhaled/min, volume co2 exhaled/min and hear- rate for interval. We were not making note of the power output, although this would have been an option had the equipment calibrated to do so.

I’d been pedalling for a little while and after a couple of incremental increases in the resistance began to feel a bit warm, and my heart rate had reached 140bpm. I still felt comfortable pedalling, but it seems that I had suddenly become conscious of the task. Alan apparently identified this slight shift in my focus and breathing rate and asked me to rate the effort on a 1-10 scale. I figured this was worth about a 5. At around 150bpm, whilst still relatively comfortable with the effort, I really didn’t feel like talking much as I realized that there was not the spare breathe and I needed to focus pretty hard to maintain the cadence. I rated this 6. At 160bpm I found myself shifting and searching for a more comfortable position of the handlebars of the stationary bike. It didn’t really feel like much fun. 7.5. I’d been taking the odd peek at Alan’s computer and the data points as they tracked their way diagonally across the screen. We were looking for convergence of the blue line (Co2 exhaled) with the red line (o2 intake) – as the rate of Co2 exhaled makes a rapid increase indicating that all of the inhaled oxygen is being utilized by the working muscles and expelled as Co2. Beyond this point the muscular demand for oxygen is greater than that which can be drawn in the breathe and the carb only anaerobic system kicks in - the Anaerobic Threshold. By the time my heart rate had hit 170bpm I was pretty keen to see some convergence happening. We’d agreed to take the test to ‘the max’ and my understanding is that AT is typically found at around 80% of max. I didn’t feel that there was another 20% left in reserve here and we appeared to still be some way off that threshold. So taking what little I understood of the science, I tried to convince myself that I was still well within my ‘comfort zone’, that I could maintain this intensity durig a race and that it was just the weird environment that made it feel so much harder. I knew for sure that I’ve held heart rate of 185 for the duration of a 10k running race, for example. And so we cranked it up another notch. By now I am seriously perceiving a 9.5 on the scale, and Alan joins me in willing those damn lines to converge – and keep me pedalling. At last, at 183bpm we hit that point …and Alan encourages me to just keep it there for the 60 seconds he needs of data. It’s all I can do – the test is over.

The Outcome:
HR @ AT 183bpm
Vo2max 67ml/kg/min
HR max 185bpm
Once more I was surprised by these results. Not so much that I had expected to be able to get my heart rate up to around 200bpm as has been measured previously, because I am well aware of the factors which can influence this, but more so that my AT was so high. Not that think I have an unusually high AT, it’s just at far higher intensity than I’d expected. Which makes me feel that I really am doing all of my training at very easy levels, but i dont think that this is a 'fair' interpretation of the data - just highlights my miscoceptions.

Of course Alan did explain that AT is just used as an indicator of the total Aerobic range, which is sub divided into 3 zones for training purposes. These zones are constructed as +/- 15 bpm around the 'Aerobic Base' level; at which point you are burning 50%fat/50% carbs. By specific training, involving short intervals within the different zones, the aerobic markers can be shifted thus improving the aerobic profile. The desired result being able to work the body harder whilst still utilizing the aerobic fuel system – more fuel efficient and prolonging lactic free performance. Interestigly, in respect to my MAF level, my AB HR ws 153bpm - on a bike. It is generaly accepted that equivalent heartrate for rning is 5 beats higher...thus my MAF test heartrate choice happens to be at the top of my Aerobic Zone 1.

As I now approach the end of my base preparation phase, armed with these figures I’m ready to begin the next phase of my pre Ironman New Zealand block and add some measured intensity into the routine. Alan has agreed to re test shortly after the race to assess the impact that 3 months of this type of training has had on my aerobic profile, and we will be able to view this in comparison to my race performance.

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