Should you follow your heart or your head?

The two most significant things I have learnt this year have been to challenge what I have been told, ask questions, read, draw from experiences and then make my own conclusions. Not everything we read is true and not everything we are taught is correct – we are often ill informed through nothing more than ignorance. Research advances changing theories and challenging our beliefs.

The second thing is that the human mind is the most powerful tool we have, and yet we seldom flex it and strengthen it as we do our other muscles. It has the ability to affect our physical performance to such a degree that we can excel or fail in spite of our physical readiness.


I began to realise that when I was asking a lot of my body I needed to prepare mentally as well. The brain is a very clever organ that will try and protect you and conserve energy when ever it can. It will try and trick you into feeling tired, telling you that you cant continue and that you need to stop. This perception of effort will slow you down and make you stop if you let it. Related to this feeling of exhaustion is the theory that we can only push our bodies so far before we reach a lactate threshold.


But what is this lactate threshold? Historically we have been told that muscles rely on oxygen to produce energy via an aerobic pathway, but when the energy demands increase, as the work of the heart increases and get too high the body has to turn to anaerobic energy production. It is said to occur at a heart rate level of around 60% in untrained individuals and up to 80% in elite athletes.

The theory goes that the by product of this anaerobic pathway is a waste product called lactic acid.




A misconception is that lactic acid is the result of muscle fatigue and that it pools in the muscles and eventually reaches a level whereby we can no longer effectively use them. Firstly lactic acid does not exist in the body, lactate however is a fuel which is used by the muscles to actually delay the onset of fatigue ( See Weiland Gevers work for more detail).


More recently research has shown that lactate helps prevent depolarisation of muscle fibres and is not a major factor in muscle fatigue ( Dutka and Lamb, Effect of lactate on depolarization-induced Ca2+release in mechanically skinned skeletal muscle fibres, American Journal of Physiology, 2000). So essentially without the production of lactate the muscles would fatigue much sooner.


In 2006 George Brooks studied mitochondria and discovered that most of the lactate produced in a cell never leaves it and that lactate is continuously formed throughout aerobic exercise. He showed that oxidative and glycolitic pathways (aerobic and anaerobic) of energy production are in fact linked rather than separate ( read more : Brooks, ).


One of the main flaws with the lactate threshold is that there is actually no set limit to which the muscles cease working. You do not hit lactate threshold and fall over. Lactate has been shown to rise exponentially in line with exercise intensity due to increased production, not increased use. So a higher level is needed to fuel the harder working muscles. If there was an actual threshold – even one that increased with training, you would still a reach a point (e.g. in sprints or hard efforts) when you crossed the threshold and your muscles ceased working.

So, realising that the burn I was feeling in my quads was a sign that my body was working well was comforting. But what was making me feel fatigued, sometimes earlier in a training session than at other times, and how could I convince my brain that I wasn’t about to keel over? Was it psychological I pondered…. for all of 5 seconds. I already knew the answer to that!


We have to train our bodies to become fit ad strong, we have to push ourselves so that at a basic cellular level our bodies adapt and become more efficient. But what else affects our ability to reach inside ourselves, grit our teeth and push on?


Recently I ran a marathon and decided that I would try a slightly new approach. I would wear my heart rate monitor, but I would only consult it if I was getting into trouble or the fatigue was approaching faster than I anticipated.

I pondered, would HR feed back subconsciously increase my perceived exertion and make me feel fatigued, if I was telling my self I had reached my HR limit, or could I acknowledge the limit but dismiss it if my body felt good? Was my HR going to dictate my fatigue and performance or was I consciously going to override this feedback and choose to ignore it?


I knew that he majority of my training runs had been done with an average heart rate reserve of 81- 83% ( above the theoretical threshold) and I hasn’t spontaneously combusted. Or walked. I knew that all my half marathons were raced at a higher heart rate than this, and I hadn’t hit “threshold”. Still I deliberated. What if I dared to push this a bit, ignoring the numbers and slightly pushing the boundary, acknowledging the numbers but crucially, listening more to my body than the display on my wrist.


I decided it was time to stop being a slave to the technology and listen to the greatest machine of all, my body. I was confident that this approach would work, but I was not absolutely certain. What I do know is that the way I feel and what I think can make or break my performance. This much I have learned and am now absolutely certain of. Above all other things that can affect the outcome of my race, if I have done the training, is my state of mind.


As I stood at the start I met a young girl who told me that she never ever ran with a watch, or any kind of monitor. She said she was new to running with only 2 years experience and had run Paris last year in 3:31, by listening to her body. This cemented my plan. Could it have cemented my downfall….? No, I don’t think so, why? Because I believed in what I was about to do. And therein lies the answer. A belief and a confidence in my ability. I knew I could cover the distance and I knew I had the endurance because my coach told me so. I knew I could push my heart rate slightly higher than I had in other marathons because I’d done it in training runs and I was drawing confidence from my experience.


Yes, I was nervous; there is always uncertainty with races– will the strategy work or will it blow up? Will you suffer with gastric issues, will you collide into someone? Nothing is a given. But I have learnt to try and expect the unexpected and plan for those times, to have confidence that I can cope with them.


After about 4 miles I began to suffer with bad chaffing from my heart rate monitor. Even when I was ignoring it it was trying to draw my attention to it! I knew I had to sort this or it would consume me and my focus would be shifted, I was beginning to perceive it as a problem and I had to tackle it before it affected my race. I tucked my sports bra up underneath it to stop it rubbing, and glanced at my watch – my heart rate was 82%. I felt good and I carried on.


After about 9 miles my pace began to fade. This was not an issue. I expected it and so didn’t worry. I usually do the same in training sessions and I have learnt to ignore any slowing and be confident that the early fast miles are banked to counter the later slightly slower ones. Fatigue arrived, I acknowledged but I knew I wasn’t going to stop, I had fleeting moments of wanting it to be over, but not of wanting to stop.


My heart rate fluctuated around 82-83% in the first half of the race, increasing steadily in the second half as I pushed on and refused to stop. In the last 2 miles I got angry with my body and wow – this really worked – why did I get angry? Because I’d trained, I’d got out of a warm bed to run in the wind and I was damned if I was going to slow completely. So did I run a marathon at threshold? No, I didn’t, because lactate threshold doesn’t exist, but the ability to train the body and the muscles to work harder at a higher intensity does. (By writing this I am not in anyway questioning the value training by heart rate. I train using heart rate parameters and I believe it works for me).


I know that the desire to slow is a result of the fatigue I feel in my head. Perceptions have the power to make or break. I have learnt to relax and accept that this is how my body works. It makes me push harder because I am fighting against that cautious sloth on my shoulder that doesn’t want me to injure myself so tells me to slow down, that i’m very tired. My conscious self argues back, that its ok, you’re lazy, you know what? I am just going to carry you around. Its no problem.

Hurting is not a nice experience and it doesn’t get easier, we don’t always get faster or go further either, but the hurt gets more bearable. We become hardened to it and we expect it and accept it. And because of that it is less frightening, we can learn how to deal with it and how to manage it. Mentally we become tougher.




Its ok to follow your heart, but don’t forget to take your head with you.


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