Endurance

Bonking, hitting the wall, and visits to the sleep monster are all activities that endurance athletes want to avoid. Akbar Lalani explains

Training for an endurance race is similar to revising for a medical school exam--you have loads of good ideas and strategies well in advance. You then spend most of your time procrastinating and dabbling in some work. Finally, one day, you realise that time is running out and that you really better get on with things. So what is it that endurance athletes think about when training for and competing in events? Although not a natural athlete, I did manage to train for and successfully complete the world's toughest endurance race, the Marathon des Sables. Along with 700 other runners, I survived the 150 mile seven day ordeal in the Sahara desert, where temperatures peaked at 51°C.

Many endurance athletes develop borderline obsessive-compulsive behaviour patterns when it comes to their training. With so many parameters to control, life can become a series of numbers, times, weights, repetitions, sets, heart rates, calories, and hours of sleep, to name but a few. A typical week during my 18 month training schedule consisted of 30 hours training, 60 hours sleeping, 28 000 calories (117 MJ) consumed (split into six meals a day), and the odd hour or two at medical school.

The build up

A runner's most powerful tool for monitoring progress during training is the heart rate monitor. Many cardiac adaptations occur as a response to training load. Athlete's heart, a condition encompassing the simultaneous increase in the volume of the ventricles and the hypertrophy of the heart wall, can be detected in many athletes who typically spend more than 15-20 hours a week training. Other changes occur including an increase in stroke volume, and this leads to a decrease in heart rate at a given exercise load. The effect of training is to increase the efficiency with which the heart can provide the required output of blood. Ultimately this translates as a lower resting pulse. Through training, my resting heart rate decreased from 64 to 48. Monitoring the heart rate for a given exercise load allows athletes to chart their improvements. It also gives them a powerful method of splitting training sessions into "hard, medium, or easy" according to a predetermined percentage of their maximum heart rate.

It would be fair to say that almost all body systems adapt to exercise loads. Spirometry tests show that endurance athletes have vital capacities, forced expiration volumes, and peak expiratory flow rates that are 10-15% above their predicted normal values. Trained athletes can breathe more deeply and efficiently and have lower resting breathing rates. Haematological manifestations of exercise include an increase of up to 1.5 litres in circulating blood volume, although the relationship between plasma and blood cells seems to stay contant. This allows an increase in total circulating haemoglobin (and hence oxygen carrying capacity) without the problems associated with an increased haematocrit.

I have heard it said that successful competition in endurance events relies upon the sum of what the athlete puts into their training, sleeping, eating, and their psychological preparation with each part being of equal importance. A high training load requires a greater than normal calorific intake. Sadly, this does not mean eating anything you can get your hands on. Most athletes will consume a normal balanced diet but with a higher total calorific intake. They will consume enough carbohydrate to replenish their glycogen stores and enough protein to encourage muscle regeneration and hypertrophy.

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Bonking

Training will increase the body's capacity to store energy--muscle glycogen stores can almost double from 250 g in an untrained 70 kg man to 400 g in a trained man. Even with this increase, the stores are limited to about 8.4 MJ of glycogen. So what happens when this store runs out? Bonking or "hitting the wall" can strike athletes of all ages, capabilities, and disciplines. Gluconeogenesis in the liver can only produce about 54 g an hour, and this supply is exhausted after about two hours of continuous load. The starving muscles look elsewhere for energy. They begin to cannibalise surrounding muscle tissue to release energy from amino acids. This will obviously lead to much quicker fatigue, muscle damage, and greater soreness the next day. There is however one saving grace--fat--free fatty acids to be precise.

Free fatty acids are fast becoming the latest research driven craze in the endurance world. High insulin concentrations during the first 30 minutes of exercise will prevent free fatty acids from being used as a fuel source, but, after this time, when insulin concentrations decrease, free fatty acids become the prime source of fuel during aerobic exercise (lactate being another inhibitor). Training your body to become a more efficient fat burner requires low intensity long duration exercise. During my training, I found that the best way of doing this was to run first thing in the morning on an empty stomach and, after about half an hour, consume a commercially available concentrate of free fatty acids. A word of warning though: it does take getting used to and on several occasions the cocktail left my body in a quandary as to which way it wanted to get out. The other advantage of free fatty acids--especially for a race such as the Marathon des Sables, in which you have to carry all the food and equipment--is that they are a dense energy source. An equivalent mass of glucose powder gives about a third as much energy. To prevent hitting the wall during the race, I consumed a total of 153 MJ, with about a third of that from fat.

You may be mistaken into thinking that exercise is always good for you, but when load levels reach extremes, such as 100 km runs, blood biochemistry can be altered to startling levels. After six hours of running, cortisol levels can reach 1200 nmol/l and serum urea (from the breakdown of muscle proteins) can rise as high as 16 mmol/l. Based on blood results alone, a marathon runner might be admitted to a coronary care unit as creatine kinase concentrations rocket to 10 times normal. Aside from biochemical changes, prolonged exercise has grave consequences on biomechanical systems. Joint destruction and early onset osteoarthritis are common in long distance runners as are bone pathologies such as shin splints and stress fractures. Shin splints and stress fractures became the bane of my race preparation. It was a huge blow to develop a tibial stress fracture just eight weeks before the race, especially as the recommended treatment was 10 weeks without running. It was decided that under the circumstances, eight weeks off running, a lot of cross-training in the gym, and a family pack of paracetamol, ibuprofen, and some tramadol would be the best management protocol.

Sand and madness: the Marathon des Sables

The sleep monster

To generalise an athlete's techniques for psychological preparation would be impossible. Preparation is an organic evolving system that encompasses the athlete's goals, previous achievements, and personality. Just as there is variability among people, so too will there be changes from race to race as the athlete determines what works for them and what does not. A small number of the "demons" that an endurance runner may have to deal with are heat, exhaustion, blisters, pain, and general feelings of wanting to give up. A particularly interesting phenomenon that is pertinent to races run over consecutive days and nights is known as the "sleep monster." It strikes people without warning and causes the body to literally shut down and fall asleep. Athletes have been known to fall asleep mountain biking or even running. Treatment is simple--sleep; even 15 minutes will keep the "monster" at bay for several more hours. All these difficulties need some degree of mental preparation if they are to be overcome. I achieved my most useful mental conditioning by chance. During the weekends I would drive up to the Brecon Beacons--a notoriously beautiful but bleak and rugged mountain range in Wales--and complete my longer training sessions ranging from four to 10 hours. The terrain was rocky and boggy and it rained continuously. Water and sometimes snow was often more than ankle deep. Learning to turn my mind off to the conditions around me was certainly my saving grace in the harsh environment of the desert.

A cup of coffee

Finally, race day arrived. I finished my warming up and stretching, drank my cups of cold coffee (caffeine provides mild improvement in aerobic exercise), and, while sizing up my fellow runners, I asked myself why on earth I decided to take on the toughest race in the world as my first marathon. I resigned myself to the fact that I was here and that I may as well give it my best and put all my training into practice. Spurred on by the soundtrack of Gladiator, I cross the start line, confident that each of my body systems has been primed to play its part in enabling me to survive and to cross the finish line.