Chemistry now: chemistry and sport

This resource looks at the chemistry of aerobic and anaerobic respiration and explores how athletes can manipulate (legally!) the chemistry of this process to their advantage by monitoring the concentration of lactic acid in their blood.

Chemists have contributed to these improvements in sports in a number of ways. For example, the design of improved materials for clothing and equipment – eg poles for vaulting, spikes for running and even the track itself. Chemists are also involved in devising and monitoring the best methods of training for particular sports. One example of this is the development of a performance test called the blood lactate threshold which helps endurance athletes such as marathon runners – to train and prepare for competition and even helps them monitor their performance during an event.

To understand the blood lactate test, we need to know something about the chemistry of how our bodies convert the chemical energy in our foods into mechanical energy, which makes our muscles contract. The energy required for muscle contraction comes from a molecule called adenosine triphosphate (ATP, Fig 1). In ATP, an organic (carbon-based) group called adenosine is attached to three phosphate groups. The phosphate groups are involved in the energy storage. The loss of one of the phosphate groups produces adenosine diphosphate (ADP) and gives out 30 kJ/mol of energy.

This reactionsupplies the energy used to make our muscles contract. Surprisingly, we have only a relatively small amount of ATPin our muscles at any one time – even Olympic sprinters have enough for only two or three seconds of effort. So how can a sprinter complete a 10 second 100 m race, never mind a marathon runner keep going for over two hours? The answer is that ATPis regenerated. The above reaction is reversible and phosphate is re-attached to ADPto make ATP. This requires an input of 30kJ/mol of energy. The energy for this comes from the breakdown of food molecules carbohydrates (such as glucose), fats and proteins. The primary source is carbohydrates. These molecules store a great deal of energy (a mole of glucose (180 g) can release about 3000 kJ when reacted with oxygen). Our bodies release this energy gradually via the ATP/ADPcycle.

Glucose is stored in the muscles as a carbohydrate called glycogen, which consists of many glucose molecules linked together (Fig 5). Some endurance athletes make sure that they have a good supply of glycogen for an event by ‘carbohydrate loading’. They eat a lot of carbohydrate (rice, pasta, bread, potatoes etc) for a few days before an event.

Our bodies have two ways of releasing the energy in glucose molecules – both processes are called respiration. The first is called aerobic – ‘with air’respiration and uses oxygen to ‘burn’the glucose to carbon dioxide and water.