Heavy legs? Breathless? Can't keep up with your training partners? If you've put any recurring lethargy down to too much training and have carried on regardless, hoping that the fatigue will eventually, magically disappear, you could be in for a long wait. You could have anaemia, which requires some level of intervention.
Anaemia develops when the number of oxygen-carrying red blood cells in your body falls below normal levels. When you're anaemic, less oxygen is delivered to the tissues and you feel tired and breathless sooner than seems normal.
You may not detect symptoms for months, since anaemia can develop gradually and is difficult to recognise until it becomes severe. It also resists detection since there are many reasons why you might not be performing at your peak - the sheer effort of training in three disciplines while holding down a job and finding time for families is a particularly convincing one - and the symptoms can also be mistaken for other problems.
Common signs are lethargy and a dizziness similar to that caused by low blood sugar. Your friends may say you look pale and you may feel exhausted all the time - even after a good night's sleep. If these symptoms sound familiar, ask your GP for a blood test to measure your haemoglobin and ferritin levels. Ferritin is an iron-storing protein and this test can give a good indication of your body's iron stores.
If you're active, you may be more prone to anaemia. Heavy training can increase your iron needs by 1-2mg per day, since iron is lost in sweat and, in blood, from the urinary tract or gastrointestinal system of many endurance athletes. The repetitive impact of running may also cause red blood cells to break down - this is known as foot-strike haemolysis.
While the average man needs 10mg of iron daily, the average woman needs almost twice as much - 18mg per day for those of childbearing age. This is why anaemia is more common in women. It's easy to improve your iron levels by taking a supplement or asking your GP to prescribe ferrous sulphate tablets, but you should also look closely at your diet.
Strike a balance
A balanced diet should provide adequate iron but, in reality, when you're busy and training (and perhaps trying to lose some weight to improve speed), it can be hard to consume enough of the right foods. This is especially true for vegetarian athletes, as iron from fruit, vegetables and cereals is not as well absorbed as that from meat.
If you are a vegetarian, increase your iron intake by eating plenty of pulses and dark-green vegetables such as spinach, broccoli and rocket. A handful of dried apricots and cashews provides an iron-rich snack and is easy to grab on the go. To optimise absorption of the iron that you're working so hard to take in, avoid tea with meals and drink orange juice instead, as vitamin C increases the uptake of iron.
If you are anaemic, cut back on training while your condition is being treated. This may come as a relief after all those months of forcing yourself out of the door, onto your bike or into the pool even though you felt awful. It's time to listen to your body, so limit yourself to some gentle cross-training and one or two short runs.
After a couple of weeks you will start to feel more energetic and you can slowly increase your training. In a few months, you will be back to normal and, perhaps, faster than ever. It's a good idea to have your blood checked regularly and to discuss iron supplements with your GP.