The five per cent rule is a simple way to minimise your risk getting a running- induced injury: Keep your mileage low if your current body weight is more than five per cent over your ideal weight.
With each kilogramme of body weight you are loading three to four kilogrammes of force across your back, hips, knees and ankles. For example, say your ideal racing weight is 68kg. If you are hitting the scales at 71 today, you’re five per cent over goal racing weight. Now take those three kilogrammes and multiply them by three kilogrammes of force: You are loading nine kilogrammes of force across your joints. In a word, ouch!
Get yourself strong and in shape before you start logging serious running miles. I suggest biking, swimming and strength training with only two or three runs per week until you are close to your target weight.
For strength building, I’m a huge fan of the plyometric jump squat: Start with your legs wider than shoulder- width, squat down lower than knee level and jump straight up into the air, making sure that both feet leave the ground. Do seven to eight sets of 15 reps three times per week to build strength, promote cardiovascular fitness and help with the spring weight loss. If you aren’t panting like a dog, you aren’t working hard enough.
If you can build your cardiovascular fitness and strength without loading too much force across your joints, you’ll be happier and healthier come July and August.