Q Ive picked up an injury thats likely to stop me running for at least a month, but as I desperately want to keep up my cardiovascular fitness levels, Ive decided to cycle to and from work a round trip of 25 miles. How can I best make use of my daily commute? Can I replace interval sessions, hill work and long runs on my way to the office?A The first obvious thing to remember is that bike miles and running miles arent equivalent. If you were to run at, say, eight miles an hour, youd use about three to four times as much energy as you would if you cycled at the same speed. Depending on your fitness, youll find that youll be able to cycle at between 150 and 250 per cent of your running pace. So if you usually run at seven miles an hour (eight and a half minute miling), you should be able to ride at between 10.5 and 17.5mph. But while bike miles burn less energy, you will be able to train for longer periods and repeat the mileage without the associated leg tiredness that running produces.
The types of training possible are the same; only the muscles trained and the speeds reached will differ. For example, you might do sets of three-minute repetitions, which equates to 1200-200m on the bike. (The fitness benefit equates to about 600-1000m in running intervals
Rather than using distance or speed as your guide, it might be worth using heart rate instead. Your heart rate will tend to be lower for the same effort, when biking: you should take 5-10 beats away from your running heart-rate levels to get a reasonable cycling heart rate. For example if you run intervals at 165bpm, on the bike, you should aim for 155bpm.
Of course, balancing cycling and training isnt always easy during the rush hour, and safety has to be the most important factor. Racing fast through traffic to hit your interval time and increase your heart rate isnt a great idea. Instead:
(1) If its safe, sprint away from junctions, lights and roundabouts. The emphasis is in getting from zero to interval pace as quickly as possible.
(2) Plan longer rides on your homeward journey so you can boost endurance and explore new routes.
(3) On hilly routes, use the ascents to do a moderate interval. Rise out of the saddle to boost leg power and climbing finesse. Use the flats to prepare for, and recover from, those climbs.Joe Beer, triathlon coach and exercise physiologist