j_young_80
08-12-2009, 03:43 PM
What's the matter? Experience says you can time trial at a 22-mph (35.4-kph) average speed on a flat and windless course. And doing it requires a heart rate of 160 bpm. Okay, so you enter the local 10-mile (16.1-km) TT and during the second half you see you heart rate rise even though your speed doesn't. By the end you're up to 170 bpm -- near your maximum. Why did this happen?
Here's help: You're experiencing a common phenomenon called "cardiac drift." If researchers put you on a stationary bike and set the resistance to elicit a heart rate of 80% of max, after about 30 minutes your heart rate will creep up to 90% even though you're not generating extra power. On the road, it's not uncommon for something similar happen in a time trial.
Cardiac drift is caused in part by dehydration. But merely staying hydrated won't eliminate a rising heart rate because you can't absorb enough fluid from your stomach to keep up with the deficit. Muscle fatigue also contributes, as do factors that science hasn't quite figured out yet. As a TT progresses, your heart must work harder to maintain the same power output from your muscles.
Here are 3 solutions:
Vary your weekly workouts. You can't prevent cardiac drift, but you can lessen its effects. One way is to stop making every ride a steady, time trial-like effort.
Here's an example for a typical training week in the season: Do 2 short rides quite easily at about 60-70% of max heart rate. Do one day of strong, steady riding at 85-90% of max. Do one or 2 interval days when you elevate your heart rate to 90% or above for short periods, alternated with easy cruising. The week should also include one long endurance day and one or 2 rest days off the bike.
Stay well hydrated. Use a sports drink and practice pouring it down on days when you make hard efforts. The more you accustom your stomach to accepting the drink, the faster it will empty and send the fluid to the cells where it'll help reduce cardiac drift.
Start slow, finish fast. An effective way to lessen cardiac drift in time trials is to maintain a moderate heart rate and power output in the first half, then increase intensity during the second half to cover the distance faster. This is called a "negative split."
For a time trialist riding the 40-km (24.8-mile) championship distance in an hour, the first 20 km might be ridden in 30:30 while the final 20 km is covered in 29:30. Of course, this would be in ideally calm air and flat terrain.
In cycling, you usually need to think in terms of power output because wind and terrain can make time splits meaningless. If you know you can average 250-255 watts for the TT, you might ride the first 35 minutes at 240 watts, then bump it up to about 265 watts for the final 25 minutes.
Here's help: You're experiencing a common phenomenon called "cardiac drift." If researchers put you on a stationary bike and set the resistance to elicit a heart rate of 80% of max, after about 30 minutes your heart rate will creep up to 90% even though you're not generating extra power. On the road, it's not uncommon for something similar happen in a time trial.
Cardiac drift is caused in part by dehydration. But merely staying hydrated won't eliminate a rising heart rate because you can't absorb enough fluid from your stomach to keep up with the deficit. Muscle fatigue also contributes, as do factors that science hasn't quite figured out yet. As a TT progresses, your heart must work harder to maintain the same power output from your muscles.
Here are 3 solutions:
Vary your weekly workouts. You can't prevent cardiac drift, but you can lessen its effects. One way is to stop making every ride a steady, time trial-like effort.
Here's an example for a typical training week in the season: Do 2 short rides quite easily at about 60-70% of max heart rate. Do one day of strong, steady riding at 85-90% of max. Do one or 2 interval days when you elevate your heart rate to 90% or above for short periods, alternated with easy cruising. The week should also include one long endurance day and one or 2 rest days off the bike.
Stay well hydrated. Use a sports drink and practice pouring it down on days when you make hard efforts. The more you accustom your stomach to accepting the drink, the faster it will empty and send the fluid to the cells where it'll help reduce cardiac drift.
Start slow, finish fast. An effective way to lessen cardiac drift in time trials is to maintain a moderate heart rate and power output in the first half, then increase intensity during the second half to cover the distance faster. This is called a "negative split."
For a time trialist riding the 40-km (24.8-mile) championship distance in an hour, the first 20 km might be ridden in 30:30 while the final 20 km is covered in 29:30. Of course, this would be in ideally calm air and flat terrain.
In cycling, you usually need to think in terms of power output because wind and terrain can make time splits meaningless. If you know you can average 250-255 watts for the TT, you might ride the first 35 minutes at 240 watts, then bump it up to about 265 watts for the final 25 minutes.