An SRM (an acronym for “Schoberer Rad Messtechnik,” which loosely translates as “Schoberer’s cycling measuring technique/technology”) consists of a strain gauge mounted inside the crankarm spider, and a monitor mounted on the handlebar. Readings are picked up via a sensor like a standard bike odometer. It’s not yet available to the public.
Similar computers were developed by Look and Power Pacer but were never widely used. Perhaps the biggest obstacle was the conservatism of European pro team directors, who are wary of new training techniques. A more practical reason is the weight penalty. The SRM adds 250 grams to a bike. Another is price–more than $5,000. Also, supporting software for tracking performance in a dizzying array of charts and graphs has only recently been developed.
Despite the expense and complexity, Carmichael and sports biomechanist Jeff Broker, Ph.D., believe the SRM could become the next universal training tool. (Other cycling scientists and some riders, such as Greg LeMond, agree.)
“We initially used it to determine the most aerodynamic positions and equipment,” Broker says. “But it also allows us to measure actual improvement by tracking power output in watts at a given heart rate.”
For instance, suppose a rider covers a course in 10 minutes at an average heart rate of 170 bpm and an average power output of 300 watts. A month later, an identical ride takes 11 minutes at the same heart rate, but the cyclist produces 330 watts. If you look only at elapsed time, you might think the rider lost power. But direct measurement of watts tells the true story. He was actually stronger. There must have been harder headwinds or some other impediment on the second ride.
Carmichael cites another example. “The SRM allows coaches to record actual power output in a competitive event and find out exactly what a rider must be capable of to win,” he says. “If we know a road race requires 10 minutes at 800 watts, 2 hours at 250 watts and another hour in between, we know what we have to accomplish in training. And, we’ll have a physiological profile of a successful racer.”
- In some events, particularly track, the measurements are exactingly precise. In the 4-man team pursuit, the SRM revealed that the lead rider puts out about 600 watts. When he swings to the top of the velodrome banking and drops to the rear of the paceline after his pull, watts drop to 350. Drafting in the third position, the rider’s power output declines to 250. In the second slot it rises slightly.
- With this information, coaches can devise a set of intervals for training that exactly mimic the power demands of the event.
- The SRM can even judge riding technique. For instance, if a rider edges above 400 watts at the back of the paceline, “he probably used too much energy catching back on and needs to smooth out his exchange,” Carmichael explains.
- Finally, the SRM is a great motivational tool for indoor training. Information on heart rate, power output, and cadence can be displayed on any IBM-compatible monitor. In Hartwell’s epic sprint session, this information acted as classic biofeedback, exhorting him to greater efforts.
Simulated competition could be especially important to riders who can’t race as often as they wish but want to maintain peak condition. Hartwell is ignoring the criterium circuit to concentrate on training for a few kilometer events. “The feedback helps,” he says. “I’m not racing much this year, but I can compete against my past performances and still stay sharp.”
It sounds exciting, but how long before the technology trickles down to benefit you? No one is sure, but Carmichael guesses it will be some time. Even at the elite level, the U.S. lags behind cycling kingpins such as Germany and Australia in measuring and developing power. Germany has an estimated 30 SRMs in operation. The OTC has 1. This means that many aspiring Olympians–let alone weekend century riders–don’t have a profile of their power.
But Carmichael isn’t daunted. “We’re going to get more units,” he says. And he believes that someday SRM-like devices will be available–and affordable-for fitness riders. Until then, we non-Olympic pedal pounders can light up the roads and trails with one of Carmichael’s 4 power-specific workouts