My overall goal is to measure the power produced by the captain and stoker during a 45-minute training session. This is part of a research study I will be proposing to determine the effects of tandem cycling on the motor symptoms of Parkinson’s disease patients. In reality, it is not tandem cycling per se, rather rate of cyclic activity that I will be testing, we are just using a tandem as the delivery of this cyclical activity. Cheaper than developing a machine driven cycle with feedback features. The rationale comes from some observations that I have made with PD patients who have participated in RAGBRAI or other tandem rides with me. Essentially, when patients are exposed to a cadence (90-95) that is greater than what they can produce on their own (45-60), they tend to show an immediate and prolonged depending on duration of event (~1 month) improvement in symptoms. For more information see www.pedalingforparkinsons.org

Without going into too many details of the study, I am interested in measuring the power of the captain and stoker in two groups of patients: 1) traditional tandem set-up where pedals are time-locked and synchronized and 2) independent pedaling system on the tandem (e.g. Davinci like). While power is not the primary outcome variable, it will be necessary to measure as the amount of work performed between the two groups may differ and could be a potential confound.

After searching a bit, it seems the best, but expensive, option is to install a SRM powermeter for the captain and stoker. The polar and power tap systems will not work since they would not be capable of identifying power contributions of each person. Has anyone had any experience in actually measuring stoker and captain power separately?

I could not find any published articles that have addressed this issue.

Any comments/suggestions would be appreciated.

Jay

I think you better dig up Rube Goldberg to build the sort of contraption you'll need! let us kow how you fare. SOunds interesting.

I am not familiar with the mechanical workings of the power recording systems, but I think, from what you're saying, is that one variety must work off of an individual crankset (and is expensive), while the other somehow uses the net power delivered to the drivetrain as a whole.

I am pretty much stating the obvious, but do consider that it may be possible (at least in principle) to install one of each variety, with the difference being the power produced by the second person.

Good luck!
-Greg

Sounds like quite the research project and have no solution for you.
Have trained with a 'parkie' for a couple months to get ready for the 33 mile event in the El Tour de Tucson 2 years ago. She was not a cyclist but with twice weekly training rides we got her from doing five miles to riding the 33 miles in 2 1/4 hours (including one flat tire). She was just awesome!
Good luck with the 'parkie' research!

Sounds like quite the research project and have no solution for you.
Have trained with a 'parkie' for a couple months to get ready for the 33 mile event in the El Tour de Tucson 2 years ago. She was not a cyclist but with twice weekly training rides we got her from doing five miles to riding the 33 miles in 2 1/4 hours (including one flat tire). She was just awesome!
Good luck with the 'parkie' research!

Rudy..I met you at the most recent El Tour, I was riding with a patient that day as well. His comment to me around mile 20 was, "I can drink with my left hand." I asked him why this was so surprising to him and he said "I am left handed and usually the tremor and bradykinesia are so bad I can't get the cup or bottle to my mouth." BTW...he was drinking while we were pedaling.

I thought about the subtraction method suggested in an earlier post; there seem to be some inherent noise and reliability problems with the other systems that do not make this feasible.

Jay

It might be worth your time to email Allen Lim, Ph.D. if you havn't already done so. He may not have published anything in this area (Parkensons) but his extensive research in power output over the last 5-6 years may have produced something useful to your project. He is currently connected with CycleOps PowerTap and advises a number of pros. Good luck!

It is a nice thing that Becky has going with folks with Parkinsons to ride El Tour. Volunteered to ride tandem for them but could not find a short enough stoker for our tandem, so ended up riding solo as Bike Patrol (another good cause).
Good luck with your research!

I recall seeing bicycle trainers in the gym that used automobile alternators as the exercise load, thus converting the cyclists' power output to electrical power. Electrical
power can be measured across a resistor load bank. Two alternators and chain coupling options might allow the measurements you're after.

Even using the best technology there's bound to be a few problems. Even when calibrated, with the most powerful team, the power meter,
every once in a while will tell you "hey, she's not pedaling". ;-)

As you point out, the power tap is not going to work because it would measure the total power of the team. Plus, power tap hubs are only avaliable in 130mm and 135mm spacing. However, I think its possible a Polar unit might work. They work off of chain tension. Thus measuring the drive chain would measure total team power, and measuring the timining chain would measure the captain's (and from the 2, the stoker's power can be calculated). Polar's unit is supposedly not as accurate as the srm's or the powertaps, but it might be adequate depending on your study parameters. If you have the funding however the SRM's would appear the way to go.