Synching EMG data with Pedal Cycling

[Brad Dieter]

Biomch-l users,

I am conducting a research study examining muscle activations in cycling. I am looking for a way to synch EMG data to the pedal cycle. I am using a biometrics EMG device. If anyone has any suggestions I would greatly appreciate it! Thank you.

[Eneko Fernández Peña]

Re: Synching EMG data with Pedal Cycling

Hi Brad,

We solved this problem by coupling a rotational encoder to the crank of the ergometer and integrating it into the EMG data acquisition system. In this way, we were able to simultaneously measure EMG and crank angular position.
-Fernández-Peña, E. et al (2009), Training with independent cranks alters muscle coordination pattern in cyclists, Journal of Strength and Conditioning Research, 23(6): 1764-1772.
-Fernández-Peña, E. et al (2009), A maximal isokinetic pedalling exercise for EMG normalization in cycling, Journal of Electromyography and Kinesiology, 19(3): e162-e170.

A second option is to measure the crank angular position once in the crank cycle (for example with a magnetic device) and assume that crank angular velocity remains constant throughout the whole pedal stroke.

Hope it helps,

Eneko Fernández Peña
Department of Physical Activity and Sport
The University of the Basque Country

[Mark Corbett]

Re: Synching EMG data with Pedal Cycling

Brad,
We've gone for the simpler second option approach described by Eneko with a Biometrics Datalink/log. A reed switch pickup cut from a standard cycle computer is on the chainstay and cadence magnet on the crank. The reed switch briefly closes a relay powered by a 9V battery. The relay toggles the line input to the Datalink from ground up to 5V.
At present we are using an analogue input on the Datalink, mainly because we had the appropriate 4 pin LEMO connector available. A better option might be to use one of the digital inputs (6 pin) since this opens up some extra processing options in the Biometrics software.
It is not as precise as the encoder option but allows integration over pedal cycles and approximate angular determination.
I can send you a circuit diagram, pin-outs etc. if needed, alternatively contact Biometrics who are very good for technical support.

Mark
University of Worcester, UK

[Brad Dieter]

Re: Synching EMG data with Pedal Cycling

Eneko,

This looks like a great idea. Have you ever tried to use it on an actual bicycle? I am planning on conducting the trials on the participants actual bike. Do you have any thoughts on how to use a rotational encoder on an actual bicycle?

Brad Dieter
Graduate Student, Movement Sciences
University of Idaho

[Brian Schulz]

Re: Synching EMG data with Pedal Cycling

Brad,

If you're trying to put an encoder of some kind on an actual bike, you might try hacking this system:

http://www.revolights.com/

It's supposed to be available sometime in March and seems to have components that could easily adapted into a robust rotational encoder.

[Gannon White]

Re: Synching EMG data with Pedal Cycling

You didn't mention whether you have motion analysis available? I've got an undergrad doing her senior project on fore/aft cleat placement on biarticular muscle fatigue using an adjustable pedal. We are using Nexus and will define events as the high/low point of a marker placed on the lateral most point of the pedal as the cycle beginning/end.

[Eneko Fernández Peña]

Re: Synching EMG data with Pedal Cycling

Hi Brad,

We attached a small chainwheel in the crank that was coupled through a chain to an encoder mounted in the ergometer. But if you are planning to mount an analogous system on an actual bike, you will have to deal with several issues:

1-Of course, you should use an extensible crank in order to fit each rider’s crank length.
2-Mounting the encoder on a robust ergometer like an SRM or a Monark is definitively easier than mounting it on the frame of a bike.
3-If each cyclist will use his own bike, you will have to replace the modified crank every time… and the encoder too!
4-I bet that your cyclists will use different crankset and bottom bracket brands, which makes it even more complicated.

Therefore, if your goal is to distinguish different pedal strokes in order to calculate average EMG profiles or something like that, I’d suggest following Mark’s advice: it is accurate enough, you can use it in almost every bicycle and replacing it from one bike to another should be much easier and faster.

BTW, can I ask you which ergometer/roller/trainer are you planning to use? Maybe you could mount the encoder directly on the trainer instead of the bicycle frame, provided that no sway occurs between the bike and the trainer.

Eneko Fernández Peña
Department of Physical Activity and Sport
The University of the Basque Country

[Brad Dieter]

Re: Synching EMG data with Pedal Cycling

Mark,

I think I might try to go with this option for my pilot data and see how it works. If you have the circuit diagram and plans for it I would greatly appreciate being able to take a look at them and see if I can get some good results. Thank you very much for your input!

Brad Dieter
Movement Sciences, Biomechanics
University of Idaho