EMG Assisted Fitting

EMG Assisted Fitting

Surface EMG (electromyography) measures the electrical conduction of skeletal muscles.  Important to note is that there are two types of EMG — “Surface” and “Needle” — the latter of which, hurts.   I use sEMG (surface) for bike fitting and pedaling technique training (of course).

There is much debate over the accuracy of sEMG data, and I agree that needling a muscle provides superior data to the sEMG sticky-sensor.  Lucky for us, technology has improved significantly during the past decade.  Surface EMG is a steadfast component in motion analysis studies, especially when integrated with 3D markers, force plates, and the ability to design custom protocols.  I use the BTS Bioengineering Sports Lab, which is designed for medical-grade application, and used at the Mayo Clinic,  NASA , Columbia University and the Italian Olympic Center.

Here is a link:

bts-logo

Applications?

Muscle Fatigue Testing:

Wind-tunnel testing is essential to optimal aerodynamic positioning for  Time Trialists.  Given a specific distance of travel (event), one can monitor muscle recruitment patterns in different positions.  Simple math can determine whe optimal ratio of aerodynamics to position.

Postural Analysis:

2D, 3D, Video fitting is limited by the fact that the prescribed “optimal” angles are, in fact, based on averages. The accuracy of these  measurement devices is great, but only in relation to muscle function.

Leg Efficiency/Balance:

There are numerous devices that measure leg pedaling efficiency, but results are frequently skewed due to the contralateral leg effects inherent to fixed crank-arms.

Electromyelography measures muscle recruitment between the right/left legs and anterior/posterior leg(s).

Injury Diagnosis and Treatment — Bike Related:

Low back and Illiotibial issues (among many others) are amenable to position changes.  Improvements are measured objectively, when monitoring with sEMG.

Pedaling Efficiency Training:

I use position adjustments, verbal/physical cues, and biofeedback to help riders improve muscle recruitment patterns that are conducive to effective pedaling.  

Latency-testing at follow-up appointments, suggests the ability to retain/store these patterns in post-fit conditions.

This is an example of the EMG data.  Notice the low amplitude (start), poor base-line, and quality of the firing patterns.  We are looking for single, sharp, peaks and valleys, of equal height and duration.  Here I am using a physical (resistance) cue to shape increase firing.

This is the same customer after five-minutes.  Amplitude suffers training effect, but the muscle function is far more effective/healthy.