Surface EMG and Bike Fitting

Surface EMG and Bike Fitting

Surface EMG (electromyography) measures the electrical conduction of skeletal muscle activity.  It is important to note is that there are two types of EMG — “Surface” and “Needle”.   I use sEMG (surface) for bike fitting pedaling analysis and biofeedback training.

There is much debate over the accuracy of sEMG data compared to Needle EMG.  and I agree that needling a muscle provides superior data, but this type of testing is typically reserved for medical applications/nerve studies, where a person is not moving.

Technology has improved significantly in the past decade and the ability to smooth and filter sEMG signals provides significantly more accurate data .

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.



Contemporary Applications for sEMG:

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 power.

Postural Analysis:

2D, 3D, Video fitting is limited by the fact that the prescribed “optimal” angles are, in fact, based on averages,  representing the most basic biomechanics analysis called kinematics.  The accuracy of these measurement devices is great, but utility is poor absent the force(s) producing movement, called kinetics.

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’ve designed biofeedback protocols to help riders improve muscle recruitment patterns that reduce counterproductive pedaling.

Glute Medius Training Example

Pre-Exposure:  Waveform demonstrates cross-firing artifacts and variability



Post-Exposure:  Waveform demonstrates isolated contraction and consistency.