Jerking movement during the pedalling. This is seen quite commonly.
“Jerking” - It’ll improve over time
The issue we often see is, flexibility and strength on riders’ ankles. This is the main cause of “jerking”. When pedalling COGY, we have to lift our feet up, instead of going down like ballerina’s. Many people who use wheelchairs have issues with ankle flexibility and strength. Are your ankles soft enough to bend at least to 90 degrees? Are you able to lift up your feet and make sharper angle on your ankle?
The young man in this video used to have serious sore on his ankles and shins (the muscle to lift up his toe) after pedalling for 10 mins. However, after a few sessions, he seems to have gained strength. He can now keep on pedalling for more than 30 mins. You will still see clickings on his ankle, which is due to his effort to lift his feet up.
During the early days, it may be a good idea to support rider's ankles. One idea is this video. We tried using a shoe string. This worked well. By doing this, at least, rider’s ankles won’t get hurt from too much knocking.
How to test if the issue is mechanical or operational?
Get a person without any walking difficulties try pedalling. Does the pedalling still jerk? It usually doesn’t.
“Slipping” - Try not to..
Even I, as a COGY expert, with no neurological conditions, experience slipping of pedal, for example, when I try to pedal up a steep slope. In order for efficient pedalling, the angle, amount and the timing of the strength we put onto pedal have to be adjusted every moment. This is of course very difficult for people with neurological conditions, especially for people who has not peddled before.
One slipping in a while may be OK. But, if you force COGY to slip too often, then it may lead to gear breakage. The common conditions to break the COGY gear are soft sand, grass etc.
This is the example of broken gear. Pedalling keeps on slipping and does not engage.
Soon, gear will completely stop engaging, like this video.