The OP has symptoms and based on an internet search he concludes it might be TOS. Slidewinder blindly assumes that the machine is to blame, because that is his only steady "contribution" to this forum, IMHO completely disregarding the info the OP has given.p_b82 wrote: ↑February 2nd, 2023, 7:49 amI really don't want to feed you - and derail the actual advice being offered to the OP (even if I personally failed to comprehend what TOS was by being initially lazy in my response and thinking it was something else without fact checking myself)- as imo your points are not really related to TOS at all, one could have perfect alignment and still demonstrate this behaviour, as the wrist position during the rowing stroke probably has no impact on the thoracic area - if the OP's issue is due to that.
First of all, I don't know if the OP's assessment is correct. Self-diagnosis based on internet searches are known to be horribly wrong (please note, some sites are incredibly good though, typically being maintained by medical specialists). There are other conditions that can cause similar symptoms, and even when a neurologist is able to physically investigate the patient, there are several conditions which lead to similar symptoms that require a significant investigation before things can be excluded. There are some physiotherapeutic assessments for TOS, but they aren't sufficient to definitively conclude TOS. AFAIK, confirming a TOS diagnosis requires an echography/ultrasound/Electromyogram to be made of the shoulder. But another cause could be a slightly herniated disc around the C6 and C7, causing similar effects. To confirm such diagnosis, you need an MRI of the neck. But as the OP indicates the effects are gone with rest, AFAIK, a herniated disc is unlikely (as it typically takes 6 months to heal) and even TOS is as it normally takes 6 weeks of rest before recovery. But visiting a doctor or physiotherapist when the pain returns after a return to rowing might be wise, to exclude sources definitively.
Secondly, as you and James adequately point out: the clear relation between handle design and symptoms/condition isn't there. I know some people who row half and full marathons at least twice a week, some rowing 1500K a month and those people should have issues as well simply due to their prolonged exposure. Although not impossible, it does suggest that something more is at play. For me, based on the info of the OP, the relation between a significantly increased training load and the symptoms is clearly there, as with the lower training load the symptoms were absent. It is the thing that changes, so the increased training load probably triggered something. It could be a reduced bloodflow due to cramped muscles (which can be a reaction to training when recovery isn't complete), or similar. Especially when people have an active lifestyle, like the OP indicates, the cardiovascular system isn't the limit to overtraining: it typically are the joints/muscles that aren't used to the many repetitions and don't get the time to adopt before the next training, resulting in a functional degradation.