The L posture that most sit-in and SOT kayakers are accustomed to being forced into when they paddle diverges from the original Inuit kayak posture, in that these antecedent kayaker designed their kayaks with neither a backrest (lumbar support) nor footrests.
Backrest and footrests were initially adjoined to these watercraft by modern kayak designers and manufacturers to restrain the paddlers and anglers who use kayaks from shifting forward. However, the cost of this augmentation is that kayakers and kayak fishermen experience discomfort that eventually results in back pain, leg pain, leg numbness and an array of other issues.
The combination of footrests and backrest creates a frame against which your legs can push forward in order to inhibit you from sliding forward. Your legs have the most robust set of muscles in your body, and as a result of their pushing on the backrest, the backrest exerts a force back on you – that’s just simple physics. This results in an ergonomic nightmare for you as the user, because the majority of this pressure is exerted on your spinal column, a very sensitive region, especially in advanced age.
Basically, this position is named the L posture, dubbed so because your legs are forced forward in a manner resembling the letter, is abnormal to your body, as well as possibly harmful in the long term:
Anatomically, your spine is construed of rigid bones, separated by discs of flexible cartilage. This structure is optimal for supporting vertical loads and efforts usual to running, walking and standing up, but not for contending with horizontal pressure like that created by the L posture.
The above image demonstrates how this works: your own legs work against your back to support you in this posture while you’re paddling and fishing.
The worst of this is that you can’t adjust yourself to a different position because this is the sole position that sit-in and SOT designs will accommodate.
Despite designers’ and manufacturers’ attempts to alleviate this problem by cushioning their kayak seats, it is impossible to fully solve the problems created by this defective design in this manner because your spine in your lower back is the sole hard object between your pelvis and your rib cage, and no matter how much cushioning is added that’s exactly where the pressure will be focused.
Another complication generated by the L kayak posture is the vertical pressure on your tailbone and butt, as illustrated by this image:
The joint weight of your upper body with a portion of the weight of your thighs presses your posterior downwards, precisely in the region wherein your sciatic nerve is situated.
Here your legs cannot support this effort, but rather they do the opposite, and exasperate the problem.
This incessant pressure causes disruptions in the regular circulation of blood to your legs,which manifests itself as leg numbness and leg pain.
Additionally, it can also harm your lower back, as your legs push harder in vain, trying to change their position and relive the the pressure on the sciatic nerve.
This swath of problems elucidates clearly why so many people who use kayaks for touring and for fishing generally feel awkward in their kayaks, and why an abundant number of them suffer from back pain and back stress.
The L posture catalyzes fatigue, leads to leg and back pain, and all in all makes kayaking and kayak fishing an uncomfortable and is a disaster from an ergonomic design standpoint. The only way to fix this design flaw is to create a new design for fishing kayaks. So far the only solution to this problem is the W fishing kayak, and its new design.