Erik asks: Maybe you can comment on something I touched on regarding torso rotational strength and muscle failure. Let me back up a step and say that when doing sit-ups, crunches, etc that primarily work the rectus [abdominus], it’s easy to feel the muscle burn and, thus, assess that muscle’s level of strength. However, when my rotational abs are failing, there isn’t much of anything related to a muscle burn, just the inability to do the required work.
Therefore, these muscles are somewhat silent and it’s difficult to assess their strength and notice their failure. As another example, i’m doing some training sessions with a sledgehammer on a tire, and the same thing holds true – When I tire (excuse the pun), I’m not sore, just wobbly in the core.
Why the different feeling?
Alan: Paddling uses a combination of abdominal muscles; obliques (internal and external), transverse abdominus (wraps your torso like a wide belt), rectus abdominus. Abdominal muscles are very strong and extremely aerobic at the same time. This is a function of their role in both posture and abdominal cavity protection. These muscles also adapt very fast to stimuli, such as exercises, training, etc. As they all work together in paddling, I would suspect that the lack of fatigue Erik mentions (burning, aching, etc.) is probably due to fact the fatigue experienced in most paddling events we do is due to substrate depletion or long term metabolite accumulation (aerobic) as opposed to short term metabolite accumulation (anaerobic). Sprint kayaking (fast 200 and 500 m efforts in particular) will get you that burning sensation!
Muscular fatigue is accompanied by reduced force, reduced speed (resulting in reduced power), reduced range of motion, reduced endurance, and an inability to relax the muscle. This is due to an increase in muscular acidity (lower pH) which interferes with calcium binding properties. In the case of anaerobic exercise induced fatigue (relatively big intramuscular pH change), this may well cause localized burning sensations. If I remember correctly, low pH reduces calcium binding which inhibits relaxing which causes the discomfort (burning). The wobbly feeling (decreased core stability) is a direct consequence of the reduced abdominal strength/coordination.
Your regular crunches, sit up and the like do primarily work the rectus abdominus (aka six pack muscles) which have an action of bringing the sternum closer to the pelvis in a longitudinal axis (head to toes). If you add a transverse rotational component into your exercise repertoire you’ll strengthen your obliques and transverse abdominus as well. When I went to the gym regularly I did a standing and sitting cable pull exercise that was essentially mimicking the kayak pull, but I kept the arms and back muscles isometric (non-contracting) so as to load the rotational / postural musculature. Doing crunches where you rotate from side to side also work, likewise holding a medicine ball. Check out this link for some ideas.
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