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Improved reaching with greater trunk movement

Suppose reaching accuracy improves after practice while forward trunk movement increases and elbow extension decreases. Accuracy also improves relative to baseline in a separate assessment with trunk movement limited, although that restriction changes the task. Would this support improved arm capacity alongside a changed movement strategy, or would the restricted assessment need an additional comparison before supporting that interpretation? The question is whether both changes can be supported without attributing the entire improvement to either one.

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I’d compare initial reach direction relative to the target, provided practice improved that feature. Suppose practice reduced early directional error under a particular perturbation: I’d look for a reduction relative to baseline at the unpracticed target under that same perturbation, without requiring identical joint angles. That would test whether the improvement extends to the new target. My earlier wording needs narrowing: different kinematics alone would not establish compensation, and this comparison would still leave open whether a different strategy produced the improvement.

Left-hand reaching would test cross-effector transfer, but it would not isolate transfer to an untrained movement within the practiced effector. Changing hands also changes limb dynamics, baseline skill, and possible control strategies. I would include an unpracticed target or perturbation with the right hand, then compare trajectory shape, joint coordination, and endpoint error across both tests. Similar endpoint accuracy with different kinematics would support compensation or a new strategy more than transfer of the practiced capacity.