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Oddly enough, when you are moving parts of your body, your ability to detect an external stimulus on those parts of your body is diminished. Thus, a small vibration that you might easily be able to detect if you hand was sitting at rest would be very difficult to detect when your hand was in motion. This type of sensory suppression is known as 'tactile gating', and is thought to be a consequence of a central system designed to maximise your ability to detect stimuli which are not self-generated (so, turning off the detection system during motion, when you receive lots of irrelevant peripheral stimulation, seems a sensible option). Previously, this effect had only been demonstrated in simple single-joint actions where haptic feedback would not be of any help with the task. My first study on this topic was to demonstrate that this effect also occurs in goal-directed manual reaching tasks, where haptic input presumably plays at least some small role in task success. Interestingly, this effect occurs some 200ms before movement onset. However, our more recent work has shown that this suppression is modulated by the task demands at the measured site, such that there is far more gating at non-relevant locations (e.g., the forearm) than relevant locations (e.g., the index finger) during precision grips. How this effect relates to other aspects of force perception is an interest I've sadly not had much time to pursue in recent years, but would love to study more thoroughly.
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