Contributions and co-ordination of individual fingers in multiple finger prehension.
Level 4 - case-series / case-control
Laboratory experimental biomechanics study in healthy volunteers (Level 4 by design analogy).
PubMed 7758447 · doi:10.1080/00140139508925183
What was done
Ten participants performed precision grip lifting tasks using a force transducer-equipped apparatus. Individual finger grip forces were continuously recorded across three object weights (200 g, 400 g, and 800 g), two surface textures (plastic and sandpaper), and three grip configurations (five-, four-, and three-finger grips).
What was found
In the five-finger grip, individual static force contributions were 42.0% (index), 27.4% (middle), 17.6% (ring), and 12.9% (little finger), remaining consistent across all weight and friction conditions. Higher surface friction (sandpaper) led to faster lift initiation and an approximate 40% reduction in total required grip force compared to plastic. Fewer fingers increased total grip force exertion. In the four-finger mode, relative force shares were 42.7% (index), 32.5% (middle), and 24.7% (ring); in the three-finger mode, shares were 43.0% (index) and 56.9% (middle), showing that index finger contribution remained fixed while the middle and ring fingers compensated.
Why it matters
These findings suggest the central nervous system uses a single common scaling factor to coordinate multi-finger forces for light loads, with the index finger playing an invariant primary role.
Limits
The study tested a small cohort of 10 participants, evaluated only static prehension of light loads (up to 800 g), and did not examine dynamic handling, hand size differences, or clinical hand impairment.
Cited by
- supports The deep forearm flexors running into the fourth and fifth fingers are the weakest and least resilient to heavy gripping load.