Wednesday, 12 January 2011

Grip strength is the best real life comparator for the ability score of strength


After some heavy statistics I argued that EGG was wrong (shock, horror) to equate Strength with the military press. He said that strength of 3 meant a maximum military press of 30 pounds, whilst 18 strength was 180 pounds. I argued that the military press is too variable in its performance and the range is beyond a 0-25 ability score scale. I promised to explore a better comparator = grip strength.

So here we go…

Grip strength is the best real life comparator for the ability score of strength

An ideal comparator would have a range of 0-25 (D&D ability scores) but adult humans would nearly 100% of the time fall between 3-18, with the average falling around 10.

Unfortunately a comparator for wisdom, dexterity, constitution and charisma seem unlikely. IQ and intelligence score seem to fit the bill, provided one doesn’t try and squeeze a normally distributed curve onto a 3d6 probability curve. See this post.

As per my previous post the world record for military press equates to strength of 50 (500 pounds) but even some body builder enthusiasts can military press only 100 pounds, which in the proposed system (pounds pressed / 10 = ability score) should be the average for a normal adult not a body builder.

Grip strength is how hard you grip and might be tested on a machine like the one pictured from: http://www.topendsports.com/testing/tests/handgrip.htm

Look at this table I found from a study by Virgil Mathiowetz et al (1985) Grip and Pinch Strength: Normative Data for Adults Arch Phys Med Rehabil 66:69-72


Right hand Performance of All Subjects on Grip Strength (pounds)
Age
Male

Mean
Low
High
20-24
121
91
167
25-29
121
78
158
30-34
122
70
170
35-39
120
76
176
40-44
117
84
165
45-49
110
65
155
50-54
114
79
151
55-59
101
59
154
60-64
90
51
137
65-69
91
56
131
70-74
75
32
108
75+
66
40
135
All male R hand
104
32
176
All male L hand
93
27
160
All female R hand
63
25
137
All female L hand
54
23
115

This is a remarkable table. I’m not going to talk about left hand and female strength but more is on the table above and even more in the article itself.
Instead, Look at the all male R hand grip strength.
Look at the range: lowest 32, highest 176.
Look at the mean: 104

If we said that the Strength ability score was grip strength in pounds divided by 10 then we would have a mean of 10.4, lets be kind and call it 10.5 which is the average of 3d6; and a range between 3 and 18.

WOW

What’s the world record?
Somewhat confusing articles as totally not my field but you have to love anything called “IronMind Captains of Crush grippers”

Perhaps 300 pounds+ =  strength 30+; which is above our target top of 250 pounds (25 strength). Difficult to say but that said I’m still pretty pleased with this proposal.

Have you noticed a flaw emerging in my recent posts.

If a 3 is really unplayable in D&D, what is a 3 strength or 30 pounds grip strength like? Is it unplayable? Because if it is playable I am shooting myself in the foot, big time.

If we go back to the article by Mathiowetz above, and look at his subjects: “Subjects were interviewed at shopping centers, fairs, senior citizen centers, a rehabilitation center (staff), and a university... subjects continued to carry on a normal lifestyle without restriction in their activity level because of a health problem.”

So what he tested was a range of healthy normal adults of all age ranges. In D&D they would all be considered combatants. Therefore a strength of 3 is probably playable if it is equated to grip strength.

A 3 might really represent -3 to hit, -3 damage. It sounds reasonable now.

So a big counter argument here to my own arguments.
That’s fine – no really – I’m exploring a topic; I have no agenda. And I’ve got more to say, which though doesn't help my original arguments, is really interesting - for a sad nerd such as myself.

You see if strength 3 (grip strength) is the mininum for healthy adults over the whole age range – what about unhealthy adults or children.

Have a look at this diagram for children from Ha¨ger-Ross C and Ro¨sblad B. (2002) Norms for grip strength in children aged 4–16 years. Acta Pædiatr 2002; 91: 617–625

Now it’s in Newtons, not pounds and we need to convert. 
1 Newton = 0.224808943 pounds force

100 Newtons = 22.4 pounds which is reached around 8 years old in boys and girls. (This could represent a strength of 2; non-combatant)

Strength 3, 30 pounds grip strength is 133 Newtons, which according to the diagram is reached around the age of 9-10 in boys and girls. Perhaps combatant, equal to the weakest of the elderly range found in the adult study above. Seems reasonable to me.

Strength 4, 40 pounds grip strength is 177 Newtons, which according to the diagram is reached around the age of 11 in boys and girls.

Strength 5, 50 pounds grip strength is 222 Newtons, which according to the diagram is reached around the age of 13 in boys and 14 girls.

Strength 6, 60 pounds grip strength is 267 Newtons, which according to the diagram is exceeded by age 14 in boys and girls.

Strength 10.5 (average value of 3d6), 105 pounds grip strength is 467 Newtons, which according to the diagram is reached around the age of 16 in boys but not yet in girls/women.

A 16 year old male hits strength 10 – I can live with this model.

Not only that but with this model one can interpret age effects on strength and also interpret  strength lower than 3 - not bad I think.

What do you think of Grip Strength as the best real life comparator for the ability score of strength?

1 comment:

  1. Wow, seems like it works really well!

    Aren't there standard measures of hand-eye coordination you could use for Dexterity?

    ReplyDelete