Body Mass Bias and
Occupational Relevance of
Military Physical Fitness Tests
Paul M. Vanderburgh, EdD
Professor & Chair
Department of Health and Sport Science
University of Dayton, Dayton, Ohio
BLUF
The Evidence Suggests:
Military Physical Fitness Tests
1. Are not potent indicators of performance of
typical, loaded military tasks
2. Impose a systematic bias against larger, not
fatter, service members
3. 1. and 2. are interrelated
Solutions
1. Scaled Values
2. Correction Factors
3. Balanced Fitness Tests (validation needed)
Military Physical Fitness
How Fitness is Assessed
(Army, Air Force, Navy)
Sit-ups or Curl-ups
Push-ups
Distance Run
Military Physical Fitness Tests
Army
Air Force
Navy
Upper Body
Muscular
Strength/Endurance
2 min Push-ups
1 min Push-ups
2 min Push-ups
Trunk Muscular
Strength/Endurance
Aerobic
Capacity
2 min Sit-ups
1 min Sit-ups
2 min Curl-ups
2 Mile Run
1.5 Mile Run
1.5 Mile Run
• Conducive to mass testing
• No special equipment needed
• Body weight is the primary resistance
Typical Physically Demanding
Military Tasks
Light Load Carriage
Heavy Load Carriage
Heavy Handling
Light Load Carriage
Heavy Load Carriage
Heavy Handling
Occupational Relevance
Free Carry and Stretcher Carry
Performance
Strongest correlates of free carry and
stretcher carry performance:
– High LBM to dead mass (FM + plus casualty
mass) ratio
– Standing broad jump
– Upright pull
(Bilzon Occup Med ‘02)
Load Carriage Determinants
Time to exhaustion on 18kg Load Carriage
(LC) test was:
– Not correlated with relative VO2max
– Positively correlated with LBM
Simplified aerobic physical fitness tests
(e.g., 2.4 km run) did not predict ability to
perform LC tasks
(Bilzon Occup Med ‘01)
Load Carriage Determinants
Absolute VO2max and LBM/DM were the most
potent predictors of %VO2max during heavy (40
kg) LC tasks
Absolute VO2max, LBM/DM, gradient, and load
accounted for 89% of variance in %VO2max
(Lyons Occup Med ’05)
PF Tests as Predictors of Military
Performance
Body size, muscle strength, and aerobic
fitness (L/min) differentially predicted lifting
and load carriage task performance
– Not push-ups
– Sit-ups generally weak
– Relative VO2max only for light load carriage
(Rayson Ergonomics ‘00)
PU, SU, 2MR
Military Task
Performance, 18 kg loaded
30m sprint to and from prone position
– Vertical jump and 2MR
400M sprint
– 2MR and vertical jump
Obstacle course
– Long jump, SU, vertical jump
Casualty recovery
– Body mass, vertical jump, and 2MR
(Harman MSSE (abstract) 2007)
Occupational Relevance and
Physical Fitness Tests Conclusions
Military physical fitness test performance is
generally not a potent predictor of loaded task
performance
LBM, LBM/DM, upright pull, 1RM lift, and
absolute VO2max are more predictive of load
carriage performance
Body Mass Bias
Body Mass Bias 101
Defined as the non-zero correlation
between body mass and a physical
performance measure
– Push-ups, sit-ups
– Distance run
– 1RM strength
Free of the confounding effects of effort,
body fat, or physical activity level
Theoretical basis
5K Run Time (sec)
Example – 5K Run
1600
1100
600
100.0
150.0
200.0
250.0
Body Weight (lbs)
data from Crecelius MSSE ’07 (abstract)
Comparison of Runners
5K Run Time (sec)
B is 8.5% slower than A
1600
B
A
1100
600
100.0
150.0
200.0
Body Weight (lbs)
250.0
Comparison considering body mass
Distance from the best-fit curve
5K Run Time (sec)
B is 8.6% faster than A
1600
B
A
1100
600
100.0
150.0
200.0
Body Weight (lbs)
250.0
Body Mass Bias Example
Powerlifting TOTAL
Total Wt Lifted (SQ+BP+DL, in kg)
1100
1000
900
800
700
600
500
40
60
80
100
120
140
Body Mass (kg)
(data from IPF website: www.powerlifting-ipf.com, 5/07)
TOTAL per M
Ratio Method
13
Total Lifted / Body Mass
12
11
10
9
8
7
40
60
80
100
Body Mass (kg)
120
140
TOT per M2/3
55
TOT/M^2/3
50
45
40
35
30
40
60
80
100
Body Mass (kg)
120
140
Scale Modeling of Body Mass Bias
A 25% increase in mass (exact replica):
• 1RM bench press is 16.0% greater
• VO2max (L/min) is 16.0% greater
• Run Time is 7.7% slower
• Push-ups and Sit-ups Reps are 7.2% fewer
Body Mass (M) and Strength
Theory
Strength α muscle CSA
Muscle CSA α M2/3
Therefore strength α M2/3
Fair comparison: 1RM/M2/3
(Astrand & Rodahl, Textbook of Work Physiology ’86)
M Bias and Strength
Evidence
Measure
Subjects
N
Exponents
Source
Powerlifting
Elite Women
36 world
record holders
0.63 - 0.87
Vanderburgh
MSSE ‘00
Powerlifting
Elite Men
30 world
record holders
0.49 – 0.68
Dooman
JSCR ‘00
Olympic
Lifting
Elite M & W
57
0.47*
Batterham,
JAP ‘97
Bench Press
M college-age
PE students
77
0.69
Markovic
EJAP ‘04
Leg Strength
Young M & W
401
0.67
Jaric JSMPF
‘02
• Exponents are somewhat variable
• Not all confidence intervals contain 0.67 but none contain 1.0 or 0
• *Found simple allometric model problematic
Body Mass and VO2max
Theory
VO2max (L) α M
Time α M1/3
VO2max (L/min) α M/M1/3
Therefore VO2max (L/min) α M2/3
Fair index: ml O2/(kg2/3.min)
(Astrand & Rodahl Textbook of Work Physiology ’86)
Body Mass and VO2max
Evidence
Subjects
N
M Exponent
Source
Young W
94
0.61 (LBM exp =
1.04)
Vanderburgh
MSSE ‘96
M, 17-66 yr
1,314
0.65* (LBM exp =
0.97)
Batterham, JAP
‘99
Young fit M & W
308
0.67
Nevill EJAP ‘92
M & W, 20-79 yr
440
0.65**
Heil MSSE ‘97
*Found the simple allometric model problematic
**Controlling for age, gender, %fat and SR-PA score
Body Mass and Distance Run Time (RT)
Theory
5K run speed (RS) α VO2max (ml/kg.min)
But VO2max (L/min) α M2/3
So RS α M2/3/M or RS α M/-1/3
Given that RT α RS-1
RT α M1/3
Fair index: RT/M1/3
(Nevill JAP ’92, Vanderburgh MPEES ‘07)
Body Mass and Distance Run Time (RT)
Evidence
Measure
Subjects
N
Exponents
Source
2-mile RT
M USMA
cadets
59
0.40 (FFW
exp. = 0.31)
Vanderburgh JSCR
‘95
2-mile RT
M USMA
cadets
238
0.26 (LBM
exp = 0.24)
Crowder MSSE
(abstract ’96)
5K Run
Young fit M &
W
308
0.33*
Nevill EJAP ‘92
5K Run
5K M Runners
56
0.30**
Crecelius JSCR ’08
• Exponents not diff. from 0.33 but diff. from 0
• *Indirectly calculated from: run speed = f(VO2max, body mass) equation
• **calculated using subjects with RPE > 16
Body Mass and Push-ups/Sit-ups REPS
Theory
Muscle force α M2/3
REPS α M2/3/M or M-1/3
Push-up, Sit-up REPS α M-1/3
Fair index: REPS.M1/3
(Markovic EJAP ‘04)
Body Mass and Push-ups/Sit-ups REPS
Evidence
Measure
Subjects
N
Exponents
Source
Push-ups
M USMA
cadets
238
-0.38 (LBM
exp = -0.28)
Crowder MSSE
(abstract ’96)
Sit-ups
M USMA
cadets
238
-0.26 (LBM
exp = -0.24)*
Crowder MSSE
(abstract ’96)
Push-ups
M college-age
PE students
77
-0.42
Markovic EJAP ’04
Push-ups
M college-age
PE students
77
-0.30
Markovic EJAP ’04
• Only exponent diff. from -0.33 and only slightly
• No studies on women
Run Time, Effort and %Fat
Age & Wt 5K Handicap Model
– Penalty for fat > credit for extra weight
(Vanderburgh MPEES ’07)
– With RT/M1/3, small remaining bias is
accounted for by RPE and % fat
(Crecelius JSCR ’08)
Body Mass Bias Conclusions for
Military Physical Fitness Tests
Military physical fitness test events favor lighter
individuals, independent of body fatness
Distance Run
– RT α M1/3
– Fair index = RT/T1/3
Push-up, Sit-ups
– REPS α M-1/3
– Fair index = REPS.M1/3
Implications/Solutions
Body Mass Bias Penalty - Navy
Male
Female
60 kg
90 kg
45 kg
75 kg
Maximum
Equivalent
Maximum
Equivalent
Push-ups 2 min
84 (100)
73 (85)
46 (100)
39 (80)
Curl-ups 2 min
101 (100)
88 (80)
101 (100)
85 (75)
8:55 (100)
10:12 (85)
10:17 (100)
12:11 (85)
300
250 (16.7%)
300
240 (20%)
Event
1.5 mi run time
Total points
(%diff.)
(Vanderburgh, Mil Med, 2006)
Body Mass Bias and Occupational
Relevance Connection
The more potent predictors of loaded military
task performance (LBM, LBM/DM, upright pull,
1RM lift, and absolute VO2max) tend to favor
heavier individuals (LBM, LBM/DM, upright pull,
1RM lift, and absolute VO2max)
Empirical and theoretical evidence suggests that
common physical fitness test events favor lighter
individuals
Middle ground?
Occupational Relevance and Body
Mass Bias
BW Resistance
Only
P’ups, S’ups,
Distance Runs
Light load carriage
over distance
Heavy load
carriage over
distance
Heavy equipment
or supplies
lifting/carriage
Fixed W
Resistance Only
Fitness tests
Most physical military tasks
Backpack Run Test
(Vanderburgh Mil Med ’00)
59 USMA male cadets
– Lean, fit
– Two-mile run times
Modeled effects of alterations in backpack
weight (BW) via ACSM equations on two-mile
run times
Backpack weights of 20-50 kg:
– No body mass bias
– Reflected load carriage weights expected of combat
support and/or combat arms service members
Eliminating bias may be congruent with
occupational relevance
Solution 1: Scaled Values
Subject Push-ups Body Mass
REPS.M1/3
A
67
80 kg
284.5
B
70
68 kg
281.7
Requires calculator
Creates strange currency
Solution 2: Correction Factors
Correction Factor (CF) : a dimensionless
number multiplied by raw score
– Based on body mass
– Uses weight standard (e.g., 50 kg)
Example: woman, 172 lbs, 16:08 RT
– CF = (125/172)1/3 = 0.90
– RTadj = 14:31
(Vanderburgh Mil Med ’07)
Correction Factors
Push-ups and Sit-ups
Women
0
1
2
3
4
5
6
7
8
9
120
1.00
1.00
1.00
1.00
1.00
1.00
1.00
1.01
1.01
1.01
130
1.01
1.02
1.02
1.02
1.02
1.03
1.03
1.03
1.03
1.04
140
1.04
1.04
1.04
1.05
1.05
1.05
1.05
1.05
1.06
1.06
150
1.06
1.06
1.07
1.07
1.07
1.07
1.08
1.08
1.08
1.08
160
1.08
1.09
1.09
1.09
1.09
1.10
1.10
1.10
1.10
1.10
170
1.11
1.11
1.11
1.11
1.12
1.12
1.12
1.12
1.12
1.13
180
1.13
1.13
1.13
1.13
1.14
1.14
1.14
1.14
1.14
1.15
190
1.15
1.15
1.15
1.15
1.16
1.16
1.16
1.16
1.16
1.17
200
1.17
1.17
1.17
1.17
1.18
1.18
1.18
1.18
1.18
1.18
(Vanderburgh Mil Med ‘07)
Correction Factors – Effect
(Vanderburgh Mil Med ‘07)
Solution 3: Balanced Tests
Balance of body mass bias via events.
Example:
– 1RM Bench press
– Distance run time
Logistics challenges
Has not been empirically evaluated
2005 Pump and Run
5K run time minus (30 x Bench Press Reps) = adjusted score
Bench Press weight a % of BW and age-adjusted
Despite intent, imposes a substantial body mass bias
Proposal: correction factors or everyone lifts the same absolute
weight
Adjusted Run Time (sec)
2000
1500
1000
500
0
35
60
85
Body Mass (kg)
110
135
Women
Men
(Vanderburgh
JSCR 2008)
Conclusions
Current physical fitness tests of the Army, Navy, and Air
Force:
– Are not potent determinants of physical military task performance
– Impose a physiological bias against heavier service members
Eliminating body mass bias may be more occupationally
relevant – must be tested empirically
Solutions
– Scaled values require no change to fitness test protocol but
create strange currency
– Correction factors provide ease of calculation, preservation of
original units, and require no equipment
– Balanced fitness tests require equipment but no calculations –
need validation
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