Page 40 - JSOM Summer 2022

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some performance dietitians in the SOF Human Performance z-score 3.9 ± 0.8). A z-score is calculated from the phantom
Programs are utilizing the International Society for Advanced reference for each of the five-way fractionation compartments
Kinanthropometry (ISAK) profile to assess body composition, as well as each individual length, breadth, skinfold, and girth
proportionality, ratio of muscle to bone, and somatotype in measured in the full ISAK profile. For tracking individuals
combat Operators. Kinanthropometry is defined as the study longitudinally, girth circumferences and skinfold thickness are
of human size, shape, proportion, composition, maturation, modifiable variables. They can also be used to track progress
and gross function and it is a helpful tool for monitoring nutri- in coordination with specific nutrition and strength routines,
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tion and training progress in athletes and active individuals. or to monitor recovery from injury, as these measurements will
Unlike a two-compartment model that divides the body into show small changes in muscle and fat over time. While mus-
fat and fat-free masses, the ISAK profile is based on a five-way cle and fat are modifiable with diet and exercise, bone size
fractionation method to determine body mass contribution and structure are fairly stabilized by adulthood. From muscle
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from skin, adipose tissue, bone, muscle, and residual mass. and bone fractionation compartments, an individual’s muscle:-
Results from cadaver dissection studies have shown errors in bone ratio can be calculated (muscle mass kg/bone mass kg),
assuming density of fat and fat-free mass, with better predic- and this is important to track not only homogeneity in sport
tive accuracy when adipose tissue is estimated separately from but also injury risk. For example, muscle:bone ratio in profes-
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essential fat. Even dual-energy x-ray absorptiometry (DXA) sional team sports (male rugby and soccer players) ranges be-
uses a three-compartment model to estimate fat-free mass, bone tween 4 and 5, compared to tournament winning powerlifters
mineral mass, and fat mass but does not estimate muscle mass. whose mean ratio was 5.3 ± 1.0. 14,15,18 A high muscle:bone ra-
tio indicates either extreme musculature development or small
By contrast, the ISAK profile consists of 42 noninvasive an- skeleton, both of which may stress bones and increase the
thropometric measurements of skinfold thicknesses, muscle likelihood of musculoskeletal and/or bone injury. Thus, this
girths, bone lengths, and bone breadths to estimate each of ratio may be used to determine the optimal muscle mass an
the five-way fractionation compartments (skin, adipose tissue, Operator can carry for his frame size. Furthermore, through
bone, muscle, and residual mass). Adipose tissue calculated setting appropriate muscle:bone ratio and sum of six skinfold
in this model includes fat in subcutaneous tissue, surrounding goals, an ideal body weight for optimal performance can be
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organs, viscera, and intramuscular tissue. This estimate of calculated. Muscle:bone ratio and body fat can also be used
total adipose tissue differs from the chemical body fat percent- in conjunction with somatotype, a measure of body shape
age calculated from body density using Archimedes principle, and form calculated using the Heath-Carter Method. Scores
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which assumes fat/lipids have a constant density of 0.9g/cm . are calculated for each of the three somatotypes: mesomorph
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The ISAK protocol does provide an estimate of conventional (high musculature), ectomorph (lean), and endomorph (high
body fat percentage, but body fat is not the primary outcome body fat). Somatotypes for the samples of male soccer and
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nor is the calculation dependent on a regression equation. rugby players trend predominantly mesomorphic. 14,15 While
In addition to body fat, many publications report the sum of individual measurements and deviation from the phantom
skinfolds (sum of six includes triceps, subscapular, supraspi- mean provide helpful anatomical data, somatotype provides
nale, abdominal, front thigh, and medial calf) as an indication an overall picture of the Operator body type.
of subcutaneous fat. 14–17 Compared to body fat percentage es-
timated from equations, a sum of skinfolds provides a direct The ISAK profile has been well established as international
and more sensitive marker of total body and regional body fat method for talent identification, distinguishing characteristics
changes without mathematical manipulation. Furthermore, between athletes across and within elite sports, and identify-
the ISAK protocol has a standard technical error of measure ing predictors of sport performance that can be applied in the
(TEM) for Level 2 anthropometrists of maximum of 5% for military setting. For example, rock climbers were shorter
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skinfolds and 1% for all other measures. Although ISAK has a in standing height but had a higher arm:leg ratio and greater
standard reference maximum for error, the TEM can be calcu- arm length:body height ratio compared to untrained individu-
lated specifically for the anthropometrist. It also provides the als. These data show that the best rock climbers had longer
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practitioner with a capability to objectively discern between than average arms on a shorter than average body or, in other
significant changes versus trends and/or no changes between words, a high ape index indicative of greater wingspan:height
sum of six skinfold measurements in order to make appro- ratio. In addition to genetic traits, the ISAK profile shows
priate nutrition and training adjustments for the Soldier. Sum modifiable characteristics linked to improved performance.
of six skinfolds reported in the elite male athletic population Greater muscle:bone ratios have been demonstrated in power
(soccer and rugby) range from 48 to 114 mm. 14,15 These sports lifters who won their events compared to their competitors. 18
better compare to SOF Operators than endurance athletes. The strongest power lifters had greater muscle mass (as evi-
denced by greater circumference in flexed upper arm and chest
From measured anthropometric data, body proportionality girth) compared to weaker competitors despite no significant
is compared to the phantom reference, a unisex metaphorical differences in bone breadth or length. Most ISAK data have
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model created from existing pooled data of many population been published on international Olympic sport athletes, leav-
groups. The phantom reference height is 170 ± 6 cm with ing a gap in the literature for military application. Neverthe-
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mass 65 ± 9 kg. An important disclaimer is that the phan- less, many performance dietitians in the SOF community have
tom reference represents neither a real nor ideal human size. been certified in ISAK testing. Furthermore, unlike InBody,
Rather, it is a tool for comparison between individuals with Bod Pod, or DEXA, the ISAK method uses portable equipment
calculation of a statistical z-score or variation from the mean, that allows a dietitian to measure the Operator in a field envi-
assuming that anthropometric characteristics are normally dis- ronment. While SOF dietitians are utilizing the ISAK profile,
tributed. For example, professional rugby players carry muscle the challenge lies in translating sport data to military relevant
mass 2–4 standard deviations above the phantom reference, outcomes. According to Daigle et al. (2015), “It is import-
highest in those playing positions in the front row (muscle ant to remember that in human performance optimization, a

38 | JSOM Volume 22, Edition 2 / Summer 2022