T. KITABAYASHI ET AL.
ESs between the mean of the obese group and the thin and
normal groups were 1.24 and 1.14 for grip strength, 1.76 and
1.66 for the 20-m shuttle run, and 1.03 and .67 for the standing
broad jump, respectively, and ES between the mean of the thin
group and obesity group was .79 for the 50-m run; the total
score was .61.
Discussion
The MEXT physical fitness test classifies the physical fitness
of young people into five grades based on the total score. The
subjects in the present study were all judged to have poor
physical fitness, corresponding to the D or E level, which is
lower than the standard level (C) among the five grades. Hence,
their physical fitness was considered to be inferior to that of
young people of the same generation.
The degree of obesity is generally determined by %BF. BMI
calculated from the height and weight has also been used
worldwide as a simple index of the degree of obesity in young
people. However, BMI has a limitation when used for subjects
with large muscle mass, such as athletes because of an
over-evaluating effect (Demura, 2011). However, it may be a
useful parameter to evaluate body composition in subjects other
than athletes because a strong relationship exists between the
two parameters (r = .86); thus, the grouping based on %BF
were judged to be valid.
Handgrip strength is used as an index of muscle strength be-
cause the results can be generalized to the whole body (Demura,
2011; The Ministry of Education, Culture, Sports, Science and
Technology, 2000). Grip strength was significantly greater in
the obese group (42 kg) than in the normal and thin groups,
with a large difference (ES = 1.14 - 1.24), and was comparable
to that of the Technical college students (grade 1, 41.5 kg;
grade 2, 43.6 kg; grade 3, 44.1 kg) who engage in high fre-
quency physical exercise (3 - 4 times/week) (Shima da, Demura ,
& Yamada, 2010). On the other hand, grip strength of the thin
group (34.8 kg) and the normal group (35.7 kg) was lower than
that of the obese group by 7 - 8 kg on an average. Grip strength
in the thin and normal groups was lower than the standard value
of the same generation. Hence, inferior muscle strength may be
a main factor of inferior physical fitness in the thin and normal
groups.
In particular, thin individuals tended to enforce weight loss
and dietary limitations more than that required because of an
excessive desire for a slim body (Hayano, 2002). As a result, a
risk of reduction in the amount of BF as well as muscle mass
has been indicated.
The 20-m shuttle run has been used as an index of general
endurance because of its strong correlation with VO2 max It
was significantly inferior in the obese group than in the thin and
normal groups (46.5 times), showing a very large difference
(ES = 1.66 - 1.76). In contrast to muscle strength, general en-
durance in the obese group was particularly inferior compared
with that in young people with poor physical fitness. In case of
the 20-m shuttle run, heavy weight because of large body
movements was considered to greatly affect performance and
impose a large burden on the knee joints of obese subjects. A
similar tendency was found in the 50-m run and standing broad
jump that require rapid body movements, wherein the obese
group was found to be inferior to the other groups.
The weight of obese subjects affects the motor ability tests,
which involve large body movements such as running and
jumping. Thus, it is necessary for obese subjects to reduce BF
mass while maintaining muscle mass to improve these physical
fitness elements related to running and jumping. No significant
difference was observed for tests such as sit-ups (general en-
durance), sit and reach (flexibility), side-stepping (agility), and
the handball throw (muscle power; throwing ability). These
tests do not require much body movement and are completed
within a relatively short time. Therefore, there was little effect
of body weight on performance. However, the mean values for
each group on these tests were equal to or less than the standard
value. This may be the main cause of poor physical fitness
among our subjects, which is common in all subjects with poor
physical fitness.
In particular, scores of the handball throw test were lower
than those of the other tests (approximately 18 m: 3 points).
The throwing movement is complex and requires energy gener-
ated by lower limbs to be amplified and transmitted smoothly
from the trunk to the upper limbs. It also requires whole-body
coordination in addition to muscle strength.
The following may be offered as the standard exercise pre-
scription to improve physical fitness of young males with poor
physical fitness. Strength improvement training is recom-
mended for thin or normal people with poor physical fitness
because they generally tend to have inferior muscular function.
On the other hand, obese people need to improve endurance
power through running/jumping exercises. These exercises may
be combined with strength training to increase basal metabo-
lism and aerobic exercise to reduce BF, considering the burden
on blood pressure and the joints. Furthermore, it may be desir-
able to include ball games promoting nerve functions into an
exercise program because all young people with poor physical
fitness perform inadequate exercise.
Conclusion
In conclusion, the cause of poor physical fitness was differ-
ent between the obese and thin groups among young people
with poor physical fitness. The obese group was superior in
muscle strength but inferior in general endurance and power
related to running and jumping, whereas the thin group was
inferior in muscle strength. Other physical fitness elements
showed little group differences.
Among young males with poor physical fitness, obese indi-
viduals have different physical fitness characteristics from
normal and thin individuals and are inferior to normal and thin
individuals in power and endurance of the whole body related
to running and jumping but superior in muscle strength.
Acknowledgements
This work was supported by Fukui National College Tech-
nology. The authors thank Prof. Shigeru Shimada and Dr. Ta-
kayoshi Yamada for their assistance with data collection. The
authors also thank Enago (www.enago.jp) for the English lan-
guage review.
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