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Metabolic Rate & the Evaluation of
Physical Performance in Children
HEAT BALANCE &
TEMPERATURE REGULATION
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METABOLISM:
CHEMICAL REACTIONS: HEAT & ENERGY
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HEAT LOSS:
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RADIATION, CONDUCTION, CONV ECT ION
EVAPORATION (skin & lungs)
WARMING INSPIRED Al R
URINE & FAECES
CONTROL:
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H Y P OT H A LAM U S
PERIPHERAL RECEPTORS
Comparison of core and peripheral temperatures
70%
27%
2%
1%
CONTROL IN NEWBORNS
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Mechanisms of shivering & sweating are poorly developed
Sweat glands immature
Large S.A./ Wt ratio
Thin subcutaneous adipose tissue layer
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LEADS TO INSTABILITY OF BODY TEMPERATURE
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Average body temperature drops with age
SD also drops, indicating better control
CONTROL IN NEWBORNS
 Vasoconstriction
well developed
 Crying increases metabolic rate
 Restlessness & increased
movements
 Brown fat
Vulnerability of the Adolescent Athlete
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There have been several deaths of
adolescent athletes
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Intense prolonged activity
High ambient temperature & humidity
Athletic equipment
Big (small S.A. /Weight ratio)
Lack of water
HEAT STROKE
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Sweating (Sweat is hypotonic)
Water leaves cells to hypertonic exterior
Water leaves blood, decrease in blood volume
High concentration of electrolytes in blood
Excessive water loss, sweating is shut-off
Temperature rises rapidly (>40ºC)
Heart failure
Metabolic Rate
Chemical reactions of the body
– Reactions = Energy + Heat
 Direct Calorimetry
– sealed chamber where all inputs
and outputs are monitored
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Indirect Calorimetry
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Determination of oxygen uptake
Spirometer for oxygen uptake
– OK for low levels of oxygen uptake
Collection and analysis of expired gases
Used as indicator of aerobic fitness
Respiratory Quotient
VCO2 produced
R
VO2 consumed
Respiratory Quotient (R.Q.)
 Carbohydrate
C6H12O6
+ 6O2 --> 6CO2 + 6H2O
R = 6CO2 / 6O2 = 1.0
 Fat
C16H32O2
+ 23O2 --> 16CO2 + 16H2O
R = 16CO2 / 23O2 = 0.70
Maximum Oxygen Uptake
VO2max testing
Treadmill
 Cycle ergometer (15% less)
 Criteria of max.
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Heart rate above 190
Subjects report
VO2 plateaus
Blood Lactate
R greater than 1.1
Reliability of VO2max (ml.kg-1.min-1)
in Children and Adolescents
Source
Boileau et al. (1977)
Cunningham et al. (1977)
Cureton (1976)
Paterson et al. (1981)
Sample
Test Type
Reliability
Coefficient
21 M, 11-14 y
Walk
r = .87
66 M, 10 y
Walk/Run
r = .56
27 M & F, 7-12 y
Walk
r = .88
8 M, 10-12 y
Walk
Jog
Run
R = .47
R = .87
R = .95
Note. r = interclass reliability; R = intraclass reliability
(Fitnessgram Reference Guide)
Typical R values for Height (0.99) and Skinfold (0.96) measurements