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Ground reaction force analysis of a variety of jumping activities in growing children Tsang, Garry
Abstract
In recent years, the role of physical activity for the development and maintenance of a healthy skeleton and for the prevention of osteoporosis has garnered significant research interest. These studies have revealed that high impact loads with an unusual strain distribution are generally thought to be more effective in eliciting an osteogenic response than low impact repetitive activities. Also, immature bones appear to have a greater capacity to adapt to mechanical loads than mature bone. Childhood intervention programs that utilized different weight bearing activities and games including jumping have demonstrated a positive bone response to mechanical loading (McKay et al., 2000, Bradney et al., 1998, Morris et al., 1997, Heinonen et al., in press). However, the biomechanical characteristics of effective interventions have never been described. We addressed the question "what ground reaction forces (GRFs) are associated with pediatric mechanical loading intervention programs?" To accomplish this we measured the maximum GRF, rates of force, impulses and time to maximum force for twelve different jumping activities on a Kistler 9251A force platform (Winterthur, Switzerland). Jumps measured included drop jumps from 10, 30 and 50 cm, followed by a plyometric jump, submaximal and maximal jumping jacks, alternating feet, counter movement jumps and side to side jumps over 10 and 20 cm foam barriers. We also examined the relationship between bone mineral density (BMD) at the proximal femur, physical activity (PA) and dynamic power. The subjects were 70 children (36 boys and 34 girls), 8.3-11.7 years old. Height (cm) and mass (kg) were measured using standard techniques. BMD (g/cm²) at the hip and lean and fat mass (g) from the total body scan were assessed by dual energy X-ray absorptiometry (DXA, Hologic Inc). PA was assessed by questionnaire and a composite loading activity score was derived for each subject. Dynamic power was assessed with a vertical and standing long jump using standard procedures. Subjects ranged in height from 128.4 - 172.6 cm and with mass of 25.0 - 57.0 kg, on average. Mean (SD) for vertical jump was 24.2 (5.5) cm and 135.2 (16.6) cm for standing long jump. The children engaged in loaded PA an average of 5.7 (5.2) hours per week. BMD (g/cm²) for total proximal femur, femoral neck and trochanter was 0.70 (0.09), 0.67 (0.08) and 0.58 (0.08), respectively The highest mean maximum GRFs, normalized for body weight (BW), were generated from the plyometric portion of the drop jumps and the counter movement jump (on average 5 BW) compared to 3.5 BW for jumping jacks. Similarly, highest fates of force were 514 BW/sec for the plyometric jump from 10 cm and 493 BW/sec for the counter movement jump. In hierarchical regression, lean mass (β = 0.56) and long jump distance (β = 0.33) were significant predictors of femoral neck BMD accounting for 42% of the total variance. Our findings demonstrated that relatively high and diverse GRFs and rates of force are generated by jumps included in a pediatric exercise intervention trial. As forces at the hip are known to be approximately 3 times the measured GRF (Bassey et al., 1997), the GRFs measured in the present study would be associated with forces 15 BW at the proximal femur. These findings could be used to modify ongoing interventions or to develop new targeted interventions for bone health in children.
Item Metadata
Title |
Ground reaction force analysis of a variety of jumping activities in growing children
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
2000
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Description |
In recent years, the role of physical activity for the development and maintenance of a
healthy skeleton and for the prevention of osteoporosis has garnered significant research
interest. These studies have revealed that high impact loads with an unusual strain
distribution are generally thought to be more effective in eliciting an osteogenic response
than low impact repetitive activities. Also, immature bones appear to have a greater
capacity to adapt to mechanical loads than mature bone.
Childhood intervention programs that utilized different weight bearing activities and
games including jumping have demonstrated a positive bone response to mechanical
loading (McKay et al., 2000, Bradney et al., 1998, Morris et al., 1997, Heinonen et al., in
press). However, the biomechanical characteristics of effective interventions have never
been described.
We addressed the question "what ground reaction forces (GRFs) are associated with
pediatric mechanical loading intervention programs?" To accomplish this we measured
the maximum GRF, rates of force, impulses and time to maximum force for twelve
different jumping activities on a Kistler 9251A force platform (Winterthur, Switzerland).
Jumps measured included drop jumps from 10, 30 and 50 cm, followed by a plyometric
jump, submaximal and maximal jumping jacks, alternating feet, counter movement jumps
and side to side jumps over 10 and 20 cm foam barriers. We also examined the
relationship between bone mineral density (BMD) at the proximal femur, physical
activity (PA) and dynamic power.
The subjects were 70 children (36 boys and 34 girls), 8.3-11.7 years old. Height (cm)
and mass (kg) were measured using standard techniques. BMD (g/cm²) at the hip and
lean and fat mass (g) from the total body scan were assessed by dual energy X-ray
absorptiometry (DXA, Hologic Inc). PA was assessed by questionnaire and a composite
loading activity score was derived for each subject. Dynamic power was assessed with a
vertical and standing long jump using standard procedures.
Subjects ranged in height from 128.4 - 172.6 cm and with mass of 25.0 - 57.0 kg, on
average. Mean (SD) for vertical jump was 24.2 (5.5) cm and 135.2 (16.6) cm for
standing long jump. The children engaged in loaded PA an average of 5.7 (5.2) hours per
week. BMD (g/cm²) for total proximal femur, femoral neck and trochanter was 0.70
(0.09), 0.67 (0.08) and 0.58 (0.08), respectively
The highest mean maximum GRFs, normalized for body weight (BW), were generated
from the plyometric portion of the drop jumps and the counter movement jump (on
average 5 BW) compared to 3.5 BW for jumping jacks. Similarly, highest fates of force
were 514 BW/sec for the plyometric jump from 10 cm and 493 BW/sec for the counter
movement jump. In hierarchical regression, lean mass (β = 0.56) and long jump distance
(β = 0.33) were significant predictors of femoral neck BMD accounting for 42% of the
total variance. Our findings demonstrated that relatively high and diverse GRFs and rates
of force are generated by jumps included in a pediatric exercise intervention trial. As
forces at the hip are known to be approximately 3 times the measured GRF (Bassey et al.,
1997), the GRFs measured in the present study would be associated with forces 15 BW at
the proximal femur. These findings could be used to modify ongoing interventions or to
develop new targeted interventions for bone health in children.
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Extent |
7936462 bytes
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Genre | |
Type | |
File Format |
application/pdf
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Language |
eng
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Date Available |
2009-07-20
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Provider |
Vancouver : University of British Columbia Library
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Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
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DOI |
10.14288/1.0077253
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
2000-11
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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Item Media
Item Citations and Data
Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.