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Eric's PhD project
Transcript of Eric's PhD project
Effects of weight loss
Effects of muscle strength
Modelling and simulation
SUS international open fund
Dr Yanxin Zhang
Dr Sharon Walt
Prof. Elwyn Firth
Prof. Peijie Chen
Dr Jie Zhuang
Dr Sarah Shultz
Prof. Weimo Zhu
Department of Sport and Exercise Science, UoA
Shanghai University of Sport
Peak Weight Management Ltd
Inefficient body mechanics
What is the cause-and-effect relationship between excess body mass, gait biomechanics and energetics?
How muscle strength contributes to gait profile in obese individuals?
The flow diagram of the process of biomechanical and energetic data.
Weight loss intervention
Diet and exercise-induced weight loss
Two hour aerobic exercise per session
Two session per day
Six days exercise a week
Effectiveness of intervention
Increased absolute and relative isokinetic strength.
Walking speed increased 0.06m/s
Greater hip flexion moment, mechanical work
Increased metabolic rate and MEE (both absolute and normalized)
3D gait analysis and oxygen uptake
0.15 m/s slower walking speed
10.0% less cadence
30.9% longer double support phase
Larger hip adduction/abduction ROM
Smaller knee flexor/extension, knee valgus/varus and ankle plantar/dorsiflexion ROM
Greater absolute moments at all joints.
Greater normalized hip internal rotation moment, abduction moment and flexion moment.
Smaller normalized ankle plantarflexion
72.7% higher mechanical energy expenditure
65.7% higher metabolic energy expenditure
Similar mechanical efficiency
Greater absolute ankle flexor & extersor strength
Smaller knee and ankle normalized flexor & extersor isokinetic strength
Low caloric diet
No change in spatiotempral parameters.
Most of joint moments decreased in proportion to weight loss.
Hip kinematics and kinetic signified a key gait adaptation to weight loss.
Reduced hip adduction/abduction ROM
Reduced hip flexion moment
Reduced hip power absorption
Significantly reduced the metabolic and mechanical energy cost , while maintained the mechanical efficiency.
8 boys, 10 girls
9 boys, 10 girls
8 girls, 11 boys
8 girls, 10 boys
Strength training using elastic band
Subject-specific computational modelling and simulation
Evaluation of simulated results
force and muscle forces
Muscle function analysis
Higher absolute compressive tibiofemoral force
Need more quadriceps forces rather than gastrocnemius force during push-up.
Using similar muscles groups to support and accelerate body COM, but significantly smaller contributions of individual muscles
Simulated muscle activation VS. EMG
Muscle contribution to COM
Demonstrated the impact of obesity on children's gait strategy at both joint and musculoskeletal level.
Identified three reasons for altering gait strategy:
to minimize energy expenditure and maintain mechanical efficiency
to avoid increasing knee joint load
to reduce muscle requirements or compensate potential muscle weakness (i.e ankle plantarflexor)
Applied musculoskeletal modelling and simulation method in obese individuals
What I have done
1. Self-selected speed walking should be recommended in the early stage of intervention
2. Monitoring and recording of the self-selected speed over time
3. Combine biomechanical analysis and simulations with physiological examination
4. Integration muscle strength training into
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Research Quarterly for Exercise and Sport
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, Zhang Y, Zhuang J. (2013) The application of computer modelling and simulation to investigate compressive tibiofemoral force and muscle functions in obese children,
Computational and Mathematical Methods in Medicine
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, Zhuang J, Zhang Y. (2013) A method of speed control during over-ground walking: using a digital light-emitting diode light strip.
Advanced Materials Research
, 718-720: 1371-1376
, Zhang Y, Zhuang J. (2012). The effect of weight loss on gait characteristics of obese children.
Obesity Research & Clinical Practice
, 6: 35
, Zhang Y, Zhuang J, Walt S. Short term diet and exercise induced weight loss reverses the effects of obesity on gait biomechanics and energetics in children. The 12th International Congress on Obesity, Kuala Lumpur, Malaysia, March 17-20, 2014
, Zhang Y, Zhuang J. Effects of lower extremity strength training on gait patterns in obese children, The 31th Conference of the International Society of Biomechanics in Sport, Taipei, Taiwan, July 7 - 11, 2013
, Zhuang J, Zhang Y. The effect of weight loss on gait characteristics of obese children. The Australian and New Zealand Obesity Society Annual Conference 2012, Auckland, New Zealand, October 18 - 19, 2012
, Zhang Y. The effect of body mass on the children’s biomechanics and energetic cost during walking, SESNZ Annual Conference 2011, Auckland, New Zealand, November 18 - 19, 2011.
Energy-saving gait mechanics
Similar COM displacement
Current knowledge about the cardiac rehabilitation and exercise prescription do
consider the biomechanical characteristics of persons with obesity.
Altered movement strategy
Biomechanics and energetics differences
--- to avoid the increase of metabolic cost and the mechanical work required to lift, lower, accelerate, and decelerate
Compensate potential muscle weakness
To decrease joint loading
Smaller relative muscle strength
Less hip extension - weak hip extensors
Reduced ankle plantarflexor moment
Similar knee joint moment
Simulated kinematics VS. experimental data
Focus on target muscles specific to the obese individual's needs
Perform a serial critical reviews of the intervention
Achieve a better balance between energy cost and musculoskeletal health