Bioengineering - Human Movement

What is the requirement of human movement

neurological control of muscle activation

Cause and treatment of arthritis

• Caused by thinning or damage to the cartilage

• treatment such as knee braces, footwear to reduce mechanical loading

Consequence of diabetes

Reduced healing ability causes diabetic foot ulceration leading to amputation or death. New footwear designed to reduce mechanical loading.

Human movement measurement methods

• Video Cameras

• Infrared Motion Tracking Cameras

• Internal Sensors such as accelerometers and gyroscopes

Human Movement Measurement Methods Comparison

Video Motion Tracking Process

• Manual Analysis - approximate body segment angles taken from video footage

• Software Analysis - data collected and mapped to a computer model to calculate body loading

• Automated real-time motion tracking - mathematical model mapped to video image to approximate joint angles

Gait Laboratory Motion Analysis Process

• Infrared sensors used with emitters and detectors to create a capture volume with 8-10 cameras

• Force Plates then used - Key measures of ground reaction force in vertical, anterior-posterior and medial-lateral directions

• A body segment model is then made with local coordinate frames. Inverse dynamics, anthropometrics and GRF combine together

Inertial Movement Units

• Mass puts strain on a sensor

• Uses accelerometers, gyroscopes and magnetometers

• Software fuses data from multiple sensors

• Absolute orientation is determined

Wearable IMUs design considerations

• Sensor placement - number of sensors, user acceptance (what people are willing to wear or do)

• Calibration - considering differing local coordinate frames, standard vs. real time movement

• AI and cloud computing - consider issues around sharing and storing data and large amounts of training data

3 layers of skin

• epidermis: protective barrier against environments and regulates water loss

• dermis: contains papillary and reticular layers that has blood vessels, nerve endings and dense connective tissue. Provides strength and elasticity

• hypodermis: deepest layer containing fat cells and connective tissue. acts as an insulator and provides shock absorption

Skin Function

• physical protection

• Water and electrolyte balance

• temperature regulation

• Vitamin D synthesis

• Immune Function

• Sensation

• Energy Storage

Cell actions in skin healing

1) Inflammatory Phase: platelets form clots, neutrophilis clear debris, macrophages remove dead skin cells

2) Proliferative Phase: Keratinocytes re-epithelialize, fibroblasts produce collagen, endothelial cells form new capillaries

3) remodelling phase: fibroblasts strengthen ECM, myofibroblasts contract wound edges, keratinocytes reinforce epidermal barrier.

Cycle of excessive skin loading

1) Primary, direct deformation damage

2) secondary inflammatory edema-related damage

3) Tertiary ischemic damage

People more susceptible to skin injuries

• Elderly with aged, underdeveloped tissue

• Medical conditions (diabetes)

• People on long term coagulant

Design requirements to prevent skin ulcerations from bed pressure

• Can adjust pressure distribution during surgery

• Will not change whole body position

• Can meet safety regulations for medical devices ISO13485

• Can be integrated with current surgical table

Prevention and treatment of a diabetic foot ulcer

• to prevent: shock absorbing insoles and foot sensors to sense hot spots or areas of high pressure

How does muscle contraction and activation happen?

structure of a muscle fibre

Made up of many myofibrils bundled together. They can split into a number or contractile elements, sarcomeres

Muscle Contraction

• Muscles move on commands from the brain

• motor neurons fires action potentials down the axon

• A chemical is released at the ending

• Change in electric field causes contraction in the muscle

Conditions that affect neuromuscular control

• Parkinson’s

• Post-stroke disability

• Multiple Sclerosis

• Muscular Dystrophy

Methods to understand muscle activation

• Physiological cross-sectional area and muscle structure

• Electromyography (EMG, or ECG for heart)

• Mathematical modelling

Measuring PCSA

• Measure the pennation angle:

  PCSA = M cos(theta) / rho*l

Purpose of electromyography

It measures the electrical activity produced from muscle activation. Can be done using surface electrode measurement or intermuscular electrode measurement.

Set up for EMG

one signal electrode, one ground electrode. Signals then amplified using an amplifier. Data acquisition device used.

What are the considerations for good EMG measurement?

• Skin cleaning/Abrasion

• Electrode placement

• Electrode design

• Signal cable length/amplification

• Post-Processing

What is functional electrical stimulation and how does it work?

electrical stimulation can be used in wound and tissue healing. a stimulator, leads and electrodes are used to stimulate nerves by applying an electrical potential between the electrodes, creating local depolarisation, resulting in action potential. It is both and assistive and rehabilitative technology