Tel Aviv University Fleishman Faculty of Engineering Dept

Tel Aviv University Fleishman Faculty of Engineering Dept. of Biomedical Enginering Biomedical applications of a Contact Resistance Variation p-mat Roberto Steindler Università degli Studi di Roma “La Sapienza” Dipartimento di Meccanica e Aeronautica

DMA pressure map sensor: applications Static and dynamic fatiguing exercises: postural stability increases, particularly in one leg stance posture – the p-mat can be used to quantify the increases Functional Reach test - the p-mat can be used to control the test is made correctly Human hopping and lower limb diagnostic - the p-mat can be used to analyse hopping characteristics Normal sitting involves displacements and changes in p -distribution - the p-mat can be used to acquire the changes in view of decubitus ulcer prevention

The p-mat sensor kapton Conductive strips velostat Sensor of 32 x 64=2048 sensing elements Dimentions: 16 x 32 cm 2 kapton Lateral view Contact resistences velostat row column kapton

The new p-mat sensor

The p-mat sensor Thickness: 150 mm Range: 400 – 500 k. Pa Sensitivity threshold: 15 – 20 k. Pa No hysteresis No response delay Some drift

Human posture is a dynamic fact Human posture is characterized by body sway Body sway increases with fatigue One leg posture underlines the body sway Postural stability (or instability) can be shown by a pmat acquisitions

Plantar pressure map acquisition during one leg posture

How postural stability can be quantified? COP coordinates are calculated for each acquisition (30 s) XCOP (t) and YCOP (t) are plotted and RMS(x) and RMS(y) are calculated FFT come from time trends and maximum significative frequencies are shown COP trajectory (stabilogram) is plotted and its length and area are calculated All these parameters can be assumed as postural stability indexes: the greatest the index is

Fatigue effect on postural stability p maps are acquired (three 30 s acquisitions or longer time acquisitions) Fatiguing exercise p map acquisitions Postural stability indexes are calculated before and after the fatiguing exercise Index variations for single subjects and for a whole population are calculated Statistic tests are applied to index variations

XCOP and YCOP - time trend Amplitude (distance rows/columns: 0. 5 cm) YCOP XCOP RMS XCOP 0. 21 cm 20 frames=1 s XCOP and YCOP displacements vs time and the corresponding RMS values before a fatiguing exercise Amplitude (distance rows/columns: 0. 5 cm) RMS YCOP 0. 30 cm YCOP XCOP RMS YCOP 0. 61 cm RMS XCOP 0. 28 cm 20 frames=1 s XCOP and YCOP displacements vs time and the corresponding RMS values after the fatiguing exercise

XCOP Frequency amplitude [mm/Hz] XCOP and YCOP - frequency spectrums Frequency [Hz] YCOP Frequency [Hz] XCOP Frequency [Hz] Frequency amplitude [mm/Hz] frequency spectrum of the XCOP and YCOP signals before a fatiguing exercise YCOP Frequency [Hz] frequency spectrum of the XCOP and YCOP signals after the fatiguing exercise

Scarto quadratico medio di Xb e Yb: Analisi in frequenza: Massima ampiezza Frequenza in corrispondenza alla massima ampiezza Massima frequenza significativa

Columns The stabilogram characteristics Rows Length: 53. 5 cm Length: 80. 6 cm Area: 1. 01 cm 2 Area: 2. 16 cm 2 Stabilogram before a fatiguing exercise Rows Stabilogram after the fatiguing exercise

Static fatiguing protocols 30 s single stance posture (acquisition) ü Weight on dominant leg 4 min of fatiguing exercise 30 s single stance posture (acquisition) 5 min single stance posture (acquisition) üKeeping Crouching Fatiguing exercise: as long as possible 5 min single stance posture (acquisition)

Dynamic fatiguing protocols üCycling on a cyclette at 20 km/h an increasing inclinations 3 min and 30 s single stance posture (acquisition) Fatiguing exercise : 4 min and 30 s 3 min and 30 s single stance posture (acquisition) üAerobic run on a treadmill Fatiguing exercise: 12 min 3 min and 30 s single stance posture (acquisition)

Weight on dominant leg 30 s with dominant leg on p-mat, contralateral knee flexed at 90°, hands resting on waist 4 min sitting in upright position , 10 kg dead weight hanged up with a strap on the dorsal aspect of the dominant foot 30 s with dominant leg on p-mat, contralateral knee flexed at 90°, hands resting on waist Each subject repeats the protocol three times in three different days

Weight on dominant leg 10 young healthy subjects (9 males, 1 female) Age 26. 5 1 years All the subjects have given their approval The results of each subject come from the means of the three acquisitions

Weight on dominant leg increase 36% 21% 38% 31% 32% 54% The whole population mean values, the standard deviations and the percentage increases of the postural stability indexes from non fatigued to fatigued condition standing on the dominant leg

Weight on dominant leg

Crouching fatiguing protocol 5 min with dominant leg on pmat, contralateral knee flexed at 90°, hands resting on waist Keeping crouching with knee flexed at 90° as long as possible 5 min with dominant leg on pmat, contralateral knee flexed at 90°, hands resting on waist

Crouching fatiguing protocol 11 young healthy subjects (7 males, 4 females) Age 25. 2 1. 3 years All the subjects have given their approval The results of each subject come from the means of the 30 s ten periods

Crouching fatiguing protocol - The whole population mean values, the standard deviations and the percentage increases of the postural stability indexes from non fatigued to fatigued condition standing on the dominant leg

Crouching fatiguing protocol

Cyclette fatiguing protocol 3 min and 30 s with dominant leg on p-mat, contralateral knee flexed at 90°, hands resting on waist 4 min and 30 s cycling at 20 km/h at the growing inclinations 3 min and 30 s with dominant leg on p-mat, contralateral knee flexed at 90°, hands resting on waist

Cyclette fatiguing protocol 10 young healthy subjects (5 males, 5 females) Age: 25, 5 + 1, 5 years All the subjects have given their approval The results of each subject come from the means of the 30 s seven periods

Cyclette fatiguing protocol The whole population mean values, the standard deviations and the percentage increases of the postural stability indexes from non fatigued to fatigued condition standing on the dominant leg

Cyclette fatiguing protocol

Treadmill fatiguing protocol 3 min and 30 s with dominant leg on p-mat, contralateral knee flexed at 90°, hands resting on waist 12 min running at the anaerobic speed 3 min and 30 s with dominant leg on p-mat, contralateral knee flexed at 90°, hands resting on waist

Treadmill fatiguing protocol 10 subjects (9 males, 1 female) Age 25. 9 3. 5 All the subjects have given their approval The results of each subject come from the means of the 30 s seven periods

Treadmill fatiguing protocol

Treadmill fatiguing protocol

Functional Reach Test • Functional Reach: is the maximal distance one can reach forward beyond prevalent arm lenght, while mantaining a fixed base of support in a a standing position • Test start: right angle with the trunk • Correct test: the clenched fist must be mantained at the same height; the heel must not rise

• Functional Reach: a test run varing normal posture • A test which can put in evidence muscolar-skeletal or neurological problems • These problems change the ability in mantaining equilibrium • The movement during the test is natural and istinctive

Facilities • A tape is used to misure the Functional Reach • The p-mat is used to control the test (the heels do not rise) • From the p-map acquisitions the Co. P trajectory and its components can be plotted

Parameters acquired during Functional Reach test 1) Functional Reach displacement - FR[cm] 2) Co. P displacement in test direction - DCo. P [cm] 3) Test lenght – time [s]

Plantar pressure acquisition with p-mat

X-Co. P(t) and Y-Co. P(t) • • Test lenght: 15 s Subjects stands upright 5 s Functional Reach movement Waiting upright stabilogram

Functional Reach test - execution • Tested populations 20 young healthy subject ; 10 males and 10 females; medium age: 22, 3 ± 2, 1 years 14 elder healthy subjects ; 11 males and 3 females; medium age 61, 5 ± 3, 8 years • All the subjects are healthy (no orthopedic or neurological problems) and they can mantein upright position at least 10 minutes • All subjects have given their approval • Each subject runs three tests at natural speed and three tests at maximum speed allowed by his status • The resuslts of each subject (Functional Reach and DCo. P in the two conditions), come from the means of three acquisitions

Young subjects Population’s Results Elder subjects

Result comparison Comparison between young and elder subjects

About results FR young: normal speed 35, 6 ± 3, 5 cm; max speed 35, 0 ± 3, 5 cm Co. P young: normal speed 7, 0 ± 1, 7 cm; max speed 7, 4 ± 1, 5 cm FR elder: normal speed 31, 0 ± 4, 3 cm; max speed 28, 9 ± 2, 6 cm Co. P elder: normal speed 5, 1 ± 1, 5 cm; max speed 5, 1 ± 1, 1 cm • Functional Reach decreases for both population from normal to maximum speed; the decrease, significative 95% only for elder population, comes from requirement of going back as soon as possible to the upright position • Co. P movement shows a light increase from normal to maximum speed; the increase means a grater effort in mantaining equilibrium • Functional Reach decreases from young to elder population both at normal and maximum speed; the decrease significance is 99% • Also Co. P movements decreases from young to elder population both at normal and maximum speed; also in this case the decrease significance is 99%

About Functional Reach • Functional reach is a real clinical test to compare different age population • The comparison shows a significant decrease of FR and DCo. P with age • Functional Reach measure may identify damages that cause balance instability • Functional Reach test can be extended to not completely selfsufficient subjects (ictus, Parkinson, Alzheimer, orthopedic traumas)

Human hopping Characteristics and purposes of human hopping test Human hopping analysis is useful for limb diagnostic Normal hopping and abnormal hopping can be compared By the p-mat it is possible to measure flight lenght; it is also possible to study the “take-off” and the “landing” characteristics

Hopping test description 30 seconds hopping from 6 healthy subjects 3 test from each subject after their approval Hopping phases Take-off Flight lenght Landing

Plantar pressure acquisitions One leg hopping Two legs hopping

About hopping Preliminar results During take-off and landing anterior foot is more loaded During landing weight increases are about 15% Time flight decreases from test n° 1 to test n° 3 flight lenght and flight height decrease as the subjects is getting fatigued The test is a not invasive test and can be applied to sporting people

Decubitus ulcer prevention • • • To be developed common program Roma – Tel Aviv Acquiring p-maps during healthy subjects sitting Characterization of buttom displacements Imposing the dispalcements to invalid subjects Decubitus ulcer prevention

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