8 research outputs found
Characterisation of running specific prostheses and its effect on sprinting performance
Thesis (PhD)--Stellenbosch University, 2015.ENGLISH ABSTRACT: The development of the running specific prosthetic (RSP) has allowed athletes with lower limb amputations to
participate at a high level in sports such as sprinting. Literature regarding mechanical properties of RSPs and
their influence on the athleteâs performance, on the other hand, is limited. This makes prosthetic selection a
difficult task. The aim of this study was to assess the biomechanical and physiological effects of the mechanical
characteristics of different RSPs on an athleteâs sprinting performance.
The sprint performances of athletes with lower limb amputations were described in a retrospective analysis of
Olympic and Paralympic times between 1992 and 2012, in an attempt to assess whether the technological
advances in RSPs is evident. A 14 â 26% performance improvement was found for the T42 and T44 classes
of the 100 and 200 m during this time in comparison to 2.2 â 2.8% for the Olympic athlete performances. These
results were further supported by the lower competition density found in the amputee groups (Olympic 23.90
and 9.29 competitors.s-1; T42 4.53 and 1.93 competitors.s-1). It was therefore proposed that technology played
a significant role in the performance progression of these athletes over the last 20 years.
Differences in the characteristics of two RSP models (model E and X) were investigated. This was achieved
by athlete independent mechanical testing during which the RSPs were dropped from a height of 30 cm and
left to bounce on a force platform. The results revealed differences in the peak ground reaction force (GRFpeak)
(model E > model X; p model E; p < 0.05). This
indicated that the RSP model E is more stiffness than the model X.
These stiffness characteristics related to discrepancies in sprinting economy of an athlete completing four
maximal anaerobic running tests (MART) using different RSPs. Two RSP stiffness categories of each model
(Ecat4, Ecat6, Xcat4, Xcat6) were used for this testing and was randomly allocated to each testing session. It was
found that the running speed at which the athlete attained a blood lactate concentration of 10 mmol.l-1 was the
highest with the stiffest RSP (Ecat6), whereas it was the lowest in the softest RSP (Xcat4). Accordingly the lowest
functional muscular fatigue as measured by a decrease in the pre and post-test counter movement jump height
was found in this condition (Ecat6 7.35% vs. Xcat4 24.43%).
From these investigations it was clear that technology is an important factor in the performances of amputee
sprint athletes. Therefore prosthetic selection is of the utmost importance. Differences in the mechanical characteristics of the RSPs influence the sprint physiology and biomechanics and should therefore be taken
into consideration when selecting a RSP.AFRIKAANSE OPSOMMING: Die ontwikkeling van hardloop-spesifieke prostese (In Engels, running specific prosthetic, RSP) laat atlete met
onderste ledemaat amputasies toe om op ân hoĂ« vlak aan sportsoorte soos naellope deel te neem. Slegs
beperkte literatuur aangaande die meganiese eienskappe van RSPs en die invloed daarvan op prestasie is
beskikbaar. Die doel van die studie was om die effek van verskillende meganiese eienskappe op die
biomeganiese en fisiologiese prestasie van ân atleet te evalueer.
In ân retrospektiewe analise van die Olimpiese en Paralimpiese resultate in die 100 en 200 m tussen 1992 en
2012 is die invloed van tegnologiese vooruitgang op atlete met onderste ledemaat amputasies ondersoek. ân
Prestasie verbetering van tussen 14 en 26% vir die 100 en 200 m van T42 en T44 atlete is gevind. In
vergelyking hiermee het die Olimpiese prestasie met slegs 2.2 â 2.8% verbeter. Hierdie bevinding word verder
gestaaf deur die laer kompetisie digtheid in die geamputeerde groepe (Olimpies 23.90 en 9.29 deelnemers.s-
1; T42 4.53 en 1.93 deelnemers.s-1). Gevolglik kan dit afgelei word dat tegnologie ân betekenisvolle uitwerking
op die prestasie verbetering van hierdie atlete het.
Ondersoek is verder ingestel op die verskillende karaktereienskappe van twee RSP modelle (model E en X).
Dit was uitgevoer deur middel van atleet-onafhanklike meganiese toetse. Tydens hierdie toetsing is die RSP
van ân 30 cm hoogte laat val en toegelaat om vrylik op ân kragplatform te hop. Die resultate het getoon dat
verskille tussen die piek grond reaksiekrag (In Engels, peak ground reaction force, GRFpeak) (model E > model
X; p model E; p < 0.05). Hierdie resultate dui daarop
dat die RSP model E groter styfheid as model X gehad het.
Hierdie styfheid karaktereienskappe het verband gehou met die variasie in die naelloop ekonomie van ân atleet
wat vier maksimale anaërobiese hardlooptoetse (MART) met verskillende RSPs voltooi het. Vir die toetsing is
twee styfheid kategorieë RSPs van elke model gebruik (Ecat4, Ecat6, Xcat4, Xcat6). Hierdie RSPs is lukraak aan
die atleet vir elke toets toegeken. Die hardloopspoed waarteen die atleet ân bloedlaktaat konsentrasie van 10
mmol.l-1 bereik het, was die hoogste met die styfste RSP (Ecat6), teenoor die laagste spoed wat gevind is in die
mees buigbare RSP (Xcat4). Dienooreenkomstig was die laagste funksionele spiervermoeĂŻenis, soos gemeet
deur ân afname in die voor en na toets teenbeweging sprong (In Engels, counter movement jump, CMJ), ook
gevind met die gebruik van die styfste RSP (Ecat6 7.35% vs. Xcat4 24.43%). Dit was duidelik dat tegnologie ân belangrike rol speel in naellope vir atlete met amputasies. Hierdie resultate
toon die belangrikheid van prostese keuse. Verskille in die meganiese eienskappe van die RSPs beĂŻnvloed
beide die fisiologiese en biomeganiese response tydens die naelloop en moet gevolglik in ag geneem word
wanneer ân RSP gekies word
Impact of home-based HIV testing services on progress toward the UNAIDS 90-90-90 targets in a hyperendemic area of South Africa.
CAPRISA, 2019.Abstract available in PDF
Misdiagnosis of HIV infection during a South African communityâbased survey : implications for rapid HIV testing.
CAPRISA, 2017.Abstract available in pdf
Bio-inspired computation: where we stand and what's next
In recent years, the research community has witnessed an explosion of literature dealing with the adaptation of behavioral patterns and social phenomena observed in nature towards efficiently solving complex computational tasks. This trend has been especially dramatic in what relates to optimization problems, mainly due to the unprecedented complexity of problem instances, arising from a diverse spectrum of domains such as transportation, logistics, energy, climate, social networks, health and industry 4.0, among many others. Notwithstanding this upsurge of activity, research in this vibrant topic should be steered towards certain areas that, despite their eventual value and impact on the field of bio-inspired computation, still remain insufficiently explored to date. The main purpose of this paper is to outline the state of the art and to identify open challenges concerning the most relevant areas within bio-inspired optimization. An analysis and discussion are also carried out over the general trajectory followed in recent years by the community working in this field, thereby highlighting the need for reaching a consensus and joining forces towards achieving valuable insights into the understanding of this family of optimization techniques
The effect of graduated compression socks on calf muscle oxygenation of endurance athletes
Thesis (M Sport Sc)--Stellenbosch University, 2012.ENGLISH ABSTRACT: Compression socks (CS) are used as an ergogenic aid during and after exercise by many athletes
of elite and recreational status. The exact mechanism whereby CS affect performance and postexercise
recovery is not yet elucidated. Some research ascribes the beneficial effects to improved
lactate removal rates with CS. One hypothesis is that CS improve venous return and thereby
remove the lactate from the tissue to other tissues such as the liver, and the second hypothesis is
that the CS cause retention of the lactate within the muscle and therefore improve the oxidation of
the lactate within the muscle (Berry & McMurray, 1987).
The current study endeavoured to test the hypothesis set by Berry and McMurray (1987) by
measuring the effect of CS as well as flight socks (FS) on muscle oxygenation during exercise and
recovery in endurance trained runners and triathletes.
Eleven male endurance trained runners and triathletes (age = 34.8 ± 3.8 years, VO2max = 52.4 ± 7.1
mL.kg-1.min-1) participated in the study. They completed an incremental exercise test to exhaustion
to determine their maximal aerobic capacity (VO2max) and peak treadmill velocity (PTV). Then they
completed two 10 km treadmill running tests at 80 % of their PTV. During these two trials
participants wore either CS or FS; the order of treatment was randomly selected. A subset of the
study sample (n = 5) also completed a control test wearing only their ankle length sport socks
(NS). After these trials, participants completed a 60 minute passive recovery period in the seated
position while muscle oxygenation was measured.
Compression under the socks was measured at several anatomically determined measurement
points prior to the commencement of the exercise test, along with the determination of blood
haemoglobin concentration ([Hb]). During the exercise trials, blood lactate concentration ([BLa]),
skin temperature (ST),oxygen consumption (VO2), carbon dioxide production (VCO2), heart rate
(HR), and muscle oxygenation variables (oxy-haemoglobin (O2Hb), deoxy-haemoglobin (HHb),
tissue oxygenation index (TOI) and total haemoglobin index (nTHI)) was measured . During the 60minute passive recovery period, [BLa], ST, O2Hb, HHb, TOI, and nTHI measurements were
continued.
The results showed that there were differences in the pressure exerted between the two pressure
condition (CS and FS) at the posterior ankle, and under the elastic of the sock as well as on the
anterior calf at the level of greatest calf circumference. Differences in ST between the CS and NS
and the FS and NS conditions were found between the first four 2 km intervals of the exercise
protocol, but not during recovery.
No differences were found in [BLa] between the three different compression conditions during
either the exercise (p = 0.19) or recovery period (p = 0.63), as well as no differences in the
cardiorespiratory variables during exercise between the three different compression conditions
(VO2, p = 0.06; VCO2, p = 0.12; HR, p = 0.36). With regard to the muscle oxygenation variables, no
differences were found between the three compression conditions during exercise, however there
was a trend for lower oxygen utilization (HHb) during exercise in the NS condition (p = 0.57,
medium to large practical significance). There were also no differences in these variables (O2Hb, p
= 0.65; HHb, p = 0.57; TOI, p = 0.39; nTHI, p = 0.22) during recovery, although oxygen utilization
(HHb) showed a faster recovery rate with increasing external pressure.
From the results obtained, it seems that external compression caused a decrease in the blood flow
velocity within the muscle, thereby increasing oxygen diffusion rate. During exercise this did not
facilitate differences in [BLa], however, after the first 10 minutes of the recovery period, large
practical differences were found between the NS and both sock conditions, suggesting that the
increase in oxygen diffusion improved lactate clearance. This could support the hypothesis set by
Berry and McMurray (1987).AFRIKAANSE OPSOMMING: Kompressie sokkies (CS) word gereeld deur beide rekreasie- en elite atlete gebruik as ân
ergogeniese hulpmiddlel tydens oefening en herstel. Die presiese meganisme waardeur CS
prestasie en post-oefening herstel beĂŻnvloed is nog nie volledig verklaar nie. Sommige navorsing
skryf die voordelige effekte toe aan die vinniger herstel van laktaat in die sirkulasie. Daar is tans
twee hipoteses vir die meganisme waardeur CS laktaat verwydering verbeter. Die eerste hipotese
is dat CS die veneuse terugvoer verbeter en daardeur die laktaat van die weefsel verwyder en na
ander weefsels soos die lewer vervoer vir verwydering. Die tweede hipotese is dat CS veroorsaak
dat die laktaat in die spierweefsel teruggehou word wat dan tot gevolg het dat die laktaat in die
spier self deur middel van oksidasie verwyder word (Berry & McMurray, 1987).
Hierdie studie poog om Berry en McMurray (1987) se hipotese te toets deur die effek wat CS
sowel as vlugsokkies (FS) op spieroksigenasie het gedurende oefening en herstel in geoefende
uithouvermoë hardlopers en driekamp atlete vas te stel.
Elf ingeoefende langafstand hardlopers en driekampatlete (mans) (ouderdom = 34.8 ± 3.8 jaar;
VO2maks = 52.4 ± 7.1 mL.kg-1.min-1) het aan hierdie studie deel geneem. Die deelnemers het ân
inkrementele toets tot die punt van uitputting voltooi om hul maksimale aërobiese kapasiteit
(VO2maks) en piek trapmeul snelheid (PTV) vas te stel. Die elf deelnemers het ook twee 10 km
hardlooptoetse teen 80 % van hul PTV voltooi. Gedurende hierdie twee toetse het die deelnemers
Ăłf CS Ăłf FS gedra; die volgorde van die intervensie was lukraak aan hulle toegeken. ân Subgroep
van die steekproef (n = 5) het ook ân kontrole toets voltooi waartydens hulle hul eie enkelhoogte
sport sokkies (NS) gedra het. Aan die einde van die hardloop protokol het die deelnemers ân 60
minuut passiewe herstel periode in die sittende posisie voltooi terwyl spieroksigenasie gemeet is.
Kompressie onder die sokkies is voor die aanvang van die hardloop protokol by verskeie
anatomies gedefinieerde punte gemeet. Verder was die bloed hemoglobien konsentrasie ([Hb])
ook gemeet voor die hardloop protokol. Tydens die oefeningtoets is bloedlaktaat konsentrasie ([Hb]), veltemperatuur (ST), suurstof verbruik (VO2), koolstofdioksied produksie (VCO2), harttempo
(HR), sowel as spieroksigenasie veranderlikes (oksi-hemoglobien (O2Hb), deoksi-hemoglobien
(HHb), weefsel oksigenasie indeks (TOI), en totale hemoglobien indeks (nTHI)) gemeet.
Gedurende die 60 minuut passiewe hersteltydperk is [BLa], ST, O2Hb, HHb, TOI en nTHI metings
geneem.
Die resultate toon dat daar ân verskil is in die druk wat uitgeoefen word in die onderskeie
druktoestande (CS en FS) op die been by die posterior enkel en onder die rek van die sokkie,
sowel as op die anterior kuit waar die kuit die grootste omtrek het. Verdere verskille tussen die CS
en NS en die FS en NS toestande is in ST gevind in the eerste vier 2 km intervalle van die
oefeningtoets, alhoewel geen verskille tydens die herstelperiode gevind is nie.
Tydens beide die oefening (p = 0.19) en herstel (p = 0.63) protokol is geen verskille tussen die drie
kompressie toestande met betrekking tot [BLa] gevind nie. En so ook is daar geen verskille tussen
die onderskeie kompressie toestande in kardiorespiratoriese veranderlikes (VO2, p = 0.06; VCO2, p
= 0.12; HR, p = 0.36) tydens oefening gevind nie. Met betrekking tot spieroksigenasie
veranderlikes was daar geen verskil gevind tussen die drie kompressietoestande gedurende
oefening nie, alhoewel daar ân tendens was vir die NS toestand om tydens oefening minder
suurstofverbruik (HHb) (p = 0.57, medium tot groot praktiese effek) te lewer. So ook gedurende
herstel is daar geen verskil in hierdie veranderlikes (O2Hb, p = 0.65; HHb, p = 0.57; TOI, p = 0.39;
nTHI, p = 0.22) gevind nie, alhoewel die suurstofverbruik (HHb) vinniger na die basislyn herstel het
met ân toename in druk.
Die resultate toon dat eksterne kompressie ân afname in die bloedvloei tempo in die spier
veroorsaak wat dan ân verlengde suurstof diffusie tyd veroorsaak. Hierdie verlengde suurstof
diffusie tyd het geen effek op [BLa] tydens oefening gehad nie, alhoewel daar na die eerste 10
minute van die herstelperiode ân groot praktiese verskil tussen die NS en sokkie toestande gevind
was in [BLa]. Hierdie verskil kan daarop dui dat die toename in suurstof diffusie verbeterde laktaat
verwydering tot gevolg het, wat dan die hipotese van Berry en McMurray (1987) ondersteun.Maste
Characterisation of the responsive properties of two running-specific prosthetic models
The need for information regarding running-specific prosthetic properties has previously been voiced. Such information is necessary to assist in athletes' prostheses selection.status: publishe