Assignment (MPhil)--University of Stellenbosch, 2003. / ENGLISH ABSTRACT: The mechanisms of blood flow (BF) control to skeletal muscle during dynamic
exercise are still not clearly understood. The paraplegic subject (P) has reduced
sympathetic innervation to the lower limbs. The current study was designed to focus
on the contribution of neural control, specifically the sympathetic nervous system
(SNS), as part of the central vascular mechanism to skeletal muscle BF during
dynamic exercise. Aims: We studied BF parameters in P vs. able-bodied subjects
(AB) to determine whether the paraplegic can serve as a model for assessing the
contribution of the SNS to changes in active vs. inactive muscle BF during exercise.
Further questions addressed include: the influence of level of fitness on resting and
exercise BF, how lesion level affects BF control in the paraplegic, the 'muscle pump'
theory and its hypothesized role in exercise hyperemia and whether blood pooling
occurs in the legs of paraplegics. Method: Noninvasive duplex Doppler studies of the
large conduit arteries (brachial and common femoral) were performed on 10 elite
paraplegic athletes (EP), 10 sedentary paraplegics (SP) en 10 sedentary able-bodied
subjects (AB). The paraplegic groups were further subdivided by lesion level with T6
being the critical level. Tests were carried out at rest and after 2 bouts of arm
ergometer exercise: a maximal incremental test and 3 minutes at 75% of maximal.
Diameter, mean velocity, pulsatile index and blood flow were measured/calculated.
Results: Resting heart rate was significantly higher in the paraplegic groups (EP = 80
bpm ± 10, SP = 83 bpm ± 12) vs. the AB group (69 bpm ± 7), p < 0.05. Resting
diameter in the common femoral artery (CFA) was similar in EP (5.93 mm ± 1.54)
and SP (6.52 mm ± 0.95), but significantly lower than in AB (7.87 mm ± 1.38), p <
0.05. Similar resting pulsatile index (PI) in the CFA were contrary to that previously
reported, casting doubt on venous blood pooling theories. Post-exercise values need to be interpreted with caution in view of the large resting differences in CFA diameter.
Percentage change values are therefore more appropriate. These differences were not
statistically significant, but may suggest interesting trends. Large variability existed
for most resting and post-exercise values. Conclusion: The paraplegic subject is an
ideal model for the study of the influence of the SNS on blood supply to exercising
skeletal muscle. The difference in CFA diameter at rest in the paraplegic vs. the AB
group confirms previous results and is probably due to structural/non-physiological
changes. Our observation that the BA and CFA diameters in EP and SP subjects do
not differ significantly at rest, suggests that training does not have a spillover
vasomotor effect on lower limb conduit arteries in paraplegia. Similar BF and PI
values post-exercise in the SP and AB groups challenge the muscle pump theory. The
SNS has an important role in the control of skeletal muscle blood flow - both at rest
(vascular tone) and during exercise (redistribution). Suggestions for future research
are made. / AFRIKAANSE OPSOMMING: Die meganismes betrokke by die beheer van bloedvloei (BV) gedurende dinamiese
oefening is nog onduidelik. Die parapleeg (P) het verminderde simpatiese innervasie
na die onderste ledemate. Die huidige studie fokus op die bydrae van die simpatiese
senuwee sisteem (SSS), as deel van die sentrale vaskulêre meganisme, tot skeletale
spier BV tydens dinamiese oefening. Doelstellings: Ons het BV parameters in P vs.
nie-gestremde proefpersone (kontrole) bestudeer om vas te stelof die parapleeg as
model gebruik kan word om die bydrae van die SSS tot veranderings in die BV in
aktiewe- en onaktiewe spiere gedurende oefening, te ondersoek. Verdere aspekte wat
ondersoek is, sluit in: die invloed van tiksheidvlak ten opsigte van rustende en
oefenings BV, of die verlammingsvlak by die parapleeg BV kontrole beïnvloed, die
'spierpomp-teorie' en sy hipotetiese rol in oefeninghiperremie, asook die vraag of
bloedsaamstorting in die bene van parapleë plaasvind. Metode: Nie-indringende
duplex Doppler studies van die groot geleidingsarteries (bragiaal [BA] en gemene
femoral [CFA]) is by 10 elite paraplegiese atlete (EP), 10 sedentêre parapleë (SP) en
10 sedentêre nie-gestremde proefpersone (AB) uitgevoer. Die paraplegiese
proefpersone is verder onderverdeel deur die vlak van T6 as kritiese verlammingsvlak
te gebruik. Toetse is tydens rus en na 2 arm-ergometer oefeningsessies uitgevoer: een
maksimale inkrementeie toets en een van 75% van maksimum intensiteit. Deursnit,
gemiddelde vloeispoed, pulsatiewe indeks en bloedvloei is gemeet en/of bereken.
Resultate: Rustende hartspoed was beduidend hoër in die paraplegiese groepe (EP =
80 slaelminuut ± 10 en SP = 83 slm ± 12) vs. die AB groep (69 slm ± 7), p < 0.05.
Rustende deursnit in die gemene femorale arterie (CFA) was dieselfde in EP (5.93
mm ± 1.54) en SP (6.52 mm ± 0.95), maar beduidend laer as in AB (7.87 mm ± 1.38),
p < 0.05. Die feit dat rustende pulsatiewe indeks (PI) in die CFA dieselfde in albei groepe was, laat twyfelontstaan oor die veneuse bloedopdammings teorieë soos
weergegee in die literatuur. Na-oefeningswaardes moet omsigtig evalueer word met
inagneming van die groot rustende verskille in CFA deursnit. Persentasieverskilwaardes
is dus meer toepaslik. Hierdie veskille was nie statisties beduidend nie, maar
suggereer interessante tendense. Groot variasie het voorgekom vir beide rustende en
na-oefenings waardes. Gevolgtrekking: Die parapleeg is 'n ideale model vir studies
om die invloed van die SSS op bloedvloei aan aktiewe skeletale spier te bestudeer.
Die verskil in rustende CFA deursnit in die parapleeg vs. die AB groep bevestig
vorige resultate en is waarskynlik te wyte aan strukturele, nie-funksionele
veranderinge. Ons bevindinge dat die BA en CFA deursneë nie beduidend verskil in
die SP en EP groep gedurende rus nie, dui daarop dat gereëlde oefening nie 'n oorloop
vasomotor effek op die onderste ledemate in die parapleeg het nie. Die feit dat daar
geen verskil aangetoon kon word tussen BV en PI waardes na-oefening in die SP en
AB groepe, betwis die spierpomp teorie.
Die studie toon dat die SSS 'n belangrike rol in die beheer van skeletale spier
bloedvloei speel - beide met rus (vaskulêre tonus) en gedurende oefening
(herdistribusie). Voorstelle vir toekomstige navorsing word gemaak.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/49783 |
| Date | 12 1900 |
| Creators | Scriba, E. W. (Ernst Wolfgang) |
| Contributors | Myburgh, K. H., Van Rooyen, J., Stellenbosch University. Faculty of Education. Dept. of Sport Science. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | Unknown |
| Type | Thesis |
| Format | 60 p : ill. |
| Rights | Stellenbosch University |
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