The 2 in VO2 is in subscript. / Thesis (MSc)--Stellenbosch University, 2000. / ENGLISH ABSTRACT: Please see fulltext for abstract / AFRIKAANSE OPSOMMING: Sien asb volteks vir opsomming

Thesis (M Sport Sc)--Stellenbosch University, 2011. / ENGLISH ABSTRACT: This study investigated the optimal training load required for peak-power production in two types of exercises, namely an Olympic-type and a ballistic exercise. The hang clean and the squat jump were selected to represent these two types of exercise. It was ascertained whether a change in strength levels and training status will have an effect on the optimal loads for peak-power production of rugby players. In addition, the influence that different playing positions have on power production was also investigated. Fifty-nine under-21 male rugby players (Mean Age 19.3yrs; SD ± 0.7yr) from two rugby academies, performed a maximal-strength test in the hang clean and squat, followed by a power test in the hang clean and squat jump with loads ranging from 30 to 90% of maximal strength (1RM). Testing was conducted in the pre-season phase and repeated during the inseason phase. Peak power for the hang clean was achieved at 90% 1RM in the pre-season and at 80% 1RM during the in-season. Peak power for the squat jump was achieved at 90% 1RM in the pre-season. However, this location of the optimal loading was not significantly higher than that of the other loadings (60, 70 and 80% 1RM). During the in-season, peak power for the squat jump was reached at 90% 1RM. Here again, the optimal-loading location was not significantly higher than that of the other loadings (50, 60, 70 and 80% 1RM). It was concluded that the optimal load for power production is 90% 1RM for the hang clean and 60-90% for the squat jump. It was found that an improvement in strength levels of the subjects affected both peak-power production and the optimal load in both exercises. During the in-season peak power in the hang clean was reached at 80% 1RM, and at 50% 1RM for the squat jump. There were no significant differences in the performances of subjects from different playing positions (forwards versus backline players). In the hang clean, peak-power production seems to be reliant on increased strength and results in peak-power output at high loads. The squat jump, on the other hand, is more reliant on velocity due to its ballistic nature and is possibly better suited to developing power at lighter loadings. Because it produces peak power at a lower percentage load than the hang clean, the squat jump could be more effective in power development for players who are inexperienced in power training. Long-term exercise periodisation in power training can therefore be employed progressively from simpler exercises (e.g., squat jump) using only the legs, to more complex exercises (e.g., Olympic-lifting) that involve the whole body. This study confirmed that the specific requirements of different sport codes should be considered meticulously before selecting and prescribing exercises and loads for power-training programmes. / AFRIKAANSE OPSOMMING: Die hooffokus van hierdie studie was op die optimale oefenlading wat vereis word vir die produsering van piek-profkrag tydens die uitvoering van twee tipes oefening, naamlik ’n Olimpiese- en ’n ballistiese oefening. Die hang clean en die squat jump is geselekteer om bogenoemde twee tipes oefening te verteenwoordig. Daar is bepaal of ’n verbetering van die krag-vlakke en oefenstatus van rugbyspelers ’n invloed het op die optimale ladings vir piek-plofkrag ontwikkeling. Verder is die moontlike rol van verskillende speelposisies ondersoek. Nege-en-vyftig onder-21 mans-rugbyspelers (M-ouderdom 19.3jr; SD ± 0.7jr) vanuit twee rugbyakademies het ’n maksimale-krag toets in die hang clean en squat uitgevoer. Dit is opgevolg deur ’n plofkrag-toets in die hang clean en squat jump met ladings wat gewissel het van tussen 30 en 90% van maksimale werkverrigting (1RM). Toetsing het plaasgevind in die voor-seisoen fase en is herhaal tydens die daaropvolgende speelseisoen. Piek-plofkrag vir die hang clean is bereik tydens ’n oefenlading van 90% 1RM in die voor-seisoen en by 80% 1RM later in die speelseisoen. Piek-plofkrag vir die squat jump is behaal by 90% 1RM in die voor-seisoen fase. Hierdie optimale lading-lokasie was egter nie beduidend hoër as by die ander ladings van 60, 70 en 80% 1RM nie. Tydens die speelseisoen is piek-plofkrag bereik in die squat jump by 90% 1RM. Die optimale lading-lokasie was weereens nie beduidend hoër as by die ander ladings van 50, 60, 70 en 80% 1RM nie. Daar is tot die gevolgtrekking gekom dat die optimale oefenlading vir die ontwikkeling van piek-plofkrag vir die hang clean 90% 1RM is, en 60% vir die squat jump. Daar is ook gevind dat ’n verbetering in kragvlakke van die toetslinge, beide piek-plofkrag-produksie en die optimale oefenbelading in albei oefeninge beïnvloed. Tydens die speelseisoen is piek-plofkrag behaal in die hang clean by 80% 1RM, en by 50% 1RM in die squat jump. Geen beduidende verskille in werkverrigting is gevind tussen toetslinge uit verskillende speelposisies (voorspelers versus agterlyn-spelers) nie. Dit blyk dat in die hang clean, die produksie van plofkrag beïnvloed word deur ’n verbetering in krag en dat dit tot hoër optimale ladings vir piek-plofkrag produksie lei. Die squat jump, in teenstelling, is meer afhanklik van snelheid en is moontlik beter geskik vir die produsering van plofkrag teen ligter oefenladings. Omdat die squat jump piek-plofkrag genereer teen laer ladings as die hang clean, kan dit meer effektief wees vir spelers met gebrekkige ervaring in krag-oefening. Lang-termyn oefen-periodisering in plofkrag-oefening kan gevolglik progressief aangewend word vanaf eenvoudiger oefeninge (bv. squat jump), waar slegs die bene gebruik word, tot meer komplekse oefeninge (bv. Olimpiese-gewigoptel) waar die hele liggaam betrek word. Hierdie studie bevestig dat die spesifieke vereistes van verskillende sportkodes deeglik oorweeg moet word alvorens oefeninge en ladings geselekteer en voorgeskryf word vir plofkrag-programme.

Thesis (M Sport Sc (Sport Science))--University of Stellenbosch, 2009. / ENGLISH ABSTRACT: It is well-known that acute and chronic aerobic and resistance exercise results in decreased blood pressure (BP) in hypertensive individuals. There is little evidence that water exercise has a similar effect on BP response. There is also no certainty regarding the magnitude and duration of post exercise hypotension (PEH) after either land or water-based exercise. Most studies were also performed under controlled laboratory conditions and very few characterised the PEH response under real life conditions. The current study endeavoured to examine the magnitude and duration of PEH after an acute session of water- and land-based exercise during free living conditions in persons with mild to moderate hypertension. Twenty-one men and women (aged 52 ± 10 years) volunteered for the study. All participants were pre-hypertensive or hypertensive. Participants completed a no exercise control session, a water exercise session and a combined aerobic and resistance land exercise session in random order. After all three sessions, participants underwent 24 hour monitoring using an Ergoscan ambulatory BP monitoring device. Systolic blood pressure (SBP), diastolic blood pressure (DBP), mean arterial pressure (MAP) and heart rate (HR) were monitored to determine changes from resting values after each session and to compare the PEH responses between land and water exercise. Overall, the land exercise treatment caused a 3.6 mmHg lower average SBP over 24 hours than the control treatment (P = 0.04). The average difference over 24 hours between the water and control treatments was 2.2 mmHg and between land and water exercise it was 1.5 mmHg (P > 0.05). During daytime, both land and water exercise resulted in significantly lower SBP (12.7 and 11.3 mmHg) compared to the control session (2.3 mmHg). The PEH response lasted for 24 hours after land exercise and nine hours after water exercise. There was no difference in the daytime DBP for the three treatments (P > 0.05). Although all three groups showed significant reductions during night time, both exercise treatments showed greater nocturnal falls in SBP, DBP and MAP than the control treatment. / AFRIKAANSE OPSOMMING: Dit is alombekend dat akute en chroniese aërobiese- en weerstandsoefening tot ‘n afname in bloeddruk (BD) lei in persone met hipertensie. Daar is egter min getuienis dat wateroefening dieselfde effek op die bloeddruk respons het. Daar is ook nie sekerheid oor die grootte en duur van post-oefening hipotensie na water- of landoefening nie. Die meeste studies is onder gekontrolleerde laboratorium omstandighede gedoen en min resultate is beskikbaar onder alledaagse lewensomstandighede. Die huidige studie het gepoog om die grootte en duur van die post-oefening hipotensie respons in persone met ligte tot matige hipertensie onder alledaagse omstandighede na ‘n akute sessie van water- en landgebaseerde oefening te ondersoek. Een-en-twintig mans en vrouens (ouderdom 52 ± 10 jaar) het ingewillig om aan die studie deel te neem. Alle deelnemers was hipertensief of pre-hipertensief. Alle deelnemers het ‘n kontrolesessie, ‘n wateroefeningsessie en ‘n gekombineerde aërobiese en weerstands landoefensessie, in lukrake volgorde, voltooi. Na elke sessie het die deelnemers 24 uur bloeddrukmonitering met ‘n Ergoscan wandelende bloeddruk monitor ondergaan. Sistoliese bloeddruk (SBD), diastoliese bloeddruk (DBD), gemiddelde arteriële bloeddruk en harttempo (HT) is gemonitor om die veranderinge vanaf rustende waardes na elke sessie te bepaal en om die hipotensiewe respons na land- en wateroefening te vergelyk. Landoefening het ‘n 3.6 mmHg laer gemiddelde SBD oor 24 uur tot gevolg gehad in vergelyking met die kontrolesessie (P = 0.04). Die gemiddelde verskil oor 24 uur tussen die water- en kontrolesessies was 2.2 mmHg en 1.5 mmHg tussen die land en water oefensessies (P > 0.05). Gedurende die dag het beide die land- and wateroefening gelei tot beduidende laer SBD (12.7 en 11.3 mmHg) in vergelyking met die kontrolesessie (2.3 mmHg). Die post-oefening hipotensie het 24 uur geduur na die landoefening en nege uur na die wateroefening. Daar was geen verskil in DBD gedurende die dag tussen die drie groepe nie (P > 0.05).

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.

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 ‘n ergogeniese hulpmiddlel tydens oefening en herstel. Die presiese meganisme waardeur CS prestasie en post-oefening herstel beïnvloed 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 ‘n 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 óf CS óf FS gedra; die volgorde van die intervensie was lukraak aan hulle toegeken. ‘n Subgroep van die steekproef (n = 5) het ook ‘n kontrole toets voltooi waartydens hulle hul eie enkelhoogte sport sokkies (NS) gedra het. Aan die einde van die hardloop protokol het die deelnemers ‘n 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 ‘n 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 ‘n 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 ‘n toename in druk. Die resultate toon dat eksterne kompressie ‘n afname in die bloedvloei tempo in die spier veroorsaak wat dan ‘n 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 ‘n 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.

This study examined the effect of vitamin B-6 supplementation and exhaustive submaximal exercise on plasma catecholamine concentrations, and the relationship between plasma catecholamines and fuel use, heart rate and oxygen consumption. Five trained men (age= 18-35 years; V0₂max=53 ml 0₂/kg/min.) participated in two controlled dietary periods that were identical except for the addition of 20 mg/d pyridoxine (PN) supplementation during the second period. On the seventh morning of each period, fasted subjects exercised to exhaustion on a cycle ergometer at 74.5% ± 7.8 V0₂max. Blood was drawn pre-exercise (twice), 60 minutes into exercise, immediately post-exercise and 60 minutes post-exercise. Plasma was analyzed for norepinephrine, epinephrine, glucose, pyridoxal 5'-phosphate (PLP), lactic acid, glycerol and free fatty acids (FFA). Heart rate and oxygen consumption were measured pre-exercise and at 10-minute intervals during exercise. Mean plasma PLP concentration was significantly higher during the supplemented versus the nonsupplemented trial at all time points. There were no statistically significant differences in mean plasma catecholamine concentrations or mean plasma fuel concentrations between the nonsupplemented and supplemented trials at any of the time points examined. There were significant changes in the mean plasma concentrations of norepinephrine, lactic acid, glycerol and FFA over time in both trials. Respiratory exchange ratios (R) were higher during the supplemented trial compared to the nonsupplemented trial, but the differences did not attain statistical significance. There were no significant differences in mean exercise times to exhaustion or mean heart rates between the trials. The overall mean oxygen consumption during exercise was consistently higher during the supplemented versus the nonsupplemented trial and the difference attained significance (p=0.016) at one time point (10 min.). The mean oxygen consumption during rest was lower during supplementation versus nonsupplementation, but the difference was not statistically significant. The percent plasma volume change (PVC) was significantly greater at post-exercise, relative to pre-exercise, during the supplemented versus the nonsupplemented trial. The percent PVC also increased significantly over time during the supplemented but not the nonsupplemented trial. These results suggest that 20 mg/d of vitamin B-6 supplementation does not effect plasma catecholamine concentrations, fuel utilization or heart rate at rest or during submaximal exercise to exhaustion. The results may suggest a higher oxygen consumption during exhaustive exercise after PN supplementation. / Graduation date: 1996

Three investigations were conducted using pulsed Doppler echocardiography (PDE) and oxygen consumption to non-invasively determine the relationship between hemodynamic and metabolic variables from rest through submaximal and maximal exercise in early adolescent males. In the first study, interinvestigator and day-to-day variability of cardiac output measurements at rest and during exercise determined by PDE were analyzed in six junior high school age boys. Four Doppler-derived variables (cardiac output, cardiac index, stroke volume, and stroke index) were not different when calculated by independent investigators and showed the same interinvestigator variability from rest through submaximal and maximal exercise as has been reported at rest in previous validation studies. There was a slight but statistically significant increase in the absolute values of the above hemodynamic variables and simultaneously collected metabolic variables during a second identical test conducted approximately nine days later. A faster adjustment to increasing workrates in the second test could explain this latter finding since supine cycle ergometry is not as familiar an activity as more frequently used modes of exercise testing. It is concluded that hemodynamic measurements using PDE exhibit the same acceptable variability throughout exercise as has been previously demonstrated at rest. In the second study, PDE was used to determine rapid serial measurements of cardiac output during a rapid loading supine cycle ergometer exercise test in twenty-two junior high school age boys. These measurements were compared to simultaneoulsy determined measurements of oxygen consumption. Cardiac output adjusted faster to each new workrate than oxygen consumption. Further analysis of these responses revealed that increases in heart rate (as opposed to stroke volume) were responsible for this rapid adjustment. It is concluded that there is an uncoupling and recoupling of these normally closely related hemodynamic and metabolic variables during the transitional periods between increasing levels of steady-state supine exercise. In the final study, gradual loading and rapid loading supine cycle ergometer protocols were compared in fifteen junior high school age boys. Maximal metabolic measurements and heart rate from each test were not different. Maximal PDE-derived measurements of cardiac output, cardiac index, stroke volume, and stroke index were slightly, but significantly, higher in the gradual loading protocol. It is concluded that a more complete adjustment of cardiac output (reflected by stroke volume) to maximal supine exercise occurs in a more gradual loading protocol than in a rapid loading protocol.

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