Thesis (PhD)--University of Stellenbosch, 2005. / ENGLISH ABSTRACT: Skeletal muscle adapts to stimuli by modifying structural and metabolic protein expression.
Furthermore, a muscle group may vary within itself to accommodate specialisation in regions.
Structural and metabolic characteristics of an individual are regulated partly by genotype, but
contraction duration and intensity may play a greater role in muscle phenotype. The aims of this
dissertation were to investigate: structural and metabolic regionalisation in a muscle group, possible
relationships between training volume and intensity and hybrid fibres, muscle characteristics of
athletes from two different ethnic groups, and muscle adaptation in already well-trained athletes
subjected to high intensity interval training.
Myosin heavy chain (MHC) isoform content and citrate synthase (CS) activities were measured in
the Quadriceps femoris (QF) muscle of 18 female rats. Muscle was divided into superficial, middle
and deep, distal, central and proximal parts. MHC IIb and IIx were more abundant in superficial
regions (P < 0.05) with low CS activities compared to deeper parts. Isoform content varied along the
length of deep regions. This study showed that the QF has regional specialisation. Therefore,
standardisation of sampling site is important.
Hybrid fibre proportions in muscle biopsies of 12 middle distance runners and 12 non-runners were
investigated. MHC IIa/IIx correlated with training volume/week in runners (r = -0.66, P < 0.05) and
MHC IIa/IIx correlated with exercise hours/week in non-runners (r = -0.72, P < 0.01). Average
preferred racing distance (PRDA) correlated better with MHC IIa/IIx in runners (r = -0.85, P <
0.001). MHC IIa/IIx may therefore be more closely related to exercise intensity than previously
thought.
Fibre type characteristics and performance markers were investigated in 13 Xhosa and 13 Caucasian
distance runners, matched for performance, training volume and PRDA. Xhosa runners had less
MHC I and more MHC IIa fibres in muscle biopsies than Caucasian runners (P < 0.05). Xhosa
runners had lower plasma lactate at 80% peak treadmill speed (PTS) (P < 0.05), but higher lactate
dehydrogenase (LDH) (P < 0.01) and phosphofructokinase (P = 0.07) activities in homogenate
muscle samples. LDH activities in MHC I (P = 0.05) and IIa (P < 0.05) fibre pools were higher in
Xhosa runners. Xhosa athletes may thus have a genetic advantage or they may have adapted to
running at a higher intensity.
Six weeks of individually standardised high intensity interval treadmill training (HIIT) were
investigated in 15 well-trained runners. PTS increased after HIIT (P < 0.01), while maximum
oxygen consumption (VO2max) only showed a tendency to have increased as a result of HIIT (P = 0.06). Sub-maximal tests showed lower plasma lactate at 64% PTS (P = 0.06), with lower heart
rates at workloads from 64% to 80% PTS (P < 0.01) after HIIT. No changes were observed for
cross-sectional area, capillary supply and enzyme activities in homogenates muscle samples. LDH
activity showed a trend (P = 0.06) to have increased in MHC IIa pools after HIIT. Higher HIIT
speed was related to decreases in MHC I fibres, but increases in MHC IIa/IIx fibres (r = -0.70 and r
= 0.68, respectively, P < 0.05). Therefore, HIIT may alter muscle fibre composition in well-trained
runners, with a concomitant improvement in performance markers. / AFRIKAANSE OPSOMMING: Skeletspier kan adapteer deur strukturele en metaboliese protein ekspressie te verander as gevolg
van stimulante. ‘n Spiergroep kan ook intern verskil om spesialisering in spierdele toe te laat.
Strukturele en metaboliese karaktereienskappe van ‘n individu word deels gereguleer deur gene,
maar kontraksie tydperk en intensiteit mag ‘n groter rol speel in spierfenotipe. Die doelwitte van
hierdie tesis was om ondersoek in te stel in: strukturele en metaboliese eienskappe in
spiergroepstreke, moontlike verhoudings tussen oefeningsvolume of intensiteit en baster vesels,
spier eienskappe in atlete van twee etniese groepe, en spier adaptasie in goed geoefende atlete
blootgestel aan hoë intensiteit interval oefening.
Miosien swaar ketting (MSK) isovorm inhoud en sitraat sintase (SS) aktiwiteite is gemeet in die
Quadriceps femoris (QF) spier van 18 wyfie rotte. Spiere was opgedeel in oppervlakkig, middel en
diep, asook distaal, sentraal en proksimale dele. MSK IIb en IIx was meer oorvloedig in
oppervlakkige dele (P < 0.05) met lae SS aktiwiteite in vergelyking met dieper dele. Isovorm
inhoud het ook verskil oor die lengte van diep dele. Dus bevat die QF gespesialiseerde streke en is
die area van monsterneming belangrik.
Baster vesel proporsies is ondersoek in spiermonsters van 12 middel afstand hardlopers en 12 niehardlopers.
MSK IIa/IIx van hardlopers het met oefeningsvolume/week gekorreleer (r = -0.66, P <
0.05), asook MSK IIa/IIx van nie-hardlopers met oefeningsure/week (r = -0.72, P < 0.01).
Gemiddelde voorkeur wedloop afstand (VWAG) het beter met MSK IIa/IIx gekorreleer in
hardlopers (r = -0.85, P < 0.001). MSK IIa/IIx mag dus meer verwant wees aan oefeningsintensiteit.
Veseltipe eienskappe en prestasie merkers was ondersoek in 13 Xhosa en 13 Caucasian langafstand
atlete, geëweknie vir prestasie, oefeningsvolume en VMAG. Xhosa hardlopers het minder tipe I en
meer tipe IIA vesels in hul spiermonsters gehad as die Caucasian hardlopers (P < 0.05). Xhosa
hardlopers het laer plasma laktaat by 80% van hul maksimale trapmeul spoed (MTS) (P < 0.05),
maar hoër laktaat dihidrogenase (LDH) (P < 0.01) en fosfofruktokinase (P = 0.07) aktiwiteite in
homogene spiermonsters gehad. LDH aktiwiteite in MSK I (P = 0.05) en IIa (P < 0.05)
veselbondels was hoër in Xhosa hardlopers. Xhosa atlete mag dus ‘n genetiese voorsprong geniet, of
hulle het geadapteer om by hoër intensiteite te hardloop.
Ses weke van geïndividualiseerde gestandardiseerde hoë intensiteit interval trapmeul oefening
(HIIT) was ondersoek in 15 goed geoefende hardlopers. MTS het verhoog na HIIT (P < 0.01), en
maksimale surrstof verbruik (VO2max) het ‘n neiging getoon om te verhoog het na HIIT (P = 0.07).
Submaksimale toetse het laer plasma laktaat by 64% MTS getoon (P = 0.06), met laer harttempos by werkladings 64% tot 80% MTS (P < 0.01). Geen veranderings was gemerk vir deursnit area,
kapillêre toevoer en ensiem aktiwiteite in homogene spiermonsters nie. LDH aktiwiteit het ‘n
neiging getoon om te verhoog het (P = 0.06) in MSK IIa veselbondels na HIIT. Hoër HIIT snelhede
was verwant aan ‘n daling in MSK I vesels, maar ‘n verhoging in MSK IIa/IIx vesels (r = -0.70 en r
= 0.68, respektiwelik, P < 0.05). HIIT mag dus spier veseltipe verander in goed geoefende
hardlopers, met gevolglike verbetering in prestasie merkers.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/16517 |
| Date | 10 1900 |
| Creators | Kohn, Tertius A. |
| Contributors | Myburgh, Kathryn H., Rautenbach, Marina, University of Stellenbosch. Faculty of Science. Dept. of Biochemistry. |
| Publisher | Stellenbosch : University of Stellenbosch |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | vii, 215 leaves : ill. (some col) |
| Rights | University of Stellenbosch |
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