Limiting factors to high intensity exercise : the role of intramuscular pH and skeletal muscle buffering

Mannion, AF

Abstract

Within the context of a metabolic model of fatigue, formulated from a review of the
literature, a decrease in intramuscular pH was identified as a potential limiting factor
to the performance of high intensity exercise (HIE). This suggested a role for
skeletal muscle buffering (B) in retarding the intramuscular acidosis typically
incurred during HIE. Previous studies on human muscle, were largely unable to
confirm this role, partly due to the lack of a clearly defined and consistently utilised
method of measurement of B. The validity of the procedures currently employed in
the determination of B was therefore investigated, revealing that many of the
individual differences in B, previously attributed physiological significance, may
have originated from inappropriate methodology.
In a cross-sectional examination of the vastus lateralis muscle of young, active
individuals, low correlations (p<0.05) between the muscle carnosine concentration
([CAR]) and in the 'in vitro B ' (Bvit) (r=0.30), and between either [CAR] or Bvit
and the % type II fibre area were observed. An elevated Bvit was shown to be of
importance in minimising the decrement in pH during HIE, but did not per se
permit the accumulation of a higher muscle lactate concentration, or allow for an
enhanced HIE performance; these factors were more dependent on the % type II
fibre area. The muscle pH, following dynamic HIE was highly variable between
individuals, and showed a significant (p<0.05) negative correlation with the % type
II fibre area.
16 weeks of isokinetic training of the quadriceps resulted in significant
improvements (p<0.05) in dynamic HIE performance with no concomitant
improvements in [CAR] or Bvit..
The data suggest that the muscle buffer value per se, is not a major limiting
factor to HIE, and that rather, the glycolytic capacity and pH tolerance of the
muscle may be the more important factors to consider.

Citation

Mannion, A. Limiting factors to high intensity exercise : the role of intramuscular pH and skeletal muscle buffering. (Thesis). Salford : University of Salford

• Thesis Type: Thesis
• Deposit Date: Oct 3, 2012
• Award Date: Jan 1, 1990