Transcript A *functional biopsy* of muscle properties in sprinters

A “functional biopsy” of muscle
properties in sprinters and
distance runners
Charlie, Kathleen, Diana, Victoria
Why did we choose this paper?
LAB EXPERIMENT
-Measured Sprinter vs. Long Distance Runner
-Muscle Group: Tibialis Anterior and Gastrocnemius
-Tibialis Anterior was more active in Sprinting from EMG
results
Curious about learning more about sprinting vs. long
distance running.
The metabolic differences between type I and type II
muscle fiber is on the order of 2-3 fold
Type I
● Slow
Twitch
● Aerobic
Type II
● Fast Twitch
● Anaerobic
Tibialis Anterior and Dorsiflexion
Broad Overview of Paper
Fast twitch (Type II) and slow twitch (Type I) represent extremes in
muscle specialization
Question: Do sprinters and distance runners have this extreme
specialization in muscle fibers?
How did they examine this?
Use in vivo means to measure differences in enzyme activities
Methods
● Ten sprinters and seven
distance runners (18-22)
● Force of participant ankle
dorsiflexion was studied at
end of season
● Spectra obtained
throughout experimental
protocol.
Isometric Exercise: Ischemic/Aerobic
Aerobic
> 60s of aerobic rest
> 420s of aerobic exercise
> 288s of aerobic recovery
Ischemic
> 300s ischemic rest
> 90-120s of ischemic exercise
Isometric ballistic contractions, and full
recruitment of all muscle fibers.
Ischemic Exercise, Why?
● Cuts off blood used for
production of ATP during
oxidative phosphorylation
● This control made it possible
to quantify contractile cost
later in the experiment
Magnetic resonance spectroscopy (MRS) can be used
to monitor intracellular metabolite and pH changes
during exercise
Measurements
● [PCr] = ATP buffer
o
PCr + ADP <-> Cr + ATP
● pH
o
Quantifies amount of glycolysis happening
Used these values and calculations to find:
● Contractile cost
● Oxidative capacity
● Glycolytic Flux
● Glycolytic ATP production
PCr and pH changes during ischemic
exercise
Take Home:
1) PCr concentration
decreased quicker in
Sprinters as opposed to
Distance runners
a) SPR have higher
contractile costs
1) pH is lower in Sprinters
a) More energy required
so more lactic acid
used
PCr recovery after steady state aerobic
exercise
Take Home:
1) PCr used quicker in
SPR
1) PCr resynthesized
more slowly in SPR
Expected if SPR has
increased contractile
costs and decreased
oxidative capacities
The contractile cost of ischemic exercise
and oxidative capacity differences
Take Home:
1) Contractile cost for
SPR runners is
significantly higher
than DIS runners
(47%) higher
1) DIS runners have
significantly higher
oxidative capacity
(52% higher)
Trade Offs?
Glycolytic flux during ischemic exercise is similar for
sprinters and long distance runners
Take Home:
1. The amount of ATP produced through
glycolysis is similar in both SPR and DIS
runners.
a. Runs counter to thinking
i. Inferring flux through isolated
enzymes difficult
Glycolytic ATP production as a percentage of
contractile ATP consumption is greater for distance
runners than for sprinters during ischemic exercise
Take Home:
Combination of contractile costs and glycolytic
flux
We find that DIS runners produce more ATP
for their contractile costs through glycolysis
compared to SPR
Conclusion
Expected:
SPR have Type II and DIS have Type I
Type II and Type I differ in metabolic rate greatly
Actual:
Difference in metabolism but not as a big enough difference as we might expect given
muscle fiber types.
Virtually all human muscles are a mixture of fast and slow twitch fibers.
Genetics or Training? Both!
Can’t change myosin fibers.
Can change capillary density and mitochondrial density.
Oh “Lorde,” a muscle song
They gathered up these volunteers
And had them do a couple of
exercises
Compared their findings to their peers’
And what they found held few
surprises
We know a bit about
fast twitch, slow twitch
Different types of fibers
ATP, PCr
Metabolic hustle
Is there a 2 to 3 fold difference?
I am lorde, ya ya ya
To test the Athletes:
Aerobic, Ischemic
chemical changes
Looking at contractions, Finding no abstractions
From the truth, we are a mix of types one and two.
Talkin’ ‘bout muscle fibers! (fibers)
Sprinters have more type II
Long distance runners more type I, but they use
both of them to run.
Testing dorsiflexion (flexion)
Do some fancy science stuff
And then they showed, they showed, they showed,
That they’re not that different
image sources (this slide won’t be presented, it’s just
for references for images)
http://www.ncl.ac.uk/magres/research/liver/
http://jap.physiology.org/content/94/3/1145
http://www.strength-and-power-for-volleyball.com/images/volleyball-genetics-muscle-fiber-3.jpg
http://www.victoris.ugent.be/en/Projects/muscle%20talent%20scan/
additional resources (also not presented)
MRS: http://www.mayfieldclinic.com/PE-MRspectroscopy.htm
Review Questions
1. How do ischemic and aerobic exercise differ? Why is
ischemic exercise used in this experiment?
2. What is the metabolic difference between Type I and
Type II muscle fibers? How does this metabolic
difference relate to twitch speed?
Oh “Lorde,” a muscle song
They gathered up these volunteers
And had them do a couple of exercises
Compared their findings to their peers’
And what they found held few surprises
We know a bit about
fast twitch, slow twitch
Different types of fibers
ATP, PCr
Metabolic hustle
Is there a 2 to 3 fold difference?
I am lorde, ya ya ya
To test the Athletes:
Aerobic, Ischemic
chemical changes
Looking at contractions
Finding no abstractions
From the truth, we are a mix of types one and two.
Something that rhymes with royals! (royals)
Sprinters have more type II
Long distance runners more type I, but they both
use them to run.
Let me be your ruler (ruler)
You can call me queen bee
And then they showed, they showed, they
showed,
That they’re not that different