Physiological determinants of climbing-specific finger endurance and sport rock climbing performance


MacLeod, D.; Sutherland, D.L.; Buntin, L.; Whitaker, A.; Aitchison, T.; Watt, I.; Bradley, J.; Grant, S.

Journal of Sports Sciences 25(12): 1433-1443

2007


The aim of the study was to examine several physiological responses to a climbing-specific task to identify determinants of endurance in sport rock climbing. Finger strength and endurance of intermediate rock climbers (n = 11) and non-climbers (n = 9) were compared using climbing-specific apparatus. After maximum voluntary contraction (MVC) trials, two isometric endurance tests were performed at 40% (s = 2.5%) MVC until volitional exhaustion ( continuous contractions and intermittent contractions of 10 s, with 3 s rest between contractions). Changes in muscle blood oxygenation and muscle blood volume were recorded in the flexor digitorum superficialis using near infra-red spectroscopy. Statistical significance was set at P < 0.05. Climbers had a higher mean MVC (climbers: 485 N, s = 65; non-climbers 375 N, s = 91) (P = 0.009). The group mean endurance test times were similar. The force-time integral, used as a measure of climbing-specific endurance, was greater for climbers in the intermittent test ( climbers: 51,769 N center dot s, s = 12,229; non-climbers: 35,325 N center dot s, s = 9724) but not in the continuous test ( climbers: 21,043 N center dot s, s = 4474; non-climbers: 15,816 N center dot s, s = 6263). Recovery of forearm oxygenation during rest phases ( intermittent test) explained 41.1% of the variability in the force -time integral. Change in total haemoglobin was significantly greater in non-climbers ( continuous test) than climbers (P = 0.023-40% test timepoint, P = 0.014-60% test timepoint). Pressor responses were similar between groups and not related to the force -time integral for either test. We conclude that musclere-oxygenation during rest phases is a predictor of endurance performance.

Journal
of
Sports
Sciences,
October
2007;
25(12):
1433
—1443
R
Routledge
Taylor
&Francis
Group
Physiological
determinants
of
climbing-specific
finger
endurance
and
sport
rock
climbing
performance
D.
MAcLEOD
1
,
D.
L.
SUTHERLAND%
L.
BUNTIN
1
,
A.
WHITAKER
2
,
T.
AITCHISON
3
,
I.
WATT',
J.
BRADLEY'',
&
S.
GRANT
1
'Institute
of
Biomedical
and
Life
Sciences,
2
Department
of
Mechanical
Engineering,
3
Department
of
Statistics,
University
of
Glasgow,
Glasgow
and
4
Department
of
Biological
Sciences,
University
of
Central
Lancashire,
Preston,
UK
(Accepted
28
July
2006)
Abstract
The
aim
of
the
study
was
to
examine
several
physiological
responses
to
a
climbing-specific
task
to
identify
determinants
of
endurance
in
sport
rock
climbing.
Finger
strength
and
endurance
of
intermediate
rock
climbers
(n
=
11)
and
non-climbers
(n
=
9)
were
compared
using
climbing-specific
apparatus.
After
maximum
voluntary
contraction
(MVC)
trials,
two
isometric
endurance
tests
were
performed
at
40%
(s
=2.5%)
MVC
until
volitional
exhaustion
(continuous
contractions
and
intermittent
contractions
of
10
s,
with
3
s
rest
between
contractions).
Changes
in
muscle
blood
oxygenation
and
muscle
blood
volume
were
recorded
in
the
flexor
digitorum
superficialis
using
near
infra-red
spectroscopy.
Statistical
significance
was
set
at
P
<
0.05.
Climbers
had
a
higher
mean
MVC
(climbers:
485
N,
s=
65;
non-climbers
375
N,
s=
91)
(P=
0.009).
The
group
mean
endurance
test
times
were
similar.
The
force—time
integral,
used
as
a
measure
of
climbing-specific
endurance,
was
greater
for
climbers
in
the
intermittent
test
(climbers:
51,769
N
s,
s=
12,229;
non-climbers:
35,325
N
s,
s=
9724)
but not
in
the
continuous
test
(climbers:
21,043
N
s,
s=
4474;
non-climbers:
15,816
N
s,
s=
6263).
Recovery
of
forearm
oxygenation
during
rest
phases
(intermittent
test)
explained
41.1%
of
the
variability
in
the
force
—time
integral.
Change
in
total
haemoglobin
was
significantly
greater
in
non-climbers
(continuous
test)
than
climbers
(P=
0.023
40%
test
timepoint,
P=
0.014
60%
test
timepoint).
Pressor
responses
were
similar
between
groups
and
not
related
to
the
force
time
integral
for
either
test.
We
conclude
that
muscle
re-oxygenation
during
rest
phases
is
a
predictor
of
endurance
performance.
Keywords:
Forearm
endurance,
isometric
exercise,
muscle
oxygenation,
pressor
response,
rock
climbing
Introduction
Rock
climbing
has
developed
into
a
mainstream
competitive
sport
(Oviglia,
2006).
This
growth
is
evidenced
by
the
rapid
increase
in
the
number
and
size
of
indoor
climbing
walls,
and
recorded
climbs
in
the
various
disciplines
of
climbing.
The
focus
of
the
new
disciplines
of
sport
climbing
and
bouldering
are
the
gymnastic,
athletic,
and
competitive
aspects
of
climbing
and
movement
on
rock
(Jones,
1991).
The
standard
of
climbing
of
the
world's
leading
athletes
has
risen
steadily
in
the
past
few
decades
as
new
training
methods
and
improved
facilities
have
been
developed
(Goddard
&
Neumann,
1993)
such
that
the
basic
biomechanical
demands
of
elite
rock
climbing
have
changed
and
continue
to
do
so.
Today's
hardest
climbs
feature
angles
up
to
and
greater
than
45°
beyond
vertical
(Goddard
&
Neumann,
1993).
On
such
overhanging
terrain,
the
legs
cannot
support
much
of
the
body
mass
in
the
vertical
direction;
they
can
only
push
the
body
along
the
plane
of
the
overhanging
surface.
As
the
angle
increases,
the
forces
exerted
increasingly
shift
to
the
smaller
muscles
of
the
upper
limbs.
Noe,
Quiane,
and
Martin
(2001)
observed
an
increased
reliance
on
upper
limb
support
from
43%
to
62%
of
total
body
weight
when
the
wall
angle
was
changed
from
vertical
to
10°
overhanging.
Climbers
have
recognized
that
finger
strength
is
a
central
component
of
climbing
performance
and
this
is
the
focus
of
rock
climbers'
training
regimes
(Goddard
&
Neumann,
1993;
Hurni,
2003;
Jones,
1991;
Morstad,
2000;
Sagar,
2001).
In
climbing,
the
fingers
produce
tension
on
a
hold
to
support
a
proportion
of
the
body
weight.
The
isometric
contraction
of
the
finger
flexors
of
each
hand
is
interrupted
intermittently
when
reaching
towards
the
next
hold.
Some
studies
have
suggested
Correspondence:
S.
Grant,
Institute
of
Biomedical
and
Life
Sciences,
University
of
Glasgow,
West
Medical
Building,
Glasgow
G12
8QQ,
UK.
E-mail:
ISSN
0264-0414
print/ISSN
1466-447X
online
©
2007
Taylor
&
Francis
DOI:
10.1080/02640410600944550
1434
D.
MacLeod
et
al.
that
finger
strength
is
a
determinant
of
performance
(Bollen
&
Cutts,
1993;
Grant,
Hynes,
Whitaker,
&
Aitchison,
1996).
However,
differences
in
methods
between
studies
have
resulted
in
conflicting
conclu-
sions
(Watts,
Newbury,
&
Sulentic,
1996).
Bouts
of
sport
climbing
last
for
several
minutes
with
sustained
periods
of
intermittent
isometric
contraction
in
the
finger
flexors
(Schadle-Schardt,
1998).
Studies
have
demonstrated
increased
finger
endurance
in
trained
climbers
(Ferguson
&
Brown,
1997)
and
forearm
fatigue
is
associated
with
falls
in
climbing
and
is
identified
by
climbers
as
a
key
performance
variable.
Watts
and
Drobish
(1998)
demonstrated
that
lactate
production
is
related
to
climbing
angle.
This
finding
is
supported
by
Mer-
mier,
Robergs,
McMinn,
and
Heward
(1997),
who
observed
that
lactate
production
is
related
to
climb-
ing
difficulty.
Several
physiological
variables
could
influence
endurance
performance
during
intermit-
tent
isometric
actions.
Increasing
central
arterial
blood
pressure
has
been
shown
to
improve
force
production
during
isometric
hand
contraction
(Wright,
McCloskey,
&
Fitzpatrick,
2000).
We
hypothesized
that
a
greater
pressor
response
during
a
climbing-specific
finger
endurance
task
would
improve
endurance
performance.
Other
adaptations
promoting
increased
intramuscular
blood
flow
both
during
contractions
and
relaxations
(while
reaching
to
the
next
hold)
could
also
be
important
determi-
nants
of
performance
(Ferguson
&
Brown,
1997).
Enhanced
blood
flow
might
result
from
an
increased
capillary
density,
enlargement
of
capillary
cross-
sectional
area
or
modifications
in
dilator
function
related
to
endothelial
change
(Delp,
1995;
Sinoway,
Mutch,
Minotti,
&
Zelis,
1986;
Smolander,
1994;
Snell,
Martin,
Buckey,
&
Blomqvist,
1987).
Despite
the
fact
that
the
flexors
of
the
fingers
are
perceived
to
have
an
important
role
in
climbing
performance,
there
is
very
little
information
on
the
finger
flexor
endurance
of
climbers
in
the
literature
and
it
appears
that
no
studies
have
investigated
forearm
oxygenation
in
trained
climbers
during
a
climbing-specific
finger
endurance
task.
We
hy-
pothesized
that
forearm
adaptations
in
climbers
distinguish
them
from
non-climbing
controls.
We
predicted
that
regular
participation
or
training
in
rock
climbing
would
result
in
increased
finger
flexor
strength
and
forearm
oxygenation
and
that
these
adaptations
would
promote
better
perfor-
mance
in
a
climbing-specific
endurance
test.
It
is
acknowledged
that
while
differences
between
trained
climbers
and
non-climbing
controls
might
be
attributed
to
training
adaptations,
there
is
the
possibility
that
any
differences
could
have
a
genetic
component.
The
aim
of
this
study
was
to
examine
several
physiological
responses
to
a
climbing-specific
task
to
identify
adaptations
of
trained
climbers
and
determi-
nants
of
endurance
performance.
Methods
Participants
Twenty
males
(mean
age
22.5
years,
s=
2.6)
participated
in
the
study,
of
whom
11
were
inter-
mediate
rock
climbers
and
9
were
non-hand-trained
healthy
controls.
The
researchers
tried
to
recruit
participants
of
similar
age
and
body
size.
The
climbers'
self-rated
ability
(best
"on-sight"
climbing
grade)
ranged
from
F6c
to
F7c
(mean
7a+)
on
the
French
scale.
On-sight
is
a
term
used
to
describe
an
ascent
of
a
route
at
the
first
attempt
with
no
rests
or
falls.
The
climbers
(mean
age
23.2
years,
s=
3.2)
had
a
mean
climbing
experience
of
5.3
years
(s=
1.9).
The
non-climbers
(mean
age
21.6
years,
s=
1.3
years)
did
not
participate
in
any
activities
requiring
finger
or
hand
strength.
The
climbers
were
involved
in
regular
climbing
or
climbing-specific
training
activities.
The
study
was
approved
by
the
University
of
Glasgow
ethics
committee
for
non-clinical
re-
search
involving
humans.
All
participants
provided
informed
consent
before
testing
and
completed
a
health
and
physical
activity
questionnaire
before
each
test
session.
Design
The
participants
undertook
three
test
sessions
at
least
48
hours
apart
to
ensure
adequate
recovery.
All
three
sessions
were
performed
at
the
same
time
of
day
1
hour)
to
limit
variations
in
performance
due
to
diurnal
patterns
and
were
completed
for
each
participant
within
a
3-week
period
to
avoid
variations
in
performance
due
to
training
effects.
At
the
first
session,
after
habituation,
the
participants
performed
maximal
voluntary
contraction
(MVC)
trials
and
two
isometric
endurance
tests
(see
below).
On
the
second
visit,
additional
MVC
tests
and
one
of
the
endurance
tests
were
performed.
At
the
third
session,
the
participants
performed
one
endurance
test.
The
participants
were
asked
not
to
drink
alcohol
the
night
before
testing
and
to
abstain
from
eating
in
the
hour
preceding
testing.
They
were
also
asked
not
to
train
heavily
the
day
before
testing.
Climbing-specific
apparatus
and
positioning
of
the
participant
Finger
strength
and
endurance
were
measured
using
apparatus
developed
at
the
University
of
Glasgow
(Grant
et
al.,
1996)
(Figure
1A).
It
was
designed
to
be
rock
climbing
specific,
simulating
as
closely
as
possible
the
mechanical
conditions
experienced
on
a
Finger
plate
attached
to
strain
gauge
.--
"Open
crimp"
position
with
fingers
flexed
at
proximal
inter-
phalangeal
joint
Wrist
plate
Steel
supporting
structure
NIRS
optodes
attached
to
forearm
(without
covering
cloth)
Set
square
B.
Point
of
set
square
placed
on
acromion
process
to
check
angle
of
upper
arm
30'
60'
Physiological
responses
to
a
climbing-specific
task
1435
A.
-
Adjustable
elbow
rest
Upper
arm
horizontally
adducted
60'
relative
to
shoulder
girdle
axis
Shoulder
girdle
of
participant
Acromion
process
Figure
1.
Test
apparatus.
(A)
Finger
testing
apparatus
and
arm
positioning.
(B)
Schematic
representation
of
positioning
of
the
participant
(transverse
plane).
Finger
force
plate
rock
face.
Force
produced
from
the
fingers
is
determined
by
the
extent
of
distortion
in
the
finger
plate.
The
plate
is
attached
to
a
strain
gauge
(581
DNH
Peekel,
Rotterdam,
Netherlands)
and
compu-
ter
via
a
strain
gauge
bridge,
amplifier,
and
analog-
to-digital
converter.
The
apparatus
was
calibrated
before
each
test
session.
During
the
endurance
tests,
the
participants
were
given
feedback
about
the
force
produced
and
the
timing
of
contractions
by
a
computer
monitor
and
audio
speakers.
Software
was
written
so
that
an
audio
cue
"load"
or
"rest"
was
given
when
the
contraction
time
began
or
ended.
"Traffic
lights"
and
a
bar
display
on
the
monitor
assisted
the
participants
to
maintain
the
correct
force,
showing
green
for
correct
force,
blue
for
excessive
force,
and
red
for
too
little
force.
The
fingers
of
the
right
hand
were
positioned
on
the
plate
ensuring
maximum
contact
with
the
plate
1436
D.
MacLeod
et
al.
surface.
The
amount
of
space
available
for
the
fingers
was
limited
by
a
metal
"stop"
on
the
plate
surface.
The
participants
were
instructed
to
use
an
"open
crimp"
position
(Goddard
&
Neumann,
1993)
with
the
fingers
flexed
at
the
proximal
inter-phalangeal
joint.
Chalk
(magnesium
carbonate)
was
used
to
promote
optimum
grip
on
the
plate.
The
thumb
was
not
allowed
to
make
contact
with
the
plate.
The
partici-
pant's
right
elbow
rested
on
an
adjustable
plate
to
minimize
the
contribution
of
the
proximal
arm,
shoulder,
and
back
muscles
in
pulling
during
the
tests.
The
participants
were
positioned
so
that
the
upper
arm
and
forearm
formed
a
90°
angle,
and
the
inferior
aspect
of
the
acromion
process
and
the
antecubital
fossa
were
level.
This
was
achieved
by
adjusting
the
height
of
the
apparatus
platform
as
described
in
Grant
et
al.
(2003).
The
upper
arm
was
adducted
horizontally
by
60°
relative
to
the
shoulder
girdle
(transverse
plane)
for
optimum
specificity
for
climb-
ing
and
comfort
(Quaine,
Martin,
&
Bianchi,
1997).
The
point
of
a
set
square
was
placed
on
the
acromion
process.
The
long
side
of
the
set
square
opposite
the
hypotenuse
was
set
parallel
with
the
base
of
the
force
plate
apparatus
at
right
angles
to
the
shoulder
girdle.
The
hypotenuse
edge
of
the
set
square
was
placed
horizontally
from
the
acromion
process
and
the
participant's
forearm
was
pushed
against
the
hypotenuse
edge
to
establish
the
desired
position
(Figure
1B).
Habituation
and
warm-up
Before
MVC
measurements
(visit
1),
the
participants
were
asked
to
perform
three
sub-maximal
contrac-
tions
of
5
s
each
on
the
plate
with
30
s
rest
between
contractions
and
2
min
rest
before
proceeding
to
MVC
measurement.
After
MVC
measurement,
the
participants
were
accustomed
to
the
endurance
test
protocol.
Habituation
test
A
consisted
of
two
contractions
at
40%
of
MVC
lasting
10
s,
with
1
min
rest
between
contractions.
Habituation
test
B
consisted
of
one
trial
of
six
contraction/relaxation
cycles
(10
s
contraction,
3
s
relaxation).
This
habi-
tuation
procedure
was
repeated
as
a
warm-up
at
visits
2
and
3.
Test
procedure
During
visit
1,
all
participants
performed
eight
MVC
attempts
with
1
min
rest
between
attempts.
Note
that
5
min
rest
was
allowed
after
the
third
and
sixth
attempts
to
prevent
accumulation
of
fatigue.
Strong
verbal
encouragement
was
given
to
all
participants
to
optimize
the
MVC
scores
(McNair,
Depledge,
Brettkelly,
&
Stanley,
1995).
If
the
final
attempt
produced
the
highest
score,
another
measurement
was
taken
to
ensure
a
representative
value
was
obtained.
On
visit
2,
the
participants
undertook
another
four
MVC
attempts
in
an
effort
to
ensure
the
maximum
value
attained
on
visit
1
was
representative
of
the
participant's
true
maximum.
Any
value
higher
than
that
recorded
in
the
first
visit
was
recorded
as
MVC.
The
participants
performed
the
two
endurance
tests
on
visits
2
and
3,
in
randomized
order.
The
endurance
contractions
were
performed
at
40%
of
MVC.
The
bar
on
the
monitor
display
flashed
red
when
the
force
fell
2.5%
below
this.
Each
test
was
ended
automatically
by
the
computer
when
the
bar
flashed
red
for
longer
than
1
s.
Verbal
encourage-
ment
was
provided
to
all
participants.
In
the
continuous
test,
the
participants
maintained
a
continuous
isometric
contraction
on
the
plate
at
40%
(s=
2.5%)
until
volitional
exhaustion.
In
the
intermittent
test,
the
participants
maintained
a
cycle
of
continuous
isometric
contractions
at
40%
(s
=
2.5%)
for
10
s,
followed
by
3-s
rest
periods
until
volitional
exhaustion.
This
test
was
designed
to
mimic
the
contraction/relaxation
peri-
ods
identified
by
Schadle-Schardt
(1998)
as
being
typical
contraction/relaxation
ratios
used
in
sport
climbing.
Anthropometry
Body
mass
was
measured
using
scales
(Avery
Beam
Balance,
Birmingham,
UK).
Stature
was
measured
using
a
stadiometer
(Holtain
Ltd,
Crymych,
UK).
Percentage
body
fat
was
predicted
by
taking
four
skinfold
measurements
(Holtain
skinfold
limiting
calliper)
using
the
method
of
Durnin
and
Womersly
(1974).
All
skinfold
measurements
were
taken
from
the
right
side
of
the
body
and
by
the
same
researcher.
Forearm
circumference
was
measured
to
the
nearest
0.5
cm
using
a
measuring
tape
(Dean,
London,
UK).
Measurements
were
taken
from
the
widest
point
of
the
forearm,
near
the
proximal
end.
Blood
pressure
Blood
pressure
measurements
were
taken
using
an
electronic
blood
pressure
cuff
(Colin
BP-88/BP-88C
Patient
Monitor),
positioned
on
the
participant's
left
(resting)
arm.
All
measurements
were
taken
with
the
participant
in
the
test
position
to
avoid
any
variations
due
to
body
position
(Webster,
Newham, Petrie,
&
Lovell,
1984).
Resting
blood
pressure
was
measured
three
times
at
1-min
intervals
after
3
min
of
quiet
rest.
The
third
measurement
was
used
as
the
resting
value.
The
blood
pressure
apparatus
varied
in
cycling
time
depending
on
the
participant's
blood
pressure
at
the
time
of
cuff
inflation.
If
the
participant's
blood
pressure
was
high,
the
cuff
took
longer
to
inflate.
The
machine
was
cycled
Physiological
responses
to
a
climbing-specific
task
1437
continuously
until
cessation
of
the
test.
The
last
value
obtained
during
the
test
was
used
in
the
analyses.
The
timing
of
measurement
of
this
value
varied
due
to
differences
in
blood
pressure
between
participants
and
length
of
the
test.
Near
infra-red
spectroscopy
Changes
in
muscle
blood
volume
and
oxygenation
were
recorded
in
the
flexor
digitorum
superficialis
of
the
test
forearm
using
near
infra-red
spectroscopy
(NIRS)
(NIRO-500
Hamamatsu
Photonics
K.K.,
Japan).
The
flexor
digitorum
superficialis
(FDS)
flexes
the
fingers
at
the
proximal
inter-phalangeal
joint
and
was
considered
the
most
suitable
muscle
in
which
to
monitor
haematological
changes
due
to
simulated
climbing.
The
NIRS
optodes
were
placed
4
cm
apart
on
the
anterior
forearm
surface,
over
the
belly
of
the
flexor
digitorum
superficialis.
The
flexor
digitorum
superficialis
was
located
by
palpation
and
correct
placement
of
the
optodes
was
confirmed
by
observing
the
selective
response
of
muscle
blood
oxygenation
and
volume
to
FDS
activation.
The
optodes
were
positioned
and
warmed
up
according
to
the
manufacturer's
instructions.
The
NIRO-500
measures
changes
in
muscle
blood
oxygenation
and
volume
in
the
portion
of
the
muscle
between
the
optodes
in
µAl
relative
to
the
resting
value
at
the
start
of
the
test.
Muscle
blood
oxygenation
and
volume
were
sampled
at
2
Hz
and
changes
in
chromophore
concentrations
were
calculated
using
software
(ON-
MAIN
Hamamatsu
Photonics).
All
participants
had
a
generally
low
percentage
body
fat
(mean
13%,
s
=
4).
Therefore,
we
assumed
that
subcutaneous
adipose
tissue
thickness
did
not
affect
the
penetration
of
the
infra-red
light.
Statistical
analysis
Differences
between
the
group
means
were
deter-
mined
using
two-sample
t-tests
with
statistical
significance
set
at
P
<
0.05.
Data
for
both
groups
of
participants
were
pooled
to
examine
physiological
responses
to
the
test
procedures.
The
software
used
was
Minitab
version
13
by
Minitab
Inc.,
PA,
USA.
Linear
regression
was
used
to
analyse
the
relation-
ship
of
these
responses
to
finger
endurance,
as
measured
by
the
force—time
integral
from
the
endurance
tests
(0.4
*
MVC
*
test
time).
The
force—time
integral
was
chosen
as
a
measure
of
"climbing-specific"
endurance
rather
than
test
time
alone,
as
it
combines
relevant
variables
and thus
provides
a
representative
value.
The
absolute
force
produced
by
the
finger
flexors
and
the
duration
of
the
climbing
bout
are
both
likely
to
affect
the
muscular
effort
expended.
If
the
participant
has
an
advantage
in
any
of
these
variables,
it
is
likely
that
endurance
capacity
will
be
increased.
Results
The
climbers
had
greater
absolute
MVC,
despite
having
a
lower
body
mass
(Table
I).
Linear
regression
revealed
a
relationship
between
MVC
and
climbing
performance
(climbing
grade).
MVC
explained
49.9%
of
the
variability
(r=
0.706)
in
the
climbers'
climbing
grade.
Group
mean
endurance
test
times
were
similar.
There
was
a
group
difference
in
force—
time
integral
in
the
intermittent
test
(P=0.001)
(Table
I).
Multiple
regression
revealed
no
relationship
between
the
climbers'
force
time
integral
(both
tests)
and
climbing
performance.
Blood
pressure
Group
mean
systolic
and
diastolic
blood
pressure
increased
during
the
endurance
tests
(pressor
re-
sponse)
(P=
0.001),
although
there
were
no
differ-
ences
in
group
mean
blood
pressure
responses
(Figure
2).
Linear
regression
was
used
to
analyse
the
relationship
of
pressor
response
and
the
force—
time
integral
for
both
tests
(pooled
data
from
both
Table
I.
Anthropometric
characteristics,
strength
and
endurance
scores
for
climbers
and
non-climbers
(mean±s).
Characteristic
Climbers
(n=11)
Non-climbers
(n=9)
95%
CI
for
difference
in
group
mean
Stature
(cm)
175.5+6.7
179.9+5.3
(-1.3,
10.1)
Body
mass
(kg)
66.4+6.8
75.5+6.3
(2.9,
15.3)*
Percentage
body
fat
11.3+3.6
14.9+3.0
(0.2,
7.0)*
Forearm
circumference
(cm)
27.8+1.0
27.6+1.6
(-1.5,
1.2)
Forearm
circumference
(cm
kg
-1
)
0.4+0.0
0.37±0.0
(0.1,
0.0)*
MVC
(N)
485+65
375+91
(187,
32)*
MVC/body
mass
(N
kg
-1
)
7.4+1.2
5.0+1.2
(3.6,
1.2)*
Intermittent
test
time
(s)
277.7+83.0
251.6+107.2
(-120.6,
68.4)
Continuous
test
time
(s)
110.5+28.1
105.3+29.4
(-33.9,
23.6)
Force—time
integral
(intermittent
test)
(N
s)
51,769+12,229
35,325+9724
(27,140,
5746)*
Force—time
integral
(continuous
test)
(N
s)
21,043+4474
15,816+6263
(10,876,
—423)
*
Significant
difference
between
group
means
(P
<
0.05).
200
180
-
cn
2
E
160
1438
D.
MacLeod
et
al.
-
-.--
Non-climbers
—.—
Climbers
E
o
140
-
Continuous
Test
Systolic
BP
Diastolic
BP
0
80
-
o
regression
was
used
to
analyse
the
relationship
be-
tween
finger
flexor
re-oxygenation
and
the
force—
time
integral.
There
was
a
significant
positive
relationship
between
rest
phase
re-oxygenation
and
the
force
—time
integral
(P=
0.005).
Rest
phase
re-
oxygenation
explained
41.1%
of
the
variability
in
the
force—time
integral.
Multiple
regression
was
used
to
analyse
the
relationship
between
pressor
response
(systolic
and
diastolic)
and
rest
phase
re-oxygenation.
No
relationships
were
observed.
Fa
60
-
40
Rest
End
200
Intermittent
Test
Systolic
BP
#
a
u)
120
co
P.
a
100
Diastolic
BP
o
o
80
03
60
40
Rest
End
Figure
2.
Group
mean
blood
pressure
responses
for
the
endurance
tests.
#
Significant
difference
from
rest.
- -
+;
-
-,
non-climbers;
—M—,
climbers.
groups,
n
=
20).
Both
systolic
and
diastolic
pressor
responses
were
not
related
to
the
force—time
integral
for
both
tests
(continuous
test
P=
0.700,
intermit-
tent
test
P=
0.451).
NIRS
analysis
(intermittent
test)
Muscle
blood
oxygenation
[HbO
2
]
tended
to
de-
crease
during
contractions
and
recover
(re-oxygena-
tion)
during
rest
phases,
creating
a
pattern
of
"peaks"
and
"troughs"
(Figure
3).
Re-oxygenation
(A
[HbO
2
])
during
the
3-s
rest
phases
was
repre-
sented
by
the
difference
between
[HbO
2
]
at
the
start
of
a
rest
phase
("trough")
and
that
at
the
end
of
a
rest
phase
("peak").
The
medians
of
the
first
three
rest
phases,
last
three
rest
phases,
and
middle
three
rest
phases
of
the
test
for
each
participant
were
selected
for
analysis
because
they
gave
a
representative
profile
of
[HbO
2
]
changes
during
the
test.
Due
to
the
variable
test
times between
participants,
the
values
represent
relative
rather
than
absolute
time
points.
Rest
phase
re-oxygenation
was
significantly
greater
in
climbers
than
in
non-
climbers
at
the
middle
of
the
test
(P=
0.001)
and
end
of
the
test
(P=
0.001)
(Figure
4).
Multiple
NIRS
analysis
(continuous
test)
Analysis
of
group
mean
change
in
muscle
blood
volume
(A
[HbT])
and
A
[HbO
2
]
was
performed
at
20%
incremental
time
points
from
0%
(test
start)
to
100%
(end
point
of
the
test).
Change
in
muscle
blood
volume
increased
relative
to
rest
in
non-
climbers
at
the
40%
to
100%
time
points
(P=
0.001),
but
only
at
100%
in
climbers
(P=
0.001).
A[HbT]
increased
significantly
relative
to
rest
in
non-climbers
at
40%
—100%
time
points
(P
values
<
0.05),
but
only
at
100%
in
climbers
(P=
0.045).
A[HbT]
was
significantly
greater
in
non-climbers
than
climbers
at
40%
(P=
0.023)
and
60%
time
points
(P=
0.014)
(Figure
5).
A[HbO
2
]
decreased
relative
to
rest
and
the
change
was
greater
in
the
climbers
than
in
non-climbers,
although
P
values
<
0.05
at
all
points
in
the
test,
for
both
groups
(Figure
5).
Multiple
regression
revealed
no
relationship
between
A[HbT]
or
A
[HbO
2
]
and
the
force
time
integral.
Discussion
Climbing-specific
endurance
There
were
no
differences
between
groups
for
endurance
test
times
(Table
1).
This
finding
is
surprising,
as
Carlson
and
McGraw
(1971)
observed
lower
isometric
endurance
in
individuals
with
higher
MVC.
Based
on
these
findings,
it
might
be
antici-
pated
that
the
climbers
in
the
present
study
would
have
shorter
endurance
times
as
they
had
much
higher
MVCs
than
the
non-climbers.
Both
groups
exerted
force
at
40%
MVC
but
the
absolute
force
of
the
climbers
was
greater.
Carlson
(1969)
and
Carlson
and
McGraw
(1971)
hypothesized
that
a
negative
relationship
between
MVC
and
isometric
endurance
can
be
explained
by
the
fact
that
blood
flow
is
progressively
occluded
as
force
increases.
Thus,
in
a
group
with
a
higher
absolute
force,
there
would
be
greater
blood
flow
occlusion
and
a
reduced
endurance
time.
The
results
from
the
present
study
differ
from
the
findings
of
Ferguson
and
Brown
(1997),
who
observed
greater
intermittent
isometric
forearm
endurance
times
in
a
trained
climbing
......
180
a)
1
160
-
E
E
140
2
--4--
Non-climbers
Climbers
Physiological
responses
to
a
climbing-specific
task
1439
t
i
451
501
r
v\A
30
-
20
Intermittent
Test
10
0
51
101
151
201
251
301 351
401
-
10
-20
-
30
-
-40
-
50
-
20
10
Continuous
Test
50
1
00
15
0
-
10
-
20
-
30
-40
-
I
Figure
3.
Example
of
NIRS
traces
of
changes
in
muscle
blood
oxygenation
[HbO
2
]
during
the
endurance
tests
showing
changes
in
AM
relative
to
rest
(set
to
zero
before
the
start
of
the
test).
Black
trace
=
climber,
white
trace
=
non
climber.
y-axis
=
[HbO
2
]
AM
(zero
=
resting
value),
x-axis
=
time
(s).
"0"
denotes
the
start
of
the
test.
Exercise
ceased
at
501
s
into
the
intermittent
test,
and
at
154
s
into
the
continuous
test.
Mean
c
hang
e
in
[
HbO2]
dur
ing
res
t
p
hase
(u
M)
35
30
25
20
15
10
5
Start
Mid-point
End
Figure
4.
Group
mean
rest
phase
re-oxygenation
during
the
intermittent
test.
The
values
represent
the
difference
between
[HbO
2
]
at
the
start
of
a
rest
phase
("trough")
and
end
of
a
rest
phase
("peak").
Start
=
median
of
A[HbO
2
]
during
first
three
rest
phases
of
the
test.
Mid-point=
median
of
middle
three
phases
of
the
test.
End
=
median
of
final
three
rest
phases
of
test.
*
Significant
difference
between
group
means
(P
<
0.05).
-
-
-
non-climbers;
—M—,
climbers.
group.
Ferguson
and
Brown
also
used
contractions
of
40%
MVC
but
observed
similar
absolute
forces
between
a
group
of
trained
climbers
and
non-
climbing
controls.
The
absence
of
group
differences
in
MVC
observed
by
Ferguson
and
Brown
might
have
been
attributable
to
the
climbing
specificity
of
the
test
apparatus.
The
superior
endurance
times
of
climbers
observed
by
Ferguson
and
Brown
could
be
related
both
to
the
absence
of
group
MVC
differ-
ences
and
greater
vasodilatory
capacity
in
the
climbers.
We
hypothesized
that,
in
the
present
study,
any
endurance
disadvantage
due
to
superior
MVC
in
the
climbers
is
offset
by
the
increased
vasodilatory
capacity
possessed
by
the
participants.
The
inter-
mittent
test
in
the
present
study
was
designed
to
simulate
closely
the
contraction
patterns
experienced
during
climbing.
Ferguson
and
Brown
(1997)
used
a
contraction—relaxation
ratio
of
5
s
to
2
s,
and
measured
endurance
times
to
fatigue
of
over
12
min
in
climbers.
The
test
times
for
the
climbers
in
the
present
study
were
generally
between
4
and
5
min,
similar
to
the
times
measured
for
completion
of
World
Cup
competition
routes
(Schadle-Schardt,
1998).
It
is
therefore
conceivable
that
40% MVC
is
representative
of
the
forces
required
at
the
fingers
in
real
climbing.
However,
more
research
is
required
to
obtain
direct
evidence
of
the
forces
generated
in
the
fingers,
as
well
as
realistic
contraction—relaxation
ratios
during
different
sport
climbing
types
(indoor
competitions,
outdoor
rock
climbs).
*
---
--.--
Non-climbers
Climbers
5
-5
-
-10
-
-15
-
Fj
-20
-
_
-25
-
-30
-
-
35
-
-40
-
-45
35
25
-
*
15
-
5
I
-5
-
15
-
25
End
20
40
60
80
Start
1440
D.
MacLeod
et
al.
Start
20
40
60
80
End
Time
point
of
test
(%)
Time
point
of
test
(%)
Figure
5.
Group
mean
changes
in
NIRS
variables
during
the
continuous
test
(HbO2,
HbT)
(µM)
relative
to
resting
value
(rest
=
zero).
*
Significant
difference
between
group
means
(P
<
0.05).
#
Significant
difference
from
rest
(P
<
0.05).
-
-
-
-,
non-
climbers;
—,
climbers.
To
make
useful
comparisons
between
the
groups
for
climbing-specific
endurance,
absolute
force
and
en-
durance
time
were
combined
to
provide
a
relevant
measure
of
the
muscular
effort
performed
in
the
test
(the
force
—time
integral).
There
was
a
group
differ-
ence
in
force-time
integral,
intermittent
test:
(P=
0.001).
That
this
advantage
reached
significance
only
in
the
climbing-specific
(intermittent)
endurance
test
underlines
the
unique
physiological
demands
of
this
activity.
We
conclude
that
climbing-specific
endurance
is
an
important
characteristic
of
trained
climbers.
However,
we
observed
no
relationship
in
the
intermittent
or
the
continuous
test
between
the
force—
time
integral
and
climbing
grade.
The
lack
of
strength
in
this
relationship,
despite
the
large
differences
in
the
force
—time
integral
between
groups,
might
be
ex-
plained
by
the
small
sample
in
the
climbing
group
(n=
11)
and
narrow
variation
of
climbing
ability
among
the
participants.
It
should
also
be
recognized
that
endurance
is
only
one
of
several
factors
that
might
contribute,
to
varying
extents,
to
success
in
rock
climbing.
Other
factors
that
influence
performance
include
route-finding
skills,
movement
ability,
finger
strength
and
strength
in
several
body
areas,
flexibility,
and
psychological
factors.
Determinants
of
the
force
time
integral
Both
systolic
and
diastolic
blood
pressure
rose
during
the
endurance
tests,
as
anticipated
for
isometric
exercise
(Jones
&
Round,
1990).
Increasing
central
arterial
blood
pressure
has
been
shown
to
enhance
force
production
during
isometric
muscle
activity
(Wright
et
al.,
2000).
It
was
hypothesized
that
an
increased
pressor
response
would
confer
a
perfor-
mance
advantage
in
the
endurance
tests
by
opposing
occlusion
caused
by
the
muscular
activity
and thus
permit
increased
intramuscular
blood
flow.
There
were
no
group
differences
in
pressor
response
(Continuous
test:
P=
0.207
systolic,
P=
0.857
dias-
tolic.
Intermittent
test:
P=
0.326
systolic,
P=
0.172
diastolic).
As
there
were
no
relationships
between
pressor
response
and
the
force—time
integral,
it
is
suggested
from
these
data
that
an
increased
pressor
response
does
not
confer
an
advantage
in
climbing-
specific
endurance.
Wright
et
al.
(2000)
also
demon-
strated
that
the
positive
effect
on
abductor
pollicis
force
production
from
increasing
blood
pressure
could
be
removed
by
elevating
the
hand.
It
is
plausible
that
a
similar
effect
could
have
occurred
in
the
present
study,
and
could
also
occur
in
climbing
(where
the
arms
are
often
extended
above
the
head).
Several
studies
have
observed
that
training
with
fatiguing
ischaemic
muscle
actions
results
in
at-
tenuation
of
the
pressor
response.
Such
adaptations
are
thought
to
be
due
to
changes
in
the
sensitivity
of
the
peripheral
chemoreceptors
and
mechanorecep-
tors
and
the
central
command
component
of
the
cardiovascular
response.
Ferguson
and
Brown
(1997)
observed
an
attenuated
blood
pressure
response
in
trained
climbers
during
isometric
hand-grip
exercise
compared
with
non-climbers.
The
magnitude
of
the
pressor
response
varies
with
exercise
intensity
and
duration
(Kahn,
Favriou,
Jouanin,
&
Grucza,
2000).
The
pressor
response
to
isometric
exercise
is
affected
by
a
central
command
component
(MacDougall
et
al.,
1992)
related
to
the
effort
produced
by
the
individual,
and
by
a
peripheral
component
related
to
the
build
up
of
metabolites
in
the
exercising
muscle
and
to
muscle
mechanoreceptors.
Considerable
verbal
encourage-
ment
was
given
to
all
participants
to
ensure
maximum
effort.
However,
it
is
plausible
that
the
climbers,
being
more
accustomed
to
producing
maximum
efforts
of
a
similar
type,
were
able
to
produce
a
greater
effort
and thus
exhibit
a
larger
central
command-mediated
pressor
response.
Furthermore,
the
higher
forces
produced
by
the
climbers
(due
to
the
higher
MVC)
could
have
accounted
for
the
trend
for
a
large
pressor
response
Physiological
responses
to
a
climbing-specific
task
1441
in
the
climbers,
via
a
peripheral
response
to
greater
activation
of
chemoreceptors
and
mechanoreceptors
within
the
exercising
muscles.
The
larger
change
in
forearm
oxygenation
in
climbers
during
the
endur-
ance
tests
supports
the
hypothesis
that
a
larger
metaboreflex
could
have
occurred.
The
larger
forces
produced
by
the
climbers
compared
with
the
non-
climbers
in
the
present
study
could
account
for
the
contrast
with
the
findings
of
Ferguson
and
Brown
(1997),
as
the
forces
produced
in
that
study
were
similar
between
climbers
and
non-climbers.
Near
infra-red
spectroscopy
After
completing
the
endurance
tests,
the
participants
commented
on
having
a
painful
burning
"pump"
in
the
forearm
muscles
and
the
forearm
was
visibly
larger
and
firm
to
the
touch.
This
is
consistent
with
the
type
of
forearm
fatigue
experienced
in
rock
climbing
(Goddard
&
Neumann,
1993).
During
the
intermittent
test,
MRS-determined
muscle
blood
oxygenation
[HbO
2
]
fell
rapidly
from
the
resting
value
and
followed
a
pattern
of
"peaks"
and
"troughs",
corresponding
to
the
relaxations
and
contractions
respectively
(Figure
3).
We
hypothesized
that
the
ability
to
restore
muscle
oxygenation
during
the
rest
phases
would
be
an
important
predictor
of
climbing-
specific
endurance
performance.
There
were
reoxy-
genation
group
differences
(P=
0.001)
at
the
middle
and
end
of
the
test
(Figure
4).
There
was
a
positive
relationship
between
rest
phase
A
[Hb0
2
]
and
climbing-specific
endurance
(force
—time
integral)
(R
2
=
41.1%).
Thus
we
conclude
from
these
results
that
muscle
re-oxygenation
during
rest
phases
is
an
important
determinant
of
climbing-specific
endurance.
We
hypothesized
that
forearm
re-oxygenation
during
the
rest
phases
would
be
directly
related
to
the
magnitude
of
the
pressor
response,
via
an
opposition
of
the
mechanical
vasoconstriction
caused
by
high
intramuscular
pressure
(Asmussen,
1981).
Although
there
was
a
weak
positive
relationship,
it
was
not
significant
(P=
0.273
and
P=
0.162
at
50%
and
100%
time
points
respectively).
Thus,
we
conclude
from
these
results
that
forearm
oxygenation
is
not
dependent
on
the
pressor
response
in
a
climbing-specific
endur-
ance
test.
Factors
influencing
forearm
re-oxygenation
during
rest
phases
could
include
muscle
capillary
density,
vasodilatory
capacity
(Ferguson
&
Brown,
1997),
and
muscle
fibre
relaxation
times
(Jones
&
Round,
1990).
Training
regimes
promoting
angiogen-
esis
in
the
forearm
muscles
could
be
an
important
component
of
training
for
elite
rock
climbing.
In
the
continuous
test,
the
change
in
muscle
blood
volume
was
greater
in
the
non-climbers
than
the
climbers
at
various
time
points
during
the
test
(P=
0.023-40%,
P=
0.014-60%).
Figure
5
sug-
gests
greater
occlusion
of
blood
flow
during
contrac-
tions
at
40% MVC
in
the
climbers.
This
could
be
explained
by
the
higher
absolute
forces
exerted
by
the
climbers.
The
greater
occlusion
points
to
improved
muscle
fibre
recruitment
during
contrac-
tion
in
trained
rock
climbers,
rather
than
greater
muscle
mass
in
the
forearms
alone.
This
speculation
is
supported
by
the
absence
of
differences
in
absolute
forearm
circumference
between
the
groups.
How-
ever,
when
forearm
circumference
is
corrected
for
body
mass,
the
forearm
circumference
of
the
climbers
was
greater
(P=
0.001)
(Table
I).
Similar
endurance
tests
performed
across
a
range
of
percen-
tages
of
MVC
could
yield
further
information
about
the
extent
of
blood
flow
occlusion
during
climbing-
specific
contractions
of
different
intensities.
Finger
strength
(MVC)
The
climbers
had
greater
finger
strength
than
the
non-climbers
using
a
climbing-specific
protocol
(P=
0.009)
(Table
I).
This
was
despite
the
fact
that
the
non-climbers
had
a
higher
mean
body
mass.
These
results
agree
with
previous
studies
that
have
suggested
that
climbers
have
stronger
fingers
than
non-climbers
(Bollen
&
Cutts,
1993;
Grant
et
al.,
1996).
However,
these
authors
did
not
report
the
large
differences
in
MVC
scores
between
the
climbers
and
non-climbers
seen
in
the
present
study.
The
smaller
differences
between
the
climbers
and
non-climbers
observed
by
Grant
et
al.
(1996)
might
be
attributable
to
the
relatively
low
climbing
standard
of
the
"elite"
group.
The
results
of
the
present
study
confirm
that
climbers
possess
greater
finger
strength
than
non-climbers,
particularly
when
a
climbing-
specific
test
protocol
is
used
with
a
highly
trained
group
of
individuals.
There
was
a
positive
relation-
ship
between
climbing
ability
(measured
by
on-sight
grade)
and
MVC,
explaining
49.9%
of
the
variability
in
climbing
grade
in
the
climbers.
This
finding
suggests
that
increased
finger
strength
confers
a
performance
advantage
in
rock
climbing.
This
result
is
perhaps
surprising
given
that
sport
climbing
has
an
endurance
component,
as
the
overall
exercise
duration
is
likely
to
last
for
more
than
4
min
(Schadle-Schardt,
1998).
However,
given
that
the
finger
flexors
(a
small
muscle
group)
must
contract
isometrically
and
support
large
proportions
of
body
weight,
and
that
complete
occlusion
of
blood
flow
occurs
at
45
75%
of
MVC
in
isometric
exercise
(Barnes,
1980;
Heyward,
1980;
Serfass,
Stull,
Ben
Sera,
&
Kearney,
1979),
it
is
likely
that
there
is
marked
occlusion
of
blood
flow
to
the
exercising
muscles
during
many
of
the
moves
on
a
climbing
route.
Indeed,
NIRS
data
from
the
present
study
suggest
such
occlusion
(Figure
5)
and
de-oxygenation
(Figures
3,
5)
is
greater
during
contractions
in
climbers,
despite
their
superior
endurance
capacity
1442
D.
MacLeod
et
al.
(force
—time
integral)
(P=
0.001).
The
isometric
contractions
made
during
moves
are
interrupted
by
short
periods
of
rest
while
reaching
to
the
next
hold.
Near
infra-red
spectroscopy-determined
forearm
[HbO
2
]
showed
considerable
recovery
towards
rest-
ing
values
during
these
rest
periods
(Figure
3),
even
as
the
participants
approached
the
point
of
failure
in
the
test.
It
is
possible
that
finger
strength
character-
istics
—specifically
coordination
and
fine
control
of
force
production—could
frequently
be
the
direct
causative
factor
for
failure
(falls),
rather
than
muscle
fatigue
itself.
Even
long-endurance
rock
climbs
can
have
forceful
individual
movements
where
large
forces,
muscular
fine
control,
and
coordination
are
required
for
success.
Twitch
relaxation
time
tends
to
become
slowed
during
isometric
fatigue,
affecting
the
frequency
at
which
tetanic
fusion
occurs.
A
slowing
of
motor
unit
firing
rate
occurs
as
a
reflex
response
to
the
change
in
relaxation
time
(Bigland-
Ritchie,
Dawson,
Johansson,
&
Lippold,
1986),
the
purpose
of
which
is
to
maintain
muscular
fine
control
(Spurway,
1999).
Falls
could
be
caused
by
loss
of
fine
control
and
coordination
where
firing
frequencies
are
high.
Greater
isometric
strength
would
reduce
the
requirement
for
high
firing
frequencies
for
a
given
climbing
movement.
Anthropometry
An
attempt
was
made
to
recruit
individuals
of
similar
age,
stature,
and
physical
build
for
compar-
ison
of
absolute
forces
recorded
for
strength
and
endurance.
There
were
no
significant
differences
between
groups
for
age
(P=
0.144)
and
stature
(P=
0.119)
(Table
I).
However,
it
was
not
possible
to
recruit
sufficient
individuals
of
similar
body
mass.
The
climbers
had
lower
body
mass
and
percentage
body
fat
than
the
non-climbers.
These
results
support
the
findings
of
Watts
and
colleagues
(Watts,
Daggett,
Gallagher,
&
Wilkins,
2000;
Watts,
Martin,
&
Durtschi,
1993;
Watts
et
al.,
1996)
that
trained
rock
climbers
tend
to
have
a
lower
body
mass
and
percentage
body
fat.
It
is
feasible
that
a
large
body
mass
or
any
excess
body
fat
would
be
disadvantageous
in
elite
climbing
as
body
weight
must
be
moved
repeatedly
against
gravity.
However,
it
is
well
known
that
climbers
have
long
considered
excess
body
fat
to
be
a
disadvantage
and
many
climbers
attempt
to
control
it
strictly.
It
is
also
considered
advantageous
to
avoid
hypertrophy
training
of
lower-body
muscle
groups.
Hence,
the
question
remains
whether
body
mass
and
percentage
body
fat
are
important
determinants
of
climbing
performance
or
merely
features
of
climbers'
training
patterns
(Farrington,
1999).
It
is
conceivable
that
any
performance
advantage
conferred
by
maintaining
low
body
fat
could
be
offset
by
an
inadequate
energy
intake
to
support
a
rigorous
training
regime.
We
hypothe-
sizsed
that
climbers
would
possess
a
greater
muscle
mass
in
the
forearm
due
to
the
requirement
for
repeated
contractions
of
the
finger
flexors
and
other
forearm
muscles
in
climbing
movements.
There
were
no
differences
between
the
groups
in
absolute
forearm
circumference
(P=
0.817),
but
when
re-
lated
to
body
mass
the
climbers'
forearm
circum-
ference
was
significantly
greater
(P=
0.001)
(Table
I).
The
absence
of
marked
differences
in
the
absolute
values
could
be
explained
by
the
difference
in
body
mass
between
the
climbers
and
non-
climbers.
This
finding
is
in
line
with
that
of
Watts,
Joubert,
Lish,
Mast,
and
Wilkins
(2003),
who
observed
similar
forearm
volumes
in
competitive
climbers
and
controls,
despite
the
climbers'
lower
stature
and
body
mass.
Summary
Finger
endurance,
measured
as
the
force—time
integral,
was
greater
for
the
climbers
in
the
inter-
mittent
endurance
test
(P=
0.001).
Pressor
re-
sponses
were
similar
between
groups
and
not
related
to
the
force
—time
integral
for
either
test.
There
was
a
positive
relationship
between
change
in
muscle
blood
oxygenation
during
rest
phases
and
the
force
time
integral
(R
2
=
41.1%)
in
the
intermittent
test
(P=
0
.005)
.
Thus
we
conclude
from
our
results
that
muscle
re-oxygenation
during
rest
phases
is
a
good
predictor
of
endurance
performance.
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