Saddleback Journal of Biology - Saddleback College

Fall 2009 Biology 3B Paper
Results
The mean unmounted blood lactate
level at the walk was 0.0005 ± 1.13 x 10 -04
mM•L -1 •kg -1 (±SEM, N=5), at the trot was
0.0004 ± 8.9941 x10 -05 mM•L -1 •kg -1 (±SEM,
N=5), and at the canter was 0.0008 ± 9.853 x 10 -
05
mM•L -1 •kg -1 (±SEM, N=5). The mounted
blood lactate level at the walk was 0.0003 ± 4.17
x 10 -05 mM•L -1 •kg -1 (±SEM, N=5), at the trot
was 0.0003 ± 2.1 x10 -05 mM•L -1 •kg -1 (±SEM,
N=5), and at the canter was 0.0005 ± 8.25 x 10 -05
mM•L -1 •kg -1 (±SEM, N=5). As seen in Figure 1,
between the groups, no difference was found
when comparing mounted and unmounted values
in the walk and trot (p = 0.164 and p = 0.348
respectively). In the canter group a difference
was found (p = 0.026). Within the groups, a
difference was found between the unmounted
values for trot and canter (p = 0.007), and the
values for walk and canter (p = 0.044). Similarly
there was a difference found between the
mounted values for trot and canter (p = 0.006)
and walk and canter (p = 0.028).
Blood lactate (mM • L-1 • kg-1)
0.001
0.0009
0.0008
0.0007
0.0006
0.0005
0.0004
0.0003
0.0002
0.0001
0
Walk Trot Canter
Figure 1. Mean combined lactate levels at walk,
trot and canter unmounted versus mounted. No
difference was found between unmounted and
mounted blood lactate levels in the walk and trot
groups. A difference was found between
unmounted and mounted blood lactate levels in
the canter group (p = 0.026, Tukey Correction).
Discussion
Lactic acid is capable of releasing
energy to re-synthesize adenosine triphosphate
(ATP) without the involvement of oxygen.
Lactic acid is produced from pyruvate in the
glycolysis cycle via the enzyme lactate
dehydrogenase (LDH) during normal
metabolism and exercise. The amount of lactate
present after exercise can be a helpful tool in
determining performance because it is an
estimation of aerobic capacity (Poso, 2002).
Within the unmounted group, no
difference was found between the walk and the
trot values. However, the trot to canter and walk
to canter comparisons showed a significant
difference in blood lactate values. Similarly
within the mounted group the walk to trot
comparison revealed no difference, where the
trot to canter and walk to canter assessments
discovered a significant difference.
The hypothesis for this project stated
that blood lactate levels would be higher at all
three gaits while mounted versus unmounted.
However, collected data showed that blood
lactate levels were higher in the unmounted
group. No statistical difference was found when
comparing the mounted and unmounted levels in
both the walk and the trot. This is most likely
because the animals were not pushed into a state
of anaerobic respiration at these gaits. For this
same reason, there was a difference found in the
canter values between the groups. Though there
are several variables that can be taken into
account when examining blood lactate levels, the
researchers believe that the results in this
experiment could be explained by looking at the
level of energy applied when comparing exercise
by lunging versus riding. During the unmounted
testing, horses showed a higher energy exertion
at the trot and canter when compared to the
mounted testing. This is evidenced by the
amount of forward momentum at each gait while
lunging versus under saddle.
Though this experiment did find a
significant difference, the relationship between
blood lactate production and increase in load was
opposite to what was originally hypothesized. In
a study to determine lactate minimum speed
(LMS), the individual lactate production and
removal rates, in horses, Gondim et al. (2007)
found no difference in blood lactate
concentration at rest and at LMS, despite an
increase in heart rate. The data found in both
these studies is inconsistent with the majority of
information available on blood lactate. LMS has
previously been tested in basketball players and
runners (Tegtbur et al., 1993), in swimmers
(Ribeiro et al., 2003) and rats (Voltarelli et al.,
2002) as well. In all the above studies lactate
levels at LMS were significantly higher than
those at rest (Gondim et al., 2007).
All of the above experiments indicate
that there exist one or more key differences in
the processing of post-exercise lactate in humans
and equines. There are several factors that can
affect the lactate concentration in blood and
these need to be accounted for when blood
114
Saddleback Journal of Biology
Spring 2010