The physiological and molecular response to repeated sprints in male and female team-sport athletes : a thesis presented in partial fulfillment of the requirements for the degree of Master of Science in Sport and Exercise Science at Massey University, Palmerston North, New Zealand
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Date
2009
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Massey University
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Abstract
Background: Due to the unique demands of the sport, athletes playing football perform a
variety of differing training methods to improve physiological performance. These include
strength, endurance and sprint training. While the effects of strength and endurance training
have been well researched, the effects of repeated-sprint training on blood and muscle
variables in well trained males and females are not well known. An understanding of
changes to the blood and muscle during and following an exercise bout are important, so to
gain an understanding of the type of stress and resulting adaptations that may occur. Also,
while a large volume of research in training adaptations has been performed on males; little
has been done on females. To date, some research indicates metabolism during moderateintensity
exercise may differ between males and females; however, no study has compared
repeated-sprint exercise. Therefore, it is unclear as to whether males and females would
have a differing physiological response to repeated-sprint training.
Purpose: The purpose of this study was to determine the effects of a repeated-sprint bout
on molecular signalling in muscle and blood measures and heart rate in well-trained
footballers. Additionally, we compared running times and sprint decrement (%).
Research Design: Eight female senior University football players (Mean ± SD, age, 19 ± 1
y, VO ?
2peak 53.0 ± 5.1 ml·kg-1min-1) and seven male senior University football players
(Mean ± SD, age, 19 ± 3 y, VO ?
2peak 59.0 ± 6.6 ml·kg-1min-1) volunteered to participate in
this study. Participants performed four bouts of 6 x 30 m maximal sprints spread equally
over a 40 min period. Sprint time was measured (at 30 m) for each sprint and sprint
decrement was also calculated for all bouts. Muscle biopsies were taken from the vastus
lateralis muscle at rest, 15 min following exercise and 2 h into recovery. Venous blood
samples were taken at the same time points as the biopsies while capillary blood lactate was
measured at rest and 3 min following each sprint bout. Repeated measures ANOVA and
Post hoc t-tests were performed to determine significant differences between the two groups
(male vs. female) and time points.
Findings: Both groups had a significant (P<0.05) increase in blood lactate (mM) after the
first bout of repeated sprints, with no differences between females (pre 0.9 ± 0.4 mM – post
10.0 ± 1.6 mM) and males (pre 0.8 ± 0.3 mM – post 10.0 ± 3.5 mM). Blood lactate
remained elevated compared to rest (P<0.05) following bouts 2, 3 and 4 for both females
(12.0 ± 3.6, 12.0 ± 3.3, 12.2 ± 3.8 mM respectively) and males (11.9 ± 2.9, 11.6 ± 2.3, 11.5
± 4.0 mM respectively), with no differences between groups or time points (P>0.05). There
were no differences (P>0.05) between the female and male athletes in mean heart rate
attained at the end of each bout of repeated sprints (187 ± 2 v 190 ± 2 bpm respectively) or
during recovery between sprints (140 ± 2 v 130 ± 2 bpm respectively). There were no
differences between groups or time points in blood insulin (P>0.05). Fastest 30 m sprint
time and mean 30 m sprint time during the repeated-sprint bout was faster for the males
than females (4.58 ± 0.12 v 5.26 ± 0.27 s respectively; (P>0.05)). However, there were no
differences in running velocity during the sprints between the males and females (165 ± 0.4
% vs. 155 ± 0.05 %; P>0.05) when expressed relative to velocity at VO ?
2peak (vVO ?
2peak).
Also, mean % decrement during the repeated-sprint bout was lower in the males then
females (4.9 ± 1.3 v 7.1 ± 1.9 % respectively; P<0.05). No changes were observed in total
or phosphorylated Akt at any time-point or between genders. However, while total 4E-BP1
was lower, the ratio of total to phosphoryalated 4E-BP1 at rest was greater in males than
females (P<0.05). Finally, there was also a significant decrease in 4E-BP1 phosphorylation
post-exercise in males (P<0.05), but not females.
Conclusions: There were no sex differences in blood lactate or heart rate throughout the
repeated-sprint bout. These findings suggest that there were no cardio respiratory or lactate
production/clearance differences in the response to a repeated-sprint-training bout between
sexes. However, while males were faster than their female counterparts, the average relative
speed was similar between sexes, suggesting a similar relative volume of work was
performed during the sprint bouts. However, the females did have a greater decrement in
sprint performance indicating a greater ability to recover sprint performance in the males.
Sex differences in resting total and phosphorylated 4E-BP1 may indicate greater potential
for muscle growth in the male athletes during basal conditions. However, differences could
be due to factors other than sex, including previous training history. There was a lack of
change in plasma insulin or Akt, but, similar to resistance exercise, a significant decrease in
post-exercise 4E-BP1 phosphorylation for the males, but not females. The sex differences in
the 4E-BP1 phosphorylation response post-exercise could be due to differences in the
metabolic disturbance in the muscle during and following maximal sprints.
Keywords: blood lactate, heart rate, muscle
Description
Keywords
Sprint training, Footballers, Physiological effects