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Sprinting

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Sprinting
Chapter 41
Sprinting
CERI W. NICHOLAS
Introduction
Of all sports, sprinting is the simplest. All that is
required to run the race is a start and finish line,
and an accepted method of starting the race. The
winner is the first person to cross the finish line.
Sprinting over short distances is one of man’s
earliest athletic pursuits. The pioneering event
in the ancient Olympic Games was the ‘stade’,
which was equivalent to the length of the
stadium — 192 m — at Atlis, the theatre of the
games (Quercetani 1964). Later, a second race,
the diaulos, equivalent to two stades (384 m), was
included as a foot race (Durant 1961).
The earliest records of the Olympic Games
credit the winner of the sprint event in the
ancient Olympics of 776 bc at Olympia to Coreobus, a cook from the nearby city of Elis. The
ancient tradition of honouring the fastest person
on the day still holds today in major championships, with the awarding of medals. The introduction of accurate and reliable time-keeping has
also led to the establishment of world records.
This has allowed athletes to compete against the
clock on tracks around the world and far from
the record holder (current world sprint records
are shown in Table 41.1).
In comparison with the encyclopaedic literature on endurance running, there is little information on sprinting. ‘Sprinting’ is also a generic
term used to describe brief maximum effort
during a wide range of activities, including
running, cycling, swimming, canoeing, rowing,
field hockey, soccer and rugby. Under these cir-
cumstances, the duration of the activity is often
different from track sprinting. Therefore, for the
purpose of this chapter, sprinting is considered
as brief maximal exercise, of less than 60 s duration. The intensity of exercise is well in excess of
that required to elicit maximum oxygen uptake
.
(Vo2max.), and there is no distribution of effort.
Setting aside the influence of natural talent
and appropriate training, correct nutrition
during training and competition is one of the
most important components in the formula for
success in sprinting. Athletes are notoriously
vulnerable to advertisements for nutritional supplements which make claims about enhancing
performance. Before reviewing the pertinent literature on nutrition and sprinting, this chapter
will provide a brief overview of physiological
and metabolic responses to sprinting, and the
onset of fatigue, both on the track and in the laboratory, and adaptations to sprint training.
Metabolic responses to sprinting
Only a few studies have examined the metabolic
responses to 100-m and 400-m track sprinting
(Hirvonen et al. 1987, 1992; Lacour et al. 1990;
Hautier et al. 1994; Locatelli & Arsac 1995).
Hirvonen et al. (1987) measured the muscle
adenosine triphosphate (ATP), phosphocreatine
(PCr) and lactate concentrations in seven male
sprinters before and after running 40, 60, 80 and
100 m at maximum speed. The fastest sprinters
utilized the greatest amount of PCr in the first 40,
60 and 80 m of the run (Fig. 41.2). Most of the PCr
535
536
sport-specific nutrition
Table 41.1 Current world sprint records (as at January 1999).
Distance (m)
Time (s)
Women
Sprinter
Time (s)
Sprinter
D. Bailey
10.49
F. Griffith-Joiner
9.84
200
19.32
M. Johnson
21.34
F. Griffith-Joiner
400
43.29
H. Reynolds
47.6
M. Koch
Phosphocreatine (mmol.kg–1 wt)
100
50
10
40
7.5
30
5.0
20
2.5
10
0
20
40
60
80
100
Speed (m.s–1)
Men
0
120
Distance (m)
Fig. 41.2 Speed (䊊) and muscle phosphocreatine
concentration (䊐) during a simulated 100-m track
sprint (Hirvonen et al. 1987).
Fig. 41.1 Sprinters and hurdlers in training complete
prolonged sessions with many short efforts, even
though competitions may involve only a single sprint.
Photo courtesy of Ron Maughan.
was used during the first 5–6 s of the race. The
decrease in running speed over the 100 m commenced when the high-energy phosphate stores
were markedly reduced and glycolysis was the
predominant energy provider. Lactate did not
accumulate to a level which could have inhibited
glycolysis and is unlikely to have been the principal cause of fatigue. These results show that the
rate of PCr utilization is critical to running speed.
In agreement with these results, Locatelli and
Arsac (1995) showed that anaerobic glycolysis
provided approximately 65–70% of the metabolic energy production during a 100-m race in
their study of four male and four female national
sprinters analysed during the 1994 Italian
championships.
The validity of postexercise lactate concentration as an indicator of the rate of anaerobic glycolysis was investigated in 400-m sprinting by
Lacour et al. (1990), and in 100-m and 200-m
sprinting by Hautier et al. (1994). In the study by
Lacour et al. (1990), blood samples were taken
sprinting
from 17 top level athletes within 10 min of completing a 400-m race in a major competition.
Postrace blood lactate concentrations were
highest in the fastest athletes, as reflected in the
strong correlation between running speed and
lactate concentration for men (r = 0.85) and
women (r = 0.80).
A later study by Hirvonen and colleagues
(1992) measured the changes in the muscle concentration of ATP, PCr and lactate during a 400m sprint. A 400-m race was performed (time, 51.9
± 0.7 s) and split times for every 100 m recorded.
On subsequent occasions, the six male runners
were required to run 100, 200 and 300 m at the
same speed as their 400-m split times. Biopsies
were taken from the vastus lateralis muscle
before and after each sprint and analysed for PCr
and lactate concentrations. After the first 100 m,
muscle PCr concentration fell from 15.8 ± 1.7–8.3
± 0.3 mmol · kg–1 wet weight (Fig. 41.3), and by
the end of the race, PCr concentration had fallen
by 89% to 1.7 ± 0.4 mmol · kg–1 wet weight. The
average speed over the 400 m decreased after 200
m, even though PCr was not depleted and lactate
was not at maximum level at this point in the race
(Fig. 41.3). The rate of muscle lactate accumulation for the first 100 m was about half that during
Phosphocreatine (mmol.kg–1 dm)
60
60
8.06 m.s–1
40
40
8.3 m.s–1
7.64 m.s–1
20
20
7.01 m.s–1
0
0
100
200
300
400
0
500
Distance (m)
Fig. 41.3 Muscle phosphocreatine (䊐) and lactate
concentrations (䊊) at various speeds during a
simulated 400-m track sprint (Hirvonen et al. 1992).
Muscle lactate (mmol.kg–1 dm)
80
80
537
the two subsequent sections of the race (100–200
and 200–300 m), showing an increased contribution of anaerobic glycolysis to energy production
up to this point. The rate of ATP yield from glycolysis was maximal between 200 and 300 m, as
indicated by the highest rate of lactate accumulation in muscle and blood during this point in the
race. Over the last 100 m, the rate of glycolysis
declined, resulting in a dramatic decrease in
running speed.
Metabolic responses to sprinting
in the laboratory
The development of specific and sensitive laboratory methods to study sprinting provides an
opportunity to examine this form of activity in
a controlled way (Bar-Or 1978; Lakomy 1986,
1987; Falk et al. 1996).
Sprinting has been studied in the laboratory
using a non-motorized treadmill (Lakomy 1987).
In the study by Lakomy (1987), performance and
metabolic responses during two 30-s sprints
were compared. Seven male national level
sprinters, whose specialist events ranged from
100 to 400 m, performed one sprint on a nonmotorized treadmill, and a second sprint on a
running track. Although peak speed and mean
speed were slower on the treadmill than on the
track, there was no difference in the number of
strides taken. In addition, similar physiological
and metabolic responses to both runs were
observed, demonstrating that the treadmill
sprint was a useful tool for the analysis of
the physiological demands of sprint running
in the laboratory. Postexercise blood lactate concentrations were 16.8 vs. 15.2 mmol · l–1 for treadmill and track runs, respectively. Heart rate
averaged 198 beats · min–1 in both 30-s sprints,
and postrace blood glucose concentration was
6.4 ± 1.1 mmol · l–1 after the treadmill run, and
6.2 ± 1.0 mmol · l–1 after the track run (H.K.A.
Lakomy, unpublished observations).
Cheetham et al. (1986) examined performance
during, and the changes in muscle metabolites
following, a 30-s sprint on a non-motorized
treadmill. Peak power output for eight female
538
sport-specific nutrition
subjects was 534 ± 85 W and was 50% of its peak
value at the end of the sprint. Biopsy samples
were taken from the vastus lateralis muscle
before and after the sprint. Muscle glycogen, PCr
and ATP declined from resting values by 25%,
64% and 37%, respectively. Three minutes after
exercise, muscle and blood lactate increased to
78 ± 26 mmol · l–1 and 13 mmol · l–1, respectively.
Similar intramuscular lactate concentrations of
73.9 ± 16.1 mmol · kg–1 dry matter were observed
for males by Jacobs et al. (1983) after 30 s of
maximal cycling using the Wingate anaerobic
test (WAnT) protocol. Blood pH decreased by
0.24 units to 7.16 ± 0.07 3 min after the sprint, and
heart rate increased over the 30-s sprint, reaching
its maximum of approximately 182 beats · min–1
over the last few seconds of the sprint (Cheetham
et al. 1986). Anaerobic glycogenolysis supplied
64% of the ATP required during the 30-s sprint,
calculated from the changes in muscle glycogen,
lactate, pyruvate and PCr concentrations. Similar
metabolic responses to sprinting were observed
in a later study from the same laboratory (Nevill
et al. 1989).
Costill et al. (1983) examined muscle and blood
pH along with blood lactate concentration and
pH after sprint running. Four male subjects were
biopsied from the gastrocnemius muscle before
.
and after a treadmill sprint run at 125% Vo2max.
and a 400-m timed run on a track. After the 400-m
sprint, muscle pH in four of the subjects
averaged 6.63 ± 0.03 and blood pH and lactate
concentration were 7.10 ± 0.03 and 12.3 mmol · l–1,
respectively, highlighting the extensive metabolic challenge of this event.
Thirty seconds of treadmill sprinting also provokes a marked increase in endocrine response.
Plasma noradrenaline and adrenaline increased
from resting values by six- and sevenfold, respectively, and the plasma concentration of bendorphin doubled following 30 s of treadmill
sprinting. (Brooks et al. 1988). Plasma growth
hormone is elevated to more than eight times its
resting value following a 30-s treadmill sprint
(Nevill et al. 1996). The concentration peaked
after 30 min recovery and remained significantly
elevated above baseline for the 60 min. A greater
endocrine response is observed when maximal
sprints are repeated after a short recovery
(Brooks et al. 1990). In one study, nine men and
nine women performed 10 6-s sprints on a nonmotorized treadmill, with 30 s separating each
sprint. Peak plasma adrenaline was 9.2 ± 7.3 for
the men and 3.7 ± 2.4 nmol · l–1 for the women,
and was recorded after only five sprints (Brooks
et al. 1990).
Most studies reporting the metabolic
responses to sprinting have analysed muscle
samples which contain a mixture of fibre types.
However, studies which have been carried out in
vitro have suggested that maximal power output
and its decline are related to fibre type (Faulkner
et al. 1986). Energy metabolism in single muscle
fibres was measured in a study by Greenhaff and
colleagues (1994). Muscle biopsies were taken
from the vastus lateralis muscle before and after
30 s of maximal treadmill sprinting and the type I
and type II fibres analysed for concentrations of
ATP, PCr and glycogen (Fig. 41.4). Prior to the
sprint, PCr and glycogen concentrations were
highest in the type II fibres and a greater decline
was observed in these fibres after the 30-s sprint.
Peak power output declined by 65 ± 3% during
exercise. Phosphocreatine was almost depleted
after the sprint, but those subjects with the higher
type II fibre PCr content showed a smaller
decline in power output during the sprint
(r = –0.93; P < 0.01). The decline in ATP during the
sprint was similar in both fibre populations. This
illustrates the importance of the contribution
of PCr to energy production during maximal
exercise.
Fatigue during sprinting
Elite male sprinters can maintain maximal speed
for 20–30 m, whereas females can maintain top
speed for only 15–20 m. The explanation, even in
elite sprinters, may be due to both mechanical
and metabolic factors.
The mechanical limitations to sprinting
include failure of neuromuscular coordination
(Murase et al. 1976), the change in body position
relative to the foot striking the ground, and
deceleration caused by the grounding foot
(Mann & Sprague 1983; Mann 1985). At such
sprinting
100
539
1000
75
*
800
50
600
Power output (W)
Fig. 41.4 Muscle
phosphocreatine concentrations
in type I ( ) and type II ( )
fibres before and after a 30-s
sprint on a non-motorized
treadmill (Greenhaff et al. 1994).
*, P < 0.01, type I vs. type II.
Phosphocreatine (mmol.kg–1 dm)
Peak power
25
400
*
End power
0
high velocities, it is difficult to maintain such a
high limb speed, both in recovery of the driving
leg, and in the brief track contact time for force
generation (Radford 1990).
Air resistance at high velocities may also be a
significant factor in sprinting because it increases
with running speed. Davies (1980) calculated
that elite 100-m sprinters running 10 m · s–1
would run 0.25–0.5 s faster if they did not have to
overcome air resistance. Pugh (1970) estimated
that air resistance accounted for 16% of the total
energy expended to run 100 m in 10.0 s. Thus, it is
advantageous to perform sprints at high altitude.
For example, the altitude of Mexico City (2250 m)
provides an advantage of approximately 0.07 s
(Linthorne 1994).
The metabolic factors contributing to the onset
of fatigue are associated with the decrease of
PCr or ATP in the muscle (Murase et al. 1976;
Hirvonen et al. 1987, 1992). The consequent
decrease in the availability of high-energy phosphates within exercising muscles results in a
reduction in the power output. During the
middle part of the 100-m sprint, running speed
decreases as the contribution of the high-energy
phosphate stores is reduced (see Fig. 41.1), and at
the end of the 100-m race, anaerobic glycolysis is
the main energy source (Hirvonen et al. 1987). A
decline in running speed or power output
towards the end of a 400-m race and a 30-s tread-
Pre-exercise
Postexercise
mill sprint is also associated with very low PCr
values (Hirvonen et al. 1992; Greenhaff et al.
1994).
The importance of PCr is highlighted because
power output declines when PCr utilization
decreases, despite adequate stores of ATP and
glycogen. For example, during a maximal 30-s
treadmill sprint, muscle glycogen was reduced
by 27% and 20% in type II and type I fibres,
respectively (Greenhaff et al. 1994). ATP
decreased by a similar amount (20%) in both fibre
types. After 30 s of sprint cycling, there was still
sufficient glycogen and ATP left in both fibre
types in the muscle to sustain energy metabolism
(Boobis et al. 1987; Vollestad et al. 1992). Why,
then, do the sprinters fatigue when substrate is
still available for energy metabolism? A possible
answer is that initial force generation is dependent on the availability of PCr, once intramuscular PCr stores are depleted. Sprinting speed
cannot be maintained because the available
glycogen cannot be used quickly enough to
sustain the high rates of ATP utilization required.
In addition, accumulation of inorganic phosphate (Pi) may inhibit the cross-bridge recycling
between actin and myosin filaments directly
(Hultman et al. 1987).
The decline in running speed observed
towards the end of a 400-m race is due to a reduction in the rate of glycogen hydrolysis, despite
540
sport-specific nutrition
ample availability of muscle glycogen. The parallel increase in hydrogen and lactate ions during
sprinting may inhibit glycolysis, thus contributing to the development of fatigue (Sahlin 1996). A
further explanation for fatigue during the 400-m
sprint and repeated shorter sprints during training is that the increase in ammonia observed as a
consequence of decreases in PCr and ATP concentrations during sprinting (Schlict et al. 1990;
Tullson & Turjung 1990) may be implicated in the
fatigue process (Green 1995).
Influence of sprint training on
energy production
The main focus of many studies on the adaptations to sprint training is the changes in energy
metabolism underpinning improvements in performance. This approach has led to a greater
understanding of the metabolic causes of fatigue
during sprinting.
The main and consistent finding in the laboratory and in the field is that sprint training improves performance. This performance is
measured as an increase in maximum power
output during the initial period of exercise, an
increase in the amount of work done during a
brief exercise bout, or an increase in exercise
duration at high exercise intensities (Brooks et al.
1993).
Nevill et al. (1989), investigated the effect of 8
weeks of high-intensity training on metabolism
during a 30-s treadmill sprint. Sixteen matched
subjects were assigned to either a training or a
control group. After training, peak power
increased by 12% during the initial period of
exercise, and the total work done during the
test was increased by 6%. This improvement
in performance was equivalent to a 1.5-s reduction in 200-m running time. Maximum muscle
lactate concentration increased by 20% after
training, and an equivalent increase in the rate
of ATP resynthesis from anaerobic glycolysis
was also observed. The excess postexercise
oxygen consumption also increased by 18%
after training. However, despite the increase in
muscle lactate concentration, training did not
change muscle pH during maximal treadmill
sprinting.
The increased ATP required as a consequence
of the improvement in performance after sprint
training was provided from anaerobic glycolysis
(Nevill et al. 1989). No changes were observed in
the contribution from PCr or aerobic metabolism.
The increased resynthesis from anaerobic glycolysis was facilitated by an increase in the activity
of phosphofructokinase (PFK), the rate-limiting
enzyme in anaerobic glycolysis, and by an
increased efflux of H+ from the muscle cell after
training. This is in agreement with other studies,
which have reported that adaptations to sprint
training include an increase in the muscle’s
buffering capacity (Sharp et al. 1986), an increase
in the activity of muscle PFK (Fournier et al. 1982;
Roberts et al. 1982; Sharp et al. 1986; Jacobs et al.
1987), and an increase in the proportion of type
IIa fibres (Jacobs et al. 1987).
However, factors other than increased anaerobic energy production may also contribute to
improvement in performance after sprint training. These include an improved regulation of
K+ during exercise and changes in the Na+–K+ATPase concentrations (McKenna et al. 1993),
which are important in the excitation–contraction coupling in skeletal muscles. Other factors
include the determinants of muscle tension at
both the whole muscle and single fibre level.
These include action-potential frequency, fibre
length and fibre diameter. It is beyond the scope
of this review to consider these factors, which are
discussed in detail elsewhere (Brooks et al. 1993).
Nutritional influences on sprinting
Dietary intake
In contrast to the plethora of information on
the dietary intake of endurance athletes, the
nutritional habits of sprinters are not well
documented. It is a well-established belief in the
power- and strength-training community that
strength is improved when a diet high in protein
is consumed. Quantitatively, the recommended
protein intake for these athletes is about 1.4–1.7 g
sprinting
protein · kg–1 body mass · day–1 (Lemon 1992). A
diet containing 12–15% of its energy from protein
should be adequate for strength athletes (including sprinters), assuming that the total energy
intake is sufficient to cover their high daily
energy expenditure (Lemon & Proctor 1991).
Should sprinters consume a particular type of
diet? Total energy intake should be increased in
order to cover the demands of training and competition. Most of the studies which have reported
the energy intakes of runners have focused on
endurance athletes. One study of trained university track athletes (Short & Short 1983) reported
that the daily energy intake of these sprinters
was approximately 16.8 MJ (4000 kcal), similar to
the energy intake of university bodybuilders in
the same study. Unfortunately, no data on the
physical characteristics of these athletes were
documented. A well-balanced diet, containing a
wide variety of foods, is all that is recommended
to ensure that all needs for energy, vitamins and
minerals are met. At least 60–70% (7–8 g · kg–1) of
daily energy intake should come from carbohydrates, about 12% from protein (1.2–1.7 g · kg–1),
and the remaining energy provided by fat
(Devlin & Williams 1991; Lemon 1992). However,
only endurance athletes seem to comply with
these recommendations (C. Williams 1993). The
only nutrient supplementation which may
enhance sprinting is creatine (see Chapter 27)
and bicarbonate (see Chapter 29). Currently,
there is little evidence to suggest that sprinters
require any other supplements (including vitamins and minerals) in addition to a normal balanced diet containing a wide range of foods
covering the individual’s energy requirements.
Further research is necessary to establish
whether some nutrients and combinations
of nutrients have an ergogenic effect during
sprinting.
Carbohydrate loading and sprinting
Muscle glycogen ‘supercompensation’ improves
performance during prolonged exercise (Costill
1988), and is a nutritional strategy used by
endurance athletes in preparation for competi-
541
tion. The importance of the initial glycogen
concentration on the performance of maximal
or high-intensity exercise remains an issue,
although it is clear that very low pre-exercise
glycogen concentrations are associated with
reductions in performance in high-intensity
exercise (Maughan & Poole 1981; Pizza et al.
1995). However, it is unlikely that increased
glycogen stores will affect sprinting performance, as glycogen per se is not a limiting factor
during sprints over distances of 400 m or less
(Hirvonen et al. 1992). Laboratory studies on
brief, maximal exercise also support this conclusion. The mean and peak power outputs of
athletes performing 30 s of maximal exercise
using the WAnT protocol on a cycle ergometer
were unchanged after carbohydrate loading
(Wootton & Williams 1984).
This lack of ergogenic effect is elucidated when
the metabolic responses to sprinting are examined in single fibres of human skeletal muscle
(Greenhaff et al. 1994). Biopsies were obtained
from six subjects before and after a 30-s sprint
on a non-motorized treadmill. Glycogen was
reduced by 20% and 27% in the type I and type II
fibres, respectively, in agreement with the significant contribution from muscle glycogen during a
30-s sprint reported by Cheetham et al. (1986).
However, the 65% decline in power output
during the 30-s sprint was probably associated
with the large decline in PCr concentration in
both type I fibres (83% decrease), and particularly the type II fibres (94% decline).
Varying the carbohydrate intake in the days
before exercise has been shown to influence performance during high-intensity (not maximal)
exercise when undertaken either continuously
(Maughan & Poole 1981; Pizza et al. 1995), or
intermittently (Bangsbo et al. 1992; Nicholas et al.
1997). However, a relationship between carbohydrate status and exercise performance during
maximum exercise has not been consistently
reported (Symons & Jacobs 1989; Vandenberghe
et al. 1995). There may, however, be a critical
concentration of glycogen below which highintensity exercise is impaired. Indeed, it has been
shown that below a muscle glycogen concentra-
542
sport-specific nutrition
tion of 20–30 mmol · kg–1 of wet weight, the rate
of energy production is reduced and performance decreased (Costill 1988).
fourth bout (McCartney et al. 1986). Changes in
muscle glycogen, lactate and glycolytic intermediates suggested that the rate of glycogenolysis
was limited at the PFK level during the first and
second exercise periods, and at the phosphorylase level in the third and fourth exercise periods
(McCartney et al. 1986). In agreement with these
findings, Spriet et al. (1989) reported that muscle
[H+] was higher and the glycolytic flux lower
after the third exercise bout than after the second,
even though ATP and PCr degradation was
similar in the two exercise bouts. As a consequence of the reduction in the rate of glycolysis
during the third and fourth sprints, there is a
greater reliance on aerobic metabolism (Fig.
41.5), and possibly the intramuscular triglyceride
stores (McCartney et al. 1986).
The laboratory studies on repeated sprints of
30 s duration are relevant to training sessions
where sets of 200 or 300 m are performed.
However, muscle metabolism during repeated
shorter sprints (< 6 s) has a wider applicability,
not only for sprint training, but also to the multiple sprint sports. Gaitanos et al. (1993) examined
muscle metabolism during intermittent maximal
exercise. The exercise protocol consisted of 10 ¥
Carbohydrate loading and repeated sprints
Sprint training involves many sprints during
daily training sessions. The metabolic and physiological responses to repeated sprints performed
in the laboratory (Gaitanos et al. 1993; Trump et
al. 1996) provide some information on the glycogen demands of a sprint training session, or in
sports such as soccer or rugby (Nicholas et al.
1994), where maximal sprints are performed
briefly between periods of less intense exercise
over an 80–90-min period.
Several studies have examined maximal
dynamic muscle power output and the associated metabolic changes in muscle during three to
four bouts of maximal cycling at 100 r.p.m.
(10.5 rad · s-1), separated by 4-min recovery intervals (McCartney et al. 1986; Spriet et al. 1989;
Trump et al. 1996). In these studies, power output
and work done decreased by 20% in both the
second and third exercise periods, but there was
no further decrement in performance in the
1800
PPO
1600
75
1400
50
1200
25
1000
18.2
14.8
–2
3
Sprint 1
Sprint 2
Sprint 3
Sprint 4
0
800
Rest
Sampling time
Peak power (W)
Glycogen concentration (mmol.kg–1 wet wt)
100
Fig. 41.5 Post-sprint glycogen
concentration and power output
during four bouts of 30-s
isokinetic cycling (McCartney et
al. 1986). The amount of glycogen
utilized during each bout is also
shown (in mmol · kg-1 wet wt).
PPO, peak power output.
sprinting
6-s maximal sprints on a cycle ergometer with
30 s of recovery between each sprint. The applied
load for the sprints was calculated as for the
WAnT protocol (75 g · kg–1 body mass). Biopsies
were taken from the vastus lateralis muscle
before and after the first sprint and 10 s before
and immediately after the 10th sprint. Mean
power output generated over the first 6-s sprint
was sustained by an equal contribution from PCr
degradation and anaerobic glycolysis. By the end
of the first sprint, PCr and glycogen concentration decreased by 57% and 14%, respectively, of
resting values, and muscle lactate concentration
increased to 28.6 mmol · kg–1 dry matter, an indication of significant glycolytic activity. However,
in the 10th sprint, mean power output was
reduced to 73% of that generated in the first
sprint, despite the fact that there was a dramatic
reduction in the energy yield from anaerobic glycolysis. Thus it was suggested that power output
during the last sprint was supported by energy
that was mainly derived from PCr degradation
and an increased aerobic metabolism.
Thus the weight of available evidence shows
that it is unlikely that sprinting is limited by
muscle glycogen availability, unless the glycogen
concentration falls below a critical threshold
value of 100 mmol · kg–1 of dry matter. Glycogen
availability is also unlikely to limit peak power
output during repeated sprints because of the
decline in glycogenolysis and lactate production
observed under these conditions. However, as
reviewed in the next section, evidence shows that
an inadequate intake of carbohydrate in the diet
is detrimental to sprinting.
Carbohydrate intake and repeated
maximal sprints
An inadequate carbohydrate intake has been
shown to decrease performance during a second
maximal cycle ergometer interval test performed
2–3 days after the first test (Fulcher & Williams
1992; Jenkins et al. 1993). Fulcher and Williams
(1992) studied the effects of 2 days’ intake of
either a normal carbohydrate (450 ± 225 g) or a
low carbohydrate (71 ± 27 g) diet on power
543
output during maximal intermittent exercise.
Two trials were performed, one before, and then
one following the 2 days of dietary manipulation. The test protocol comprised five sets of
five all-out fixed level sprints with 30 s recovery
(65 g · kg–1 applied load) separated by 5 min
active recovery. A final, sixth set comprised 10 ¥
6-s sprints, separated by 30 s recovery. Those subjects who ate their normal amount of carbohydrate showed a significant improvement in peak
power output during the five sets of sprints in
test 2 compared with test 1. No such improvement was shown in test 2 after the low carbohydrate diet. In the study by Jenkins and colleagues
(1993), 14 moderately trained individuals completed two intermittent exercise tests, separated
by 3 days. Each test comprised five bouts of 60-s
cycle performed maximally, with successive
exercise periods separated by 5 min of passive
recovery. During the 3-day period between trials,
each subject was randomly assigned to either a
high carbohydrate (83%), moderate carbohydrate (58%) or low carbohydrate (12%) diet.
Although performance declined in the low carbohydrate condition in both these studies, the
amount of carbohydrate ingested (10% and 12%,
respectively, of total energy intake) was significantly lower than the amount normally consumed by athletes. Nevertheless, these studies
highlight the importance of an adequate intake
of dietary carbohydrate for those individuals
performing repeated sprint exercise.
These results emphasize the need for sprinters
in training, and sportsmen and women competing in the multiple sprint sports (see Chapter 45
for a more detailed review) to consume adequate
amounts of carbohydrate on a daily basis. Much
research has been carried out to determine the
amount of carbohydrate needed to replenish
glycogen stores within 24 h of intense training.
A diet which comprised approximately 8–10 g
carbohydrate · kg–1 body mass was sufficient
to replace muscle glycogen stores after daily 1-h
training sessions (Pascoe et al. 1990). Highintensity endurance capacity was also improved
following a high carbohydrate recovery diet
(Nicholas et al. 1997). However, some studies
544
sport-specific nutrition
have shown that when a fixed amount of exercise
is performed on a daily basis, performance is not
affected when only a moderate amount of carbohydrate is consumed (Simonsen et al. 1991; Nevill
et al. 1993; Sherman et al. 1993).
Nevill et al. (1993) reported that power output
during 1 h of intermittent sprint exercise was
unchanged after the carbohydrate intake was
manipulated during the 24-h recovery (Fig. 41.6).
During the first trial, 18 games players performed 30 maximum 6-s sprints, interspersed
with walking and jogging, on a non-motorized
treadmill. The subjects were then randomly
assigned to three equally matched groups and
repeated the test 24 h later, after consuming
either a high, low or normal carbohydrate diet
(79 ± 3%, 47 ± 8%, 12 ± 1% carbohydrate, respectively). Power output over the 30 sprints was not
different between trials; however, the high carbohydrate group did perform better than the low
carbohydrate group over the first nine sprints.
However, although no performance decrements were observed in the short term, an
increased carbohydrate intake is recommended
because it may improve performance after an
800
Mean power (W)
700
600
500
400
Trial 1
Trial 2
Fig. 41.6 Mean power output during 30 maximal 6-s
sprints during trial 1 and trial 2 for three dietary
groups: , high carbohydrate; 䊐, normal
carbohydrate; , low carbohydrate (Nevill et al. 1993).
intensive training period (Simonsen et al. 1991).
Laboratory studies have shown that one 6-s
sprint reduces glycogen by approximately
44 mmol · kg–1 dry matter (14%), and after 10
sprints, glycogen is reduced by 36% (Gaitanos et
al. 1993). A sprinter may train intensively — say,
three to five times per week — which may cumulatively reduce glycogen stores, leading to glycogen depletion. Performance during maximal
exercise may be reduced by 10–15% when
glycogen concentration falls below a critical
threshold (Jacobs et al. 1982). Although there is
no ergogenic benefit of carbohydrate loading in
the days prior to a single sprint, an adequate carbohydrate intake is recommended for sprinters
in training to support the intense daily training
sessions.
Dietary supplements and sprinting
Protein and amino acids
Anabolic steroids, used by bodybuilders to
increase lean muscle tissue, are illegal in sporting
competition, and may pose a number of health
risks. A variety of nutrients are believed to
provide an effective, safe and legal alternative
instead (M.H. Williams 1993). Amino acid supplements have been advertised for strength athletes because they are said to provide a safe
anabolic or muscle-building effect. The two most
commonly used amino acids are arginine and
ornithine because of their stimulatory effects on
human growth hormone (HGH) production
(Hatfield 1987; Williams 1989). It is well
documented that exogenous growth hormone
produces anabolic effects in growth hormonedeficient animals and humans, but it is questionable as to whether this same effect exists in
normal animals and humans.
However, many athletes believe that supplementation with these amino acids stimulates
the release of HGH, which is thought to act by
increasing insulin-like growth factors (IGF1 and
IGF2). Thus, protein and nucleic acid synthesis is
stimulated in skeletal muscle (Lombardo et al.
1991). However, many well-controlled studies
sprinting
have failed to observe an increase in the serum
concentration of HGH following supplementation with these amino acids. Those studies which
have shown some anabolic effect of these amino
acid supplements are flawed. Suminski et al.
(1997) found that the ingestion of 1500 mg of arginine and 1500 mg of lysine immediately before
resistance exercise did not alter exercise-induced
changes in the concentration of growth hormone
in weight-training males. When the same amino
acid mixture was ingested under basal conditions, the secretion of growth hormone was
increased to levels which were higher than after
ingestion of a placebo, 60 min after amino acid
ingestion during resting conditions. Additional
research is required to evaluate claims for commercial products.
A few studies have examined the effect of arginine and/or ornithine supplementation on body
composition, measures of muscular strength or
power and reported significant increases in lean
body mass. Where increases in lean body mass
have been reported (Crist et al. 1988; Yarasheski
et al. 1992), the functional ability of the muscle
was not assessed. M.H. Williams (1993) emphasizes the flawed experimental methodology in
each study, thus questioning the interpretation of
the findings. Although statistical significance
was reported in two of the studies, a recalculation, using the appropriate statistical technique,
actually revealed no significant differences
between the supplement and the placebo. Other
studies have reported no significant effect of
arginine or a mixture of amino acids on measures
of strength, power or HGH in experienced
weightlifters (Hawkins et al. 1991; Warren et al.
1991). The use of both HGH and anabolic
steroids is contraindicated for athletes, since they
are both proscribed by the IOC and both carry
significant health risks (Lombardo et al. 1991;
M.H. Williams 1993).
The ergogenic effect of supplementing the diet
with low-dose oral amino acids has been questioned (Fogelholm et al. 1993; Fry et al. 1993;
Lambert et al. 1993). Fogelholm et al. (1993) found
no difference in the concentrations of serum
growth hormone or insulin of competitive
545
weightlifters following 4 days supplementation
with l-arginine, l-orthinine and l-lysine. This
result was consistent with the findings of
Lambert et al. (1993), who reported that serum
growth hormone concentrations were not elevated in male bodybuilders after the ingestion
of commercial amino acid supplements in the
quantities specified by the manufacturers. The
supplements of amino acids comprised two
mixtures: 2.4 g of arginine and lysine, and 1.85 g
of ornithine and tyrosine.
Fry and colleagues monitored both hormonal
and performance responses to amino acid supplementation in parallel with high-volume training. In this study, 28 elite junior weightlifters
were tested for strength before and after 7 days of
high-volume training sessions. During this 7-day
training period, the subjects’ diets were supplemented with capsules containing either amino
acids (protein group) or lactose (placebo group).
The protein group took 2.4 g of amino acids (containing a mixture of all 20 amino acids) immediately prior to their three daily meals for 7 days,
as well as 2.1 g of branched-chain amino acids
(l-leucine, l-isoleucine, l-valine, supplemented
with l-glutamine and l-carnitine), prior to each
training session. It was concluded that hormonal
responses, both at rest and following training,
were unaltered.
It is important to recognize that brief periods
of high-intensity exercise significantly increase
the concentration of growth hormone. Growth
hormone increased and remained approximately
10 times the basal value in sprint-trained
athletes, 1 h after a maximal 30-s sprint on a
non-motorized treadmill (Nevill et al. 1996). The
growth hormone response was greater in sprinttrained than endurance-trained athletes, and no
differences were found between males and
females. Peak power output and the magnitude
of metabolic response to the sprint accounted
for 82% of the variation in serum peak growth
hormone response. Thus, sprint training per se is
effective in increasing growth hormone. Whether
or not sprinting could promote increases in IGF1
and IGF2 is unknown, but repeated eccentric
contractions have been shown to increase the
546
sport-specific nutrition
immunoreactivity of IGF1 in muscle 4 days after
exercise (Yan et al. 1993).
In summary, a high carbohydrate diet is recommended in order to replenish the muscle
glycogen depleted during intense training sessions on a daily basis. With the exception of creatine supplementation (reviewed in Chapter 27)
and bicarbonate supplementation (reviewed in
Chapter 29), there is little evidence to suggest
that sprinters need any additional nutrient supplementation (including vitamins and minerals)
provided that they eat a normal balanced diet,
containing a wide range of foods, which covers
the individual’s energy requirements (Clarkson
1990; Van Der Beek 1990).
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