"Легкоатлетического вестника ИААФ" 4-2009 - Московский ...

Средние и длинные дистанции
factors, including the removal of lactate and the
buffering of metabolic acidosis, the amount of
carbohydrate
(glycogen) stored in skeletal muscles, as well
the ability to metabolise fat. An important role is also
played by the neuromuscular system to the extent
that, for force production to continue and for athletes
to maintain their pace, the central nervous system
has to increase the number of motor units recruited
and increase the frequency of stimulation of the
motor units. In accordance with these physiological
influence factors endurance training is oriented: Long
intervals (3-5 min) run at the velocity at which
VO2max occurs provides the greatest cardiovascular
load because athletes repeatedly reach and sustain
their maximum stroke volume, cardiac output, and
their VO2max during the work periods. Long intervals
are the most potent stimulus for improving VO2max.
However, short intervals (shorter than 2 min) can also
improve VO2max, as long as the intervals are performed
at a high intensity and with short, active
recovery periods to keep VO2 elevated throughout
the workout. A large volume of endurance training
may be the simplest way to increase the muscular
factors associated with endurance (mitochondrial
and capillary density and enzyme activity). Interval
training has also been shown to increase aerobic
enzyme activity. Running at the lactate threshold
increases it to a faster speed and higher percentage
of VO2max, making what was an anaerobic intensity
before now high aerobic. The neuromuscular system
can be positively influenced by high amounts of training
(improvement of running economy), but can also
be optimised through a target-oriented speedstrength
training. For example, it has been shown
that explosive strength training with heavy weights
and plyometric training improve economy in
endurance athletes.
Kemmler, W.; Stengel, S. v.; K ckritz, C.;
Mayhew, J.; Wassermann, A.; Zapf, J.
Effect of compression stockings on running
performance in men runners
The Journal of Strength and Conditioning Research, 23,
(2009),
1, pp. 101-105
The purpose of this study was to determine the
effect of below-knee compression stockings on running
performance in men runners. Using a withingroup
study design, 21 moderately trained athletes
(39.3 ± 10.9 years) without lower-leg abnormities
were randomly assigned to perform a stepwise
treadmill test up to a voluntary maximum with and
without below-knee compressive stockings. The
second treadmill test was completed within 10 days
of recovery. Maximum running performance was
determined by time under load (minutes), work (kJ),
and aerobic capacity (ml/kg/min). Velocity (km/h)
and time under load were assessed at different
metabolic thresholds using the Dickhuth et al. lactate
threshold model. Time under load (36.44 vs.
35.03 minutes, effect size [ES]: 0.40) and total work
(422 vs. 399 kJ, ES: 0.30) were significantly higher
with compression stockings compared with running
socks. However, only slight, nonsignificant differences
were observed for VO2max (53.3 vs. 52.2
ml/kg/min, ES: 0.18). Running performance at the
anaerobic (minimum lactate + 1.5 mmol/L) threshold
(14.11 vs. 13.90 km/h, ES: 0.22) and aerobic
(minimum lactate + 0.5 mmol/L) thresholds (13.02
vs. 12.74 km/h, ES: 0.28) was significantly higher
using compression stockings. Therefore, stockings
with constant compression in the area of the calf
muscle significantly improved running performance
at different metabolic thresholds. However, the
underlying mechanism was only partially explained
by a slightly higher aerobic capacity.
Kenefick, R. W.; Cheuvront, S.; Sawka, M. N.
Thermoregulatory function during the
marathon
Sports Medicine, 37, (2007), 4/5, pp. 312-315
Marathon races are performed over a broad range of
environmental conditions. Hyperthermia is a primary
challenge for runners in temperate and warm weather,
but hypothermia can be a concern during coolwet
or cold conditions. Body temperature during the
marathon is a balance between metabolic heat production
and exchange with the environment
described by the heat balance equation. During
exercise, core temperature is proportional to the
metabolic rate and largely independent of a wide
range of environmental conditions. In temperate or
cool conditions, a large skin-to-ambient temperature
gradient facilitates radiant and convective heat loss,
and reduces skin blood flow requirements, which
may explain the tolerance for high core temperature
observed during marathons in cool conditions. However,
in warmer environments, skin temperatures
and sweating rates increase. In addition, greater skin
blood flow is required for heat loss, magnifying
thermoregulatory
and circulatory strain. The combined
challenge of exercise and environment associated
with marathon running can substantially challenge
the human thermoregulatory system.
Kenefick, R. W.; Sawka, M. N.
Heat exhaustion and dehydration as causes
of marathon collapse
Sports Medicine, 37, (2007), 4/5, pp. 378-381
This article reviews causes of marathon collapse
related to physical exhaustion, heat exhaustion and
dehydration. During severe exercise-heat stress
(high skin and core temperatures), cardiac output
can decrease below levels observed during exercise
in temperate conditions. This reduced cardiac output
and vasodilated skin and muscle can make it difficult
to sustain blood pressure and perhaps cerebral
blood flow. Dehydration can accentuate this
cardiovascular
strain. In contrast, excessive heat loss to
the environment during cold weather may result in
hypothermic collapse. Other factors contributing to
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post-race collapse might include reduced skeletal
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