The effects of partial sleep restriction on biomechanical, physiological, and perceptual responses during an early morning treadmill run
T Steenekamp; J Davy
Department of Human Kinetics and Ergonomics, Rhodes University, Grahamstown
Corresponding Author Travis Steenekamp Department of Human Kinetics and Ergonomics Rhodes University Grahamstown
[email protected]
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Abstract Purpose: The aim of this study was to investigate whether a single night of partial sleep restriction would affect biomechanical, physiological, and perceptual factors during a fixed early morning treadmill running protocol. Method: Eight recreationally active males performed two 6-minute early morning, fixed-pace, flat runs, set at 60% of their maximal treadmill running speed. Each run was preceded by one of two sleep conditions – a sleeprestricted night where participants’ sleep was limited to 4 hours in bed, and a control night where participants were allowed a normal night’s sleep at home. Stride length, cadence, heart rate, energy expenditure, and ratings of perceived exertion (RPE) were recorded during both protocols. Results: There were no significant differences observed between the two conditions with respect to stride length, cadence, heart rate, energy expenditure, or RPE. Conclusion: Sleep restriction of 4 hours does not affect biomechanical, physiological, or perceptual responses to early morning fixed treadmill running. Key words: PARTIAL SLEEP RESTRICTION, SLEEP LOSS, RUNNING
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al., 2014(b); Sargent et al., 2014). Previous
Introduction
research in this area has focused mostly on Sleep is recognised as a necessity for understanding the effects of sleep deprivation effective development, growth, recovery, and (when sleep is curtailed for 24 hours or energy conservation, even though its role in longer) on performance in a variety of these processes is not fully understood contexts (Martin, 1981; Martin and Haney, (Mignot, 2008). Generally, 8 hours of sleep 1982; Souissi et al., 2003; Oliver et al., 2009; per night is recommended to maintain health Skein et al., 2011, Temesi et al., 2013). and alertness each day (Balkin et al., 2008). However, this is typically not the reality of Getting less than this recommendation (or what
athletes
(elite
or
amateur)
may
what is necessary for each individual) has experience prior to training or competition; been associated with a number of negative partial metabolic
(Van
Cauter
et
al.,
sleep
loss,
either
through
sleep
2008), restriction or sleep fragmentation, is more
cardiovascular (Meier-Ewert et al., 2004), likely (Mougin et al., 1991). In addition to this, mood (Scott et al., 2006) and cognitive the nature of the physical activity has been (Rogers et al., 2003) outcomes, which would either time to failure (Martin, 1981; Mougin et affect performance proficiency and health. al., 1991; Temesi et al., 2013) or of high This is evident in the working context (Costa, intensity (Souissi et al., 2003; Skein et al., 2010; Uehli et al., 2014) but the role of sleep 2011), with few studies exploring the effects of and the effects of sleep loss on athletic sleep loss on submaximal performance and performance and recovery remain unclear responses (Oliver et al., 2009). As such, the (Leeder et al., 2012; Lastella et al., 2014 (a); effect of partial sleep loss on responses to Halson, 2014), despite athletes and coaches submaximal physical performance needs to emphasising the importance of sleep for be understood more fully. Therefore, the aim effective training and competition (Lastella et of the current investigation was to understand al., 2014 [a]). the impact of a single night of acute sleep Sleep loss in athletes can occur for a number
restriction
of reasons. These include early morning
biomechanical
training (Sargent et al., 2014), trans-meridian
during an early morning fixed treadmill
travel, sleeping in a foreign environment,
running protocol, when compared to non-
on
selected and
physiological,
perceptual
responses
noise, and pre-competition anxiety (Lastella et
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restricted (normal) sleep. It was hypothesised
responses during the run, irrespective of the
that
fact that the run was of a fixed duration and
sleep
restriction
may
alter
the
biomechanical, physiological and perceptual
relativised intensity.
Methods
of sleep; participants were encouraged to obtain a normal night’s sleep, keeping in mind
Experimental design their scheduled run time. This information was Eight recreationally active males participated
recorded
(23 ± 4 years; 78 ± 7 kg; 179 ± 3 cm). All were
participant had to complete.
in
a sleep
diary which each
non-smokers, were in good physical health, The sleep-restricted condition allowed sleep did
not
suffer
from
any
sleep-related
and
were
habitual
for the total time of 4 hours. This condition disorders,
treadmill was housed in a laboratory, which simulated
runners. The study was laboratory-based and an athlete having to sleep in a foreign took the form of a repeated measures design; environment prior to competition. Bed times participants were required to complete two 6during this condition were dependent upon the minute submaximal treadmill runs that were scheduled run time: for runs scheduled at scheduled at either 07h00 or 07h45. Each run 07h00. Participants retired at 02h30, while for was performed following the completion of runs scheduled for 0745, bedtime was 03h15. one of two experimental conditions that were In both instances, this included the 4 hours for separated
by
a
minimum
of
2
days. time in bed and a 30-minute period between
Irrespective of the condition, participants were wakeup time and the running protocol. The required to wake 30 minutes prior to the order in which participants completed the scheduled run and be in the laboratory 10 conditions was randomised, but the scheduled minutes before it. The non-sleep-restricted running time was kept constant for each protocol allowed participants to get what for participant. them was considered to be a normal night’s sleep
in
their
home
environment.
For
students, this would range from 7 to 10 hours
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-1
recorded to determine cadence (steps.min ).
Running protocol parameters
The total distance covered by each participant The 6-minute submaximal flat treadmill run was also recorded, and stride length was was performed at a speed of 60% of each determined by dividing the distance run by the participant’s
maximum
running
speed, cadence.
determined prior to experimentation during a maximal treadmill run. Starting at a speed of 12 km.hr
-1
participants increased their speed
by 1 km.hr
-1
every minute until volitional
Heart rate was measured constantly (Polar F2 watch and Polar T31 transmitter; Polar Electro Oy,
Kempele,
Finland)
treadmill
during
both
the
test
and
the
protocols.
For
the
fatigue (Matter et al., 1987). The speed that
maximal
running
participants could maintain for one minute
experimental
prior to this failure was taken as the maximal
maximal running test, it was used to ensure
running speed, and 60% of this was chosen.
that participants reached their maximum.
This was done in an effort to relativise the
Energy expenditure (Cortex Metalyser 3B
intensity of the running protocol to each
ergospirometry system; CORTEX Biophysik
individual’s capability. With respect to the run
GmbH, Leipzig, Germany) was also monitored
length, 6 minutes was chosen as this would
for the duration of the experimental treadmill
provide enough time to determine the effects
runs. This was derived from the measures of
(if any) of the conditions on steady state
oxygen
responses.
production
running
intake
(VO2),
(VCO2)
and
carbon the
dioxide
Respiratory
Quotient. Prior to data collection, barometric
Selection of dependent variables pressure was calibrated once every two With respect to biomechanical measures,
weeks, as was gas concentration. The flow
each participant’s gait was filmed (using a
sensor (volume measure) was calibrated
Samsung S5 smartphone camera that was
before each testing session.
positioned in front of a treadmill on a tripod) Central perceptions of effort were assessed for
the
duration
of
each
run
and using the Borg Ratings of Perceived Exertion
retrospectively
analysed
to
determine scale (Borg, 1970). Participants were asked to
cadence and stride length. This was achieved point to their levels of perceived exertion each using a step counter; each video was slowed minute during the run. down and the number of steps was manually
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Each participant also received a sleep diary,
was familiarised with the treadmill on which
which required them to record their estimated
they were to run (Cybex Trotter 900T, Cybex
sleep length and quality for the four days
International, Medway, USA). Following this,
before their first condition and on the night of
the maximal treadmill running protocol was
the second condition.
performed to determine each individual’s
While the environmental temperature of the laboratory could not be climate controlled during
the
running
sessions,
both
the
temperature and humidity in the laboratory were
measured
(Cortex
Metalyser
3B
ergospirometry system; CORTEX Biophysik GmbH, Leipzig, Germany). Temperature in o
the laboratory averaged 20.07 (±1.26) C while humidity was 44.17 (±6.59) %. Statistical
experimental running speed. Prior to leaving the laboratory, participants received their sleep diaries and were encouraged not to exercise, or consume any alcohol, stimulants or caffeine 24 hours before the start of each condition. Participants were questioned about their
adherence
upon
returning
to
the
laboratory for each condition.
Data collection
analyses revealed no significant differences in The order in which the conditions were temperature (p=0.5; df=1, 7; F=0.523) or completed
varied
randomly
between
humidity (p=1; df=1, 7; F=0) over all the participants through permutation. For the nontesting days. Only natural light was allowed in restricted
condition,
participants
were
the laboratory during the running sessions as instructed to get a normal night’s sleep at artificial light may have altered participant home. With respect to the sleep-restricted responses during the different conditions. condition, participants arrived at the laboratory
Experimental procedures Following
ethical
at 00h00 before the morning run. Under the
clearance
Department
of
Human
Ergonomics
ethics
from
Kinetics
committee,
the and
student
participants were recruited. Following an initial briefing session, interested participants signed their
consent,
and
basic
demographic
information was collected. Each participant
supervision of a research assistant, they worked, watched movies or read until their bed time. No stimulants, caffeine or food were permitted in the laboratory, so participants were fasted prior to the runs. Water was available ad libitum. The sleeping area was a sectioned off part of the testing laboratory, and only one participant was in the sleep area
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at any one time. Heating facilities ensured that
way analysis of variance was applied to
the area was comfortable, with ample clean
determine
linen
conditions over the 6-minute run. Statistical
being
provided.
Participants
were
both
conditions,
participants
differences
between
the
significance was set at p < 0.05.
permitted to retire at 02h30 or 03h15. For
any
were
required to be awake by 06h30 or 07h15 accordingly and were given 30 minutes to
Results Sleep diary information
prepare for their run, which for the non-sleepSleep length (as recorded in participant sleep restricted condition included getting to the diaries) did not differ significantly over the four laboratory.
During
the
sleep
restriction days preceding the start of data collection
condition, participants were woken by the (p=0.787; df=3, 18; F=0.352). This was an researcher
and
given
time
to
gather important outcome as it confirmed that, prior
themselves before completing the run. From to exposure to either experimental condition, the time of being woken up until termination of participants had obtained consistently good the
running
protocol,
participants
were sleep: on average, participants slept 441.4
exposed only to natural light, with no artificial (±57.2) minutes (±7hours 35 minutes) each light being used in the laboratory during night before data collection. Further analyses testing. Prior to each run, participants were revealed that the total reported sleep time fitted with a heart rate monitor and connected prior to the non-restricted sleep run did not to the ergospirometer. A 5-minute warm-up -1
differ significantly from the four days before
walk was permitted at 6km.hr . After this, the data collection (p=0.83; df=4, 24; F=0.352). treadmill speed was gradually increased to During
the
sleep
restriction
conditions,
the appropriate speed for each participant. perceived sleep durations averaged 227 (±10)
Data analysis All results were analysed using the Statistics software package, version 12 (Statistica,
minutes, which indicates that participants felt that they had slept for most of the four hours in the laboratory.
Statsoft, Inc.; Tulsa, Oklahoma, USA). A two
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differ significantly between the two conditions
Biomechanical responses
(p=0.39; df=1, 7; F=0.824) or over time There were no significant differences between (p=0.19; df=4, 28; F=1.633). Minute 1 was the experimental conditions with respect to excluded from the analyses as it reflected the stride length (p=0.388; df=1, 7; F=0.845). participants “getting up to speed” (Figure 1). Cadence (steps taken per minute) did not
Figure 1: A comparison of the mean stride -1
F=0.018) and energy expenditure (p=0.946;
length (m) and cadence (steps.min ) for both
df=1, 7; F=0.0048) at rest or during running.
sleep conditions over 5 minutes of the 6-
However, in both responses, there was a
minute submaximal running protocol.
significant increase in the transition from rest to exercise, with heart rate reaching a plateau
Physiological responses by the fifth minute, and energy expenditure There
were
no
significant
differences
observed between the two conditions with
reaching a plateau by the four minute (Figure 2).
respect to heart rate (p=0.896; df=1, 7;
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Figure 2: A comparison of mean heart rate
Perceptual responses did not differ between
(HR) and energy expenditure (EE) responses
conditions
for both sleep conditions over the 6-minute
F=0.342). However, there was a significant
submaximal running protocols.
increase in perceptual strain over the duration
Ratings of Perceived exertion
(Figure
3;
p=0.579;
df=1,
7;
of both runs (p
