Extremely short duration sprint interval training improves vascular health in older adults

Abstract

Exercise improves health and physical function in older people, but very few older people participate although the trend is for increasing participation. This study sought to determine whether short duration sprint interval training (SIT) improves health and physical function in older people. Seventeen (9 M and 8 F) older adults (age 66 ± 3 years) were recruited. Participants had blood pressure, physical function and blood lipid profile measured and were then allocated to a control group (CON n = 7) or a SIT group (n = 10). The control group maintained daily activities; the SIT group performed 10 weeks of twice-weekly training sessions of 6-s sprints. By week 10, training sessions lasted 11.6 ± 0.6-min. Ten weeks of SIT resulted in significant changes in pulse pressure (CONpre 59 ± 18 mmHg; CONpost 60 ± 9 mmHg; SITpre 56 ± 14 mmHg; SITpost 49 ± 7 mmHg; p = 0.007), mean blood pressure (CONpre 100 ± 10 mmHg; CONpost 97 ± 11 mmHg; SITpre 102 ± 7 mmHg; SITpost 93 ± 8 mmHg; p = 0.003), timed get up and go (CONpre 6.9 ± 1.1 s; CONpost 6.9 ± 1.0 s; SITpre 7.4 ± 1.2 s; SITpost 6.6 ± 1.0 s; p = 0.005), loaded 50 m walk (CONpre 6.9 ± 1.1 s; CONpost 6.9 ± 1.0 s; SITpre 7.4 ± 1.2 s; SITpost 6.6 ± 1.0 s; p = 0.005),and total cholesterol: HDL cholesterol ratio (CONpre 4.2 ± 0.7; CONpost 4.0 ± 0.7; SITpre 4.4 ± 1.1; SITpost 3.2 ± 0.7; p = 0.01). SIT is an effective way to maintain blood pressure, lipid profile, and physical function during aging and is an effective tool for promoting optimal aging.

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Sport Sciences for Health (2019) 15:123–131
https://doi.org/10.1007/s11332-018-0498-2
ORIGINAL ARTICLE
Extremely shortduration sprint interval training improves vascular
health inolder adults
SimonAdamson1· MykolasKavaliauskas2· TakakiYamagishi1· ShaunPhillips3· RossLorimer1· JohnBabraj1
Received: 18 December 2017 / Accepted: 1 September 2018 / Published online: 14 September 2018
© The Author(s) 2018
Abstract
Exercise improves health and physical function in older people, but very few older people participate although the trend is
for increasing participation. This study sought to determine whether short duration sprint interval training (SIT) improves
health and physical function in older people. Seventeen (9 M and 8 F) older adults (age 66 ± 3years) were recruited. Par-
ticipants had blood pressure, physical function and blood lipid profile measured and were then allocated to a control group
(CON n = 7) or a SIT group (n = 10). The control group maintained daily activities; the SIT group performed 10weeks of
twice-weekly training sessions of 6-s sprints. By week 10, training sessions lasted 11.6 ± 0.6-min. Ten weeks of SIT resulted
in significant changes in pulse pressure (CONpre 59 ± 18mmHg; CONpost 60 ± 9mmHg; SITpre 56 ± 14mmHg; SITpost
49 ± 7mmHg; p = 0.007), mean blood pressure (CONpre 100 ± 10mmHg; CONpost 97 ± 11mmHg; SITpre 102 ± 7mmHg;
SITpost 93 ± 8mmHg; p = 0.003), timed get up and go (CONpre 6.9 ± 1.1s; CONpost 6.9 ± 1.0s; SITpre 7.4 ± 1.2s; SITpost
6.6 ± 1.0s; p = 0.005), loaded 50m walk (CONpre 6.9 ± 1.1s; CONpost 6.9 ± 1.0s; SITpre 7.4 ± 1.2s; SITpost 6.6 ± 1.0s;
p = 0.005),and total cholesterol: HDL cholesterol ratio (CONpre 4.2 ± 0.7; CONpost 4.0 ± 0.7; SITpre 4.4 ± 1.1; SITpost
3.2 ± 0.7; p = 0.01). SIT is an effective way to maintain blood pressure, lipid profile, and physical function during aging and
is an effective tool for promoting optimal aging.
Keywords Aging· Sprint interval training· Blood pressure· Physical function
Introduction
Aging is associated with a reduction in cardiac and arterial
function with a marked increase in arterial stiffness, result-
ing in isolated systolic hypertension [1]. Pulse pressure is a
surrogate pulsatile component of blood pressure made up of
ventricular ejection, arterial stiffness and wave reflection [2].
At rest, ventricular ejection does not change over the lifespan
[3] and following 12months of endurance exercise ventricu-
lar ejection does not change at rest [4]. Therefore, it is sug-
gested that at rest pulse pressure represents either arterial
stiffness or wave reflection in older adults [2]. Furthermore,
arterial stiffening is a predictor for a number of vascular
diseases including heart failure, stroke and dementia [5].
Arterial stiffening is a predictor of vascular disease, but is
also strongly associated with the loss of physical function
and onset of functional limitations of old age [6].
The development of arterial stiffness has been linked to
both abnormal lipid and glucose metabolism [7]. However,
with age there is a decrease in glucose tolerance, result-
ing in increased fasting and post-prandial blood glucose
levels across the lifespan [8]. In addition, circulating total
cholesterol, low-density lipoprotein (LDL) cholesterol and
triglycerides concentrations can be elevated with age [9]
and are strongly associated with cardiovascular disease
risk [10]. Higher total cholesterol: high density lipopro-
tein (HDL) cholesterol ratios have been reported in older
adults with atherosclerotic alterations compared to those
with no atherosclerotic alterations [11]. The mechanisms
linking lipid profile to arterial stiffness are multifactorial,
including atherosclerosis, changes in the elastic elements
of the arterial wall, endothelial dysfunction and inflamma-
tion [12]. Following 12weeks of an aerobic and resistance
* John Babraj
j.babraj@abertay.ac.uk
1 Division ofSport andExercise Science, Abertay University,
DundeeDD11HG, Scotland,UK
2 School ofApplied Sciences, Sport, Exercise andHealth
Sciences, Edinburgh Napier University, Edinburgh, UK
3 Division ofSport andExercise Science, Edinburgh
University, Edinburgh, UK
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124 Sport Sciences for Health (2019) 15:123–131
1 3
exercise programme there is an improvement in systolic
blood pressure, pulse wave velocity and a reduction in
lipid profile in obese women [13]. Likewise, a 5-week
aerobic exercise programme has been shown to decrease
circulating triglycerides and glycosylated heamoglobin
(HbA1c) in older men [14]. Despite the benefits of aero-
bic and resistance exercise, the majority of older adults do
not take part in traditional exercise with time, dislike of
these exercise modes and risk of injury being barriers to
exercise participation [15].
Sprint interval training (SIT) can be a time-efficient
exercise paradigm but duration of SIT protocols can vary
between 10-min [16] and 30-min [17] depending on sprint
duration and recovery. Longer SIT protocols have typically
utilised 4–6 × 30-s sprints in a 1:8 work to rest interval on
3days per week and produce similar adaptations to tradi-
tional endurance training [18]. However, these protocols
last close to 30min. To overcome this number of recent
studies have looked at utilising 10-min protocols using
fewer sprints but still requiring a minimum of 3 training
days per week. Metcalfe etal. [19] demonstrated improved
VO2 max (13%) and insulin sensitivity (28%) in young
males when carrying out 2 × 20-s sprints. Gillen etal. [20]
demonstrate similar improvements in VO2 max (12%) in
young adults when using 3 × 20-s sprints at a lower resist-
ance and an 8% reduction in mean arterial pressure after
6weeks of training. Despite this reduction in total time,
the use of 20-s sprints may not be appropriate for older
adults due to the extended cardiovascular load, which is
similar to 30-s sprints in young adults [21]. Further, these
studies still require training to be carried out on 3days of
the week, which may limit people’s ability to follow these
protocols. In a middle-aged population, twice weekly SIT
sessions consisting of 6–10 × 6-s sprints, with a maximum
training duration of 10-min, has been shown to increase
VO2 peak (8%), decrease blood glucose area under the
curve (6%) and improve physical function [16]. Recently,
it has been demonstrated that a progressive SIT protocol
performed twice weekly over 6weeks will also improve
physical function and blood glucose control in older adults
[22]. However, the effectiveness of short sprints on blood
pressure components has not been investigated.
Longer duration sprints have been shown to improve
cardiovascular function and lower blood pressure in young
adults [18]. However, shorter duration sprints have been
shown to improve physical function and glucose metabo-
lism in older adults [22]. Therefore, the aim of this study
was to determine the effectiveness of a 10-week extremely
short duration SIT protocol (6-s) on blood pressure and
health in an older adult population. It was hypothesized
that SIT group would have improvements in physical func-
tion and resting blood pressure.
Materials andmethods
Participants
17 older adults (age range 60–71years) were recruited for
the study via local newspaper advertisement and were allo-
cated using a stratified approach to ensure that baseline age
was similar in the control group (CON: three males and
four females; Table1) or a twice per week SIT group (SIT:
four females, six males; Table1). More participants were
recruited to the SIT group to allow for potential dropout,
although dropout rate was zero. All participants were inac-
tive and participants were excluded if they had any metabolic
disease or cardiovascular disease. All participants had well-
controlled hypertension (blood pressure ≤ 160/90mmHg)
and were taking oral hypertensive medication which
remained unchanged for 6months prior to and during the
study. There was no significant difference in baseline char-
acteristics of the two groups (Table1), therefore, differences
in the group sizes do not bias the result [23]. Participants
allocated to the control group were asked to maintain their
normal lifestyle throughout the study period but took part
in no structured training. Participants allocated to the SIT
group took part in a twice weekly, 10-week SIT intervention,
but no other exercise training. All participants were asked
to report any changes in lifestyle or medication during the
study. All participants provided verbal and written informed
consent. The study had ethical approval from Abertay Uni-
versity Ethics Committee (SHS0701615) and conducted in
accordance with the declaration of Helsinki.
Baseline testing
Participant reported to the laboratory having fasted over-
night and height was recorded using a SECA 217 Stadi-
ometer (SECA United Kingdom, Birmingham, UK) and
weight determined using a SECA Medical 780 weighing
scales (SECA United Kingdom, Birmingham, UK).
Blood pressure
Prior to obtaining blood pressure measurements, all partici-
pants sat quietly for 5min with both arms in a forward posi-
tion, on a flat table surface. Blood pressure, pulse pressure
and mean arterial pressure was measured using a WatchBP
Office ABI Automatic Office Blood Pressure Measurement
Device (Microlife WatchBP AG, Widnau, Switzerland).
Triplicate blood pressure measurements were made, with a
1-min interval in-between, and the average value for blood
pressure, pulse pressure (pulse pressure = systolic − diastolic
pressure) and mean arterial pressure was recorded for both
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125Sport Sciences for Health (2019) 15:123–131
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left and right arms. It has been suggested that differences
in right and left arm blood pressure provides evidence of
peripheral vascular disease and is of clinical importance
[24].
Lipid profile
A finger prick blood sample was taken to allow measurement
of lipid profile. The initial blood droplet was discarded and
the second blood droplet taken for analysis of fasting lipid
levels (CardioChek PA, Polymer Technology Systems Inc,
Indianapolis, USA, within run CV for total cholesterol 4.7%,
HDL cholesterol 5.9% and triglyceride 4.3%). LDL choles-
terol was calculated using the modified Friedewald calcu-
lation (LDL-C (mgdl−1) = non-HDL-C × 90% − TG × 10%;
where TG = triglyceride, non-HDL-C = total-C − HDL-C)
[25].
Physical function [26]
Get up and go test: Participants began seated with their arms
folded across their chest. On the command go they rose from
the chair, without using their arms, and walked 6m, as fast
as possible without running, before sitting down on a chair.
This was repeated two times with the average time taken
reported.
Loaded 50m walk test: Participants were instructed
to walk 50m, as fast as possible without running, whilst
carrying 20% of their bodyweight for males and 15% of
their bodyweight for females. This was repeated two times
with the average time taken reported.
Step test: Participants were instructed to ascend the
nine stairs (each stair had a height of 16cm) as quickly as
they could. Power was calculated as the product of (total
vertical height of the stairs/time) × (body weight × 9.81).
SIT intervention
All SIT sessions were fully supervised and took place at
Abertay University. A bioharness 2 (Zephyr Technology,
Annapolis, USA) was attached to participants prior to the
training session to allow continuous recording of heart
rate (bpm) and breathing frequency. Participants then com-
pleted 6 × 6-s all-out effort cycle sprints, against 7% body-
weight for males and 6% bodyweight for females, with a
minimum of 60-s passive recovery or until heart rate was
below 120bpm. Passive recovery was chosen to allow the
heart rate to recover. The cycle sprint began once the par-
ticipant reached 100rpm. Each week one extra sprint was
added until the participants were completing ten sprints.
No warm-up or cool down was performed before or after
the session, with no adverse effects reported by any par-
ticipant. All participants completed 100% of the training
sessions. In week 1 training sessions averaged 8 ± 1.5min
and in week 10 training sessions averaged 11.6 ± 0.6min.
Table 1 Participant
characteristics, physical
function and circulating lipids
a p<0.05 SIT post versus control post
b p<0.01 SIT post versus control post
CONTROL SIT
Pre Post Pre Post
Participant characteristics
Age (years) 66 ± 2 66 ± 2 66 ± 4 66 ± 4
Height (cm) 164 ± 10 164 ± 10 169 ± 9 169 ± 9
Weight (kg) 70 ± 13 71 ± 13 77 ± 13 75 ± 12a
BMI (kgm−2)25.9 ± 3.3 26.2 ± 3.5 26.9 ± 3.5 26.3 ± 3.5
Blood measures
Total cholesterol (mmoll−1)4.8 ± 1.4 4.8 ± 1.2 5.8 ± 1.5 4.6 ± 1.3
HDL cholesterol (mmoll−1)1.1 ± 0.4 1.2 ± 0.3 1.4 ± 0.4 1.5 ± 0.4
LDL cholesterol (mmoll−1)3.0 ± 0.9 2.9 ± 1.0 3.6 ± 1.1 2.6 ± 1.1
Total triglyceride (mmoll−1)1.2 ± 0.6 1.3 ± 0.8 1.7 ± 1.0 1.2 ± 0.7
TC:HDL-C 4.2 ± 0.7 4.0 ± 0.7 4.4 ± 1.1 3.2 ± 0.7b
LDL:HDL-C 2.7 ± 0.6 2.4 ± 0.7 2.7 ± 0.9 1.7 ± 0.6a
TG:HDL-C 1.4 ± 1.0 0.9 ± 0.6 1.0 ± 0.3 1.1 ± 0.6
Physical function
Get up and go (s) 6.9 ± 1.1 6.9 ± 1.0 7.4 ± 1.2 6.6 ± 1.0b
Loaded 50m walk (s) 37.3 ± 4.3 36.8 ± 4.0 38.3 ± 4.8 34.9 ± 5.1b
Stair climb power (W) 208 ± 86 200 ± 98 253 ± 46 285 ± 59a
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126 Sport Sciences for Health (2019) 15:123–131
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Post‑testing
All tests were repeated at the same time of day, with the
same fast period and in the same order as baseline after
10weeks. There was 5 ± 2days between last training ses-
sion and retesting of participants. This was to ensure that a
training effect has being measured rather than a response to
the last training session.
Data andstatistical analysis
Heart rate area under the curve for the first 6 sprints in train-
ing session 1 and training session 20 was calculated using
the trapezoidal rule. Statistical analysis was carried out using
SPSS version 23. All data were checked for normal distribu-
tion using a Shapiro–Wilk test and was within normal values
for skewness and kurtosis. Independent samples t test was
used to determine the differences in baseline characteris-
tics between the groups. Effects of training on each variable
were analysed using an ANCOVA to determine difference
between groups. A one way repeated measures ANOVA was
used to analyse the heart rate area under the curve and aver-
age power data from training session 1 and training session
20. Significance was accepted as p < 0.05. Partial eta squared
(η2) was defined as 0.02 small, 0.13 medium and 0.26 large
as proposed by Bakeman [27]. A Pearson’s correlation was
carried out between dependent variables.
Results
Blood pressure changes
There were no significant differences in blood pressure
variables between the control and SIT group at baseline or
between right and left arm blood pressure measures (Fig.1).
Following 10weeks of SIT, there was a significant reduc-
tion compared to control for both right and left arm sys-
tolic blood pressure (right arm: p < 0.01, η2 = 0.54; left arm:
p < 0.01, η2 = 0.61; Fig.1); right and left arm diastolic blood
pressure (right arm: p = 0.05, η2 = 0.24; lef t arm: p = 0.02,
η2 = 0.33; Fig.1); right and left arm pulse pressure (right
arm: p < 0.01, η2 = 0.55; left arm: p < 0.01, η2 = 0.53; Fig.1);
right and left arm mean arterial pressure (right arm: p = 0.01,
η2 = 0.37; left arm: p < 0.01, η2 = 0.49; Fig.1). Sex responses
are shown in Table2.
Fig. 1 Changes in vascular measures; a right arm systolic and diastolic blood pressure; b left arm systolic and diastolic blood pressure; c right
arm pulse pressure and mean arterial pressure; d left arm pulse pressure and mean arterial pressure. *p < 0.05 SIT post versus control post
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127Sport Sciences for Health (2019) 15:123–131
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Heart rate area underthecurve
There was no significant sprint × time interaction for aver-
age power (p = 0.358) between session 1 and session 20
(Fig.2). There was a significant sprint × time interaction
(p = 0.048, η2 = 0.17) for heart rate area under the curve
(Fig.2). Following 10weeks of SIT, heart rate AUC aver-
aged across the first six sprints of a SIT session was sig-
nificantly reduced (session 1: 6994 ± 372beatsmin−1s−1;
session 20: 6426 ± 153beatsmin−1s−1; p < 0.01). There
were no significant differences between the sessions for
sprints 1 and 2 (p > 0.05), however, there was a signifi-
cant difference between sessions for sprints 3, 4, 5 and 6
(p < 0.05, Fig.2).
Physical function
There were no significant differences in physical func-
tion between the control and SIT group at baseline
(Table1). Following 10weeks of SIT, there was a sig-
nificant improvement in physical function compared to
the control group (get up and go: p = 0.01, η2 = 0.44;
loaded 50m walk: p < 0.01, η2 = 0.50; stair climb power:
p = 0.04, η2 = 0.26; Table1). There is a significant corre-
lation between the change in pulse pressure and change in
get up and go (R = 0.55; p = 0.023) and loaded 50m walk
(R = 0.50; p = 0.041) but not with change in mean arterial
pressure (p > 0.05) or change in systolic blood pressure
(p > 0.05). Sex responses are shown in Table2.
Blood measures
There were no significant differences in blood measures
between the control and SIT group at baseline (Table1).
Following 10weeks of SIT, Total Cholesterol/HDL cho-
lesterol (p = 0.01, η2 = 0.42) and LDL cholesterol/HDL
cholesterol (p = 0.02, η2 = 0.34) were significantly reduced
compared to the control group (Table1). There was a trend
for reduction in total cholesterol (p = 0.07, η2 = 0.23), triglyc-
eride (p = 0.06, η2 = 0.24) and triglyceride/HDL cholesterol
(p = 0.06, η2 = 0.24; Table1).
Discussion
The major finding from this study is that training twice
weekly, with each session lasting no longer than 12-min,
is sufficient to improve resting blood pressure and physi-
cal function in older adults. This demonstrates that reduc-
ing the training frequency does not impede adaptation to
sprint interval training in older adults. It could be pos-
sible that a further reduction in training frequency could
still promote health benefits in an older population. This
could have major implications as to how we encourage
older adults to exercise. It would appear that fewer train-
ing sessions are required than is currently recommended
for health benefits [20]. In the current study, there was
a significant reduction in left and right arm systolic and
diastolic blood pressure, pulse pressure and mean arterial
Table 2 Male and Female data
for blood pressure components
and physical function
R right arm, L left arm, BP blood pressure, Sys systolic, Dia diastolic, PP pulse pressure, MAP mean arte-
rial pressure, GUAG get up and go, L50m loaded 50m walk
SIT pre SIT post CONTROL pre CONTROL post
M (n = 6) F (n = 4) M (n = 6) F (n = 4) M (n = 3) F (n = 4) M (n = 3) F (n = 4)
BP (mmHg)
R Sys 136 ± 13 141 ± 13 122 ± 9 131 ± 6 137 ± 4 138 ± 13 149 ± 9 135 ± 6
R Dia 85 ± 5 85 ± 5 77 ± 9 84 ± 4 82 ± 9 76 ± 8 87 ± 5 74 ± 6
L Sys 138 ± 14 137 ± 15 122 ± 11 131 ± 7 137 ± 6 135 ± 15 146 ± 4 137 ± 7
R Sys 84 ± 5 82 ± 7 77 ± 7 78 ± 11 81 ± 9 75 ± 9 87 ± 7 74 ± 7
PP (mmHg)
Right 53 ± 8 56 ± 13 45 ± 6 54 ± 14 54 ± 4 60 ± 15 62 ± 3 62 ± 13
Left 57 ± 14 55 ± 14 48 ± 5 52 ± 10 55 ± 5 61 ± 15 59 ± 6 61 ± 11
MAP (mmHg)
Right 104 ± 9 94 ± 8 94 ± 10 88 ± 11 96 ± 4 86 ± 12 106 ± 5 96 ± 9
Left 104 ± 8 93 ± 7 94 ± 8 87 ± 12 94 ± 7 83 ± 11 104 ± 7 90 ± 8
GUAG (s) 8.0 ± 1.2 6.5 ± 0.6 7.0 ± 1.1 5.9 ± 0.4 6.4 ± 1.2 7.2 ± 1.2 6.7 ± 1.6 7.0 ± 0.6
L50m (s) 39 ± 5 36 ± 4 36 ± 6 33 ± 3 35 ± 4 39 ± 4 34 ± 4 39 ± 3
Power (W) 269 ± 54 229 ± 13 317 ± 56 236 ± 10 272 ± 99 159 ± 19 264 ± 99 152 ± 21
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128 Sport Sciences for Health (2019) 15:123–131
1 3
pressure in older adults after 10 weeks of training. We
also demonstrate an improved heart rate recovery in older
adults when performing repeated sprint exercise. Further,
we also demonstrate that 10-week sprint interval train-
ing lowers circulating lipid profile in older adults. This
suggests that SIT could be a useful exercise paradigm to
reduce cardiovascular disease risk in older adults.
Blood pressure changes
Systolic blood pressure (7%), diastolic blood pressure (9%),
pulse pressure (9%) and mean arterial pressure (8%) were
all significantly reduced with a medium to large effect size
(η2 ≥ 0.24 for all measures; Fig.1) following twice weekly
SIT. In normotensive young men and women longer duration
intervals performed on 3days per week have been shown to
reduce systolic and diastolic blood pressure by 2–7% and
mean arterial pressure by 6% [20, 28]. Given our findings
are of a similar magnitude, even though total weekly dura-
tion is much lower, then this suggests that the duration of the
sprint is not a driving factor in blood pressure adaptation to
SIT. Ejection fraction does not appear to change with either
endurance training [4] or with 30-s repeated high intensity
bursts [29] and resting heart rate was unchanged in this study
(data not reported). It could be speculated that improve-
ments in pulse pressure at rest, reported in this study, reflect
changes in arterial stiffness or wave reflection. The reduction
in MAP (8%) is similar to that seen in obese adults (6%)
after 2-week of 4–6 30-s sprints [30], but greater than that
reported in young people following 1–6 30-s sprints [31].
Obesity like ageing is associated with an increase in total
peripheral resistance that may reflect endothelial dysfunc-
tion [32]. Therefore, the reduction in mean arterial pressure
may reflect improved endothelial function seen in other SIT
protocols [31]. Given that hypertension is the most common
risk factor for cardiovascular morbidity and mortality across
the lifespan [33], then twice-weekly 6-s SIT is an effective
intervention to lower hypertension risk in older adults.
Heart rate area underthecurve
Following 10weeks of SIT, heart rate AUC during sprints
and recovery was significantly reduced by 8% (Fig.2). This
reduction in heart rate AUC occurs despite the average
power produced across the six sprints being similar (Fig.2).
This reduction in heart rate AUC following SIT could be
related to altered autonomic function. Short duration sprints
(8s sprint with 12s recovery over 20min) have been shown
to alter autonomic control of the heart via greater vagal
influence on heart rate at rest in young overweight women
[34]. When looking at the individual heart rate trace there
is a reduction in peak heart rate following each sprint, with
a more rapid recovery after exercise (Fig.2). This suggests
that there is either lower sympathetic activity post training
or withdrawal of vagal tone [35] during each sprint result-
ing in a lower heart rate response. Given that HR recovery
is associated with several pathophysiological abnormalities
and is considered as an independent risk factor for the devel-
opment of cardiovascular disease [33] these findings may
have important clinical implications for older adults.
Fig. 2 Changes in heart rate during training; a average power across
the first six sprints; b heart rate area under the curve for each sprint
and recovery period; c example trace of heart rate across 6 sprints.
*p < 0.05 session 1 compared to session 20
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129Sport Sciences for Health (2019) 15:123–131
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Lipid profile
The ratio of total cholesterol/HDL cholesterol (26%) and LDL
cholesterol/HDL cholesterol (33%) were significantly reduced
compared to control (Table2) following SIT, with a strong
trend for reduction of circulating total cholesterol (19%) and
triglyceride levels (23%; Table2). The magnitude of change
is similar to that reported in older adults following a 3 times
per week endurance programme lasting 50min per session
[36] and a treadmill-based sprint protocol in inactive females,
consisting of 10 × 15s sprints with 30s rest on 3days per week
[37]. However, SIT was only performed on 2days per week
compared to the 3days per week in endurance and run-based
high intensity with a much lower total sprint time. This may
reflect increased clearance of lipids from the blood or reduced
secretion of lipids from the liver. Fat oxidation has been shown
to be increased following longer duration SIT protocols [38]
and VLDL secretion has been shown to be reduced following
long duration (4min intervals) high intensity training [39].
However, this remains to be determined with this short sprint
protocol.
Physical function
Following 10weeks of twice per week SIT, there was a sig-
nificant improvement in get up and go (11%), loaded 50m
walk (9%) and stair climb power (dpcc2 ≥ − 0.8 for all meas-
ures Table2). In older adults, a 10-week endurance training
programme, carried out 3days per week for 50min, resulted
in a 15% reduction in 1 mile walk [36]. Likewise, a 14-week
progressive resistance training programme improved timed get
up and go by 15% [40]. The improvements in physical func-
tion are similar to those reported after 6 weeks of 6s SIT, 7%
improvement in loaded 50m walk, 7% improvement in get up
and go [22], suggesting that improvements in physical func-
tion occur early during SIT but continue to improve as train-
ing progresses. There is a significant correlation between the
change in resting pulse pressure and the change in loaded 50m
walk (R = 0.5; p = 0.04) and get up and go (R = 0.55; p = 0.02).
This is similar to the correlation reported for improvements in
arterial stiffness and physical function with endurance exercise
[6]. Given at rest in the elderly, pulse pressure reflects either
arterial stiffness or wave amplification then this suggests that
changes within the blood vessel structure are important for
physical function adaptations following SIT. Further these
adaptations are seen within only twice weekly training ses-
sions lasting approximately 10min.
Conclusion
In this study, we show for the first time the adaptation
in blood pressure and physical function in older adults
to a twice-weekly extremely short duration SIT. These
results should be considered in context of the limitations
of the study and future studies should look to record all
medication being taken by participants and seek to record
daily activity and nutritional intake across the intervention
period. However, there are significant improvements in
vascular and physical function and these improvements in
physical function are strongly correlated to the improve-
ments in pulse pressure (R = 0.55), which may reflect
greater arterial compliance following SIT. Given that one
of time and dislike of traditional exercise are barriers to
participation [20] then there is a need to reappraise current
exercise advice for older adults to do 150min of moderate
or 75min of vigorous intensity exercise a week [41]. The
current study has a much lower time commitment but more
research is required to determine minimum effective train-
ing load of SIT to promote optimal aging in older adults.
Acknowledgements This project was supported by Abertay University.
Compliance with ethical standards
Conflict of interest The authors declare no conflict of interest.
Ethical approval The study was granted ethical approval by the insti-
tutional ethics committee (SHS0701615) and was carried out in line
with the Declaration of Helsinki (World Medical Association 2013).
Informed consent All participants were given verbal and written infor-
mation about the study prior to providing informed consent.
Open Access This article is distributed under the terms of the Crea-
tive Commons Attribution 4.0 International License (http://creat iveco
mmons .org/licen ses/by/4.0/), which permits unrestricted use, distribu-
tion, and reproduction in any medium, provided you give appropriate
credit to the original author(s) and the source, provide a link to the
Creative Commons license, and indicate if changes were made.
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