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Background and aim: Exercise training regimes can lead to improvements in measures of cardiorespiratory fitness (CRF), improved general health, and reduced morbidity and overall mortality risk. High-intensity interval training (HIIT) offers a time-efficient approach to improve CRF in healthy individuals, but the relative benefits of HIIT compared with traditional training methods are unknown in across different disease cohorts. Methods: This systematic review and meta-analysis compares CRF gains in randomized controlled trials of short-term (<8 wk) HIIT versus either no exercise control (CON) or moderate continuous training (MCT) within diseased cohorts. Literature searches of the following databases were performed: MEDLINE, EMBASE, CINAHL, AMED, and PubMed (all from inception to December 1, 2017), with further searches of and citations via Google Scholar. Primary outcomes were effect on CRF variables: V˙O2peak and anaerobic threshold. Results: Thirty-nine studies met the inclusion criteria. HIIT resulted in a clinically significant increase in V˙O2peak compared with CON (mean difference [MD] = 3.32 mL·kg·min, 95% confidence interval [CI] = 2.56-2.08). Overall HIIT provided added benefit to V˙O2peak over MCT (MD = 0.79 mL·kg·min, 95% CI = 0.20-1.39). The benefit of HIIT was most marked in patients with cardiovascular disease when compared with MCT (V˙O2peak: MD = 1.66 mL·kg·min, 95% CI = 0.60-2.73; anaerobic threshold: MD = 1.61 mL·kg·min, 95% CI = 0.33-2.90). Conclusions: HIIT elicits improvements in objective measures of CRF within 8 wk in diseased cohorts compared with no intervention. When compared with MCT, HIIT imparts statistically significant additional improvements in measures of CRF, with clinically important additional improvements in V˙O2peak in cardiovascular patients. Comparative efficacy of HIIT versus MCT combined with an often reduced time commitment may warrant HIIT's promotion as a viable clinical exercise intervention.
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Short-Term (G8 wk) High-Intensity Interval
Training in Diseased Cohorts
University of Nottingham, Nottingham, UNITED KINGDOM; and
Royal Derby Hospital, Derby, UNITED KINGDOM
Term (G8 wk) High-Intensity Interval Training in Diseased Cohorts. Med. Sci. Sports Exerc., Vol. 50, No. 9, pp. 1740–1749, 2018.
Background and Aim: Exercise training regimes can lead to improvements in measures of cardiorespiratory fitness (CRF), improved
general health, and reduced morbidity and overall mortality risk. High-intensity interval training (HIIT) offers a time-efficient ap-
proach to improve CRF in healthy individuals, but the relative benefits of HIIT compared with traditional training methods are
unknown in across different disease cohorts. Methods: This systematic review and meta-analysis compares CRF gains in randomized
controlled trials of short-term (G8 wk) HIIT versus either no exercise control (CON) or moderate continuous training (MCT) within
diseased cohorts. Literature searches of the following databases were performed: MEDLINE, EMBASE, CINAHL, AMED, and
PubMed (all from inception to December 1, 2017), with further searches of and citations via Google Scholar.
Primary outcomes were effect on CRF variables: V
and anaerobic threshold. Results: Thirty-nine studies met the inclusion criteria.
HIIT resulted in a clinically significant increase in V
compared with CON (mean difference [MD] = 3.32 mLIkg
confidence interval [CI] = 2.56–2.08). Overall HIIT provided added benefit to V
over MCT (MD = 0.79 mLIkg
, 95% CI =
0.20–1.39). The benefit of HIIT was most marked in patients with cardiovascular disease when compared with MCT (V
1.66 mLIkg
, 95% CI = 0.60–2.73; anaerobic threshold: MD = 1.61 mLIkg
, 95% CI = 0.33–2.90). Conclusions: HIIT
elicits improvements in objective measures of CRF within 8 wk in diseased cohorts compared with no intervention. When compared
with MCT, HIIT imparts statistically significant additional improvements in measures of CRF, with clinically important additional
improvements in V
in cardiovascular patients. Comparative efficacy of HIIT versus MCT combined with an often reduced time
commitment may warrant HIIT_s promotion as a viable clinical exercise intervention. Key Words: HIIT, V
Objective measures of cardiorespiratory fitness (CRF)
(e.g., V
and anaerobic threshold [AT]) predict
whole-body health, morbidity, and mortality (1–4).
These measures of CRF can be altered via participation in
exercise training regimens, which in turn may improve
general health. Traditionally, endurance-based aerobic activ-
ity or ‘‘moderate continuous training’ (MCT) has been used
to improve CRF (5) and exercise tolerance (6).
Despite MCT (150 min of moderate aerobic activity every
week) forming the primary basis of almost all public health
exercise-based recommendations (7,8), greater attention has
recently been paid to the utility of higher intensity exercise
(75 min of vigorous activity every week) as an alternative to
MCT (7) in the context of ‘‘exercise for health’’ (9) as the latter
is more time efficient, which may improve compliance (10).
Patients can have modification of disease risk factors through
exercise interventions (e.g., reduction of blood pressure in
those at risk of stroke) (11), and exercise can also be used to
help optimize patients before a planned intervention (e.g.,
patients with suspected cancer or those awaiting urgent elec-
tive surgery for malignancy) (12). For those having major
surgical procedures, perioperative outcome is in large part
dependent on preoperative CRF (2). An ability to rapidly
improve CRF would therefore be attractive if deliverable in
the short time available between the suspicion of cancer and
initiation of primary treatment (13).
Often however, there is not an extended period available
from clinical suspicion of cancer before first definitive
Address for correspondence: James Blackwell, B.M.B.S., B.Sc., Graduate Entry
Medicine Building, University of Nottingham, Royal Derby Hospital, Room
5032, Uttoxeter New Road, Derby DE22 3NE; E-mail:
Submitted for publication December 2017.
Accepted for publication March 2018.
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Copyright Ó2018 The Author(s). Published by Wolters Kluwer Health, Inc.
on behalf of the American College of Sports Medicine. This is an open-
access article distributed under the terms of the Creative Commons
Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-
ND), where it is permissible to download and share the work provided it
is properly cited. The work cannot be changed in any way or used com-
mercially without permission from the journal.
DOI: 10.1249/MSS.0000000000001634
treatment to complete exercise programs: for example, in the
United Kingdom, the National Cancer Action Team imposes
two cancer waiting time service standards (13). The first is a
62-d target from initial GP referral for suspected cancer or
urgent referral from NHS screening program, whereas the
second is a 31-d window from the decision to treat to primary
treatment (surgery, drug treatment, or radiotherapy) of the
cancer (13). These standards have led to increasing interest in
novel exercise interventions to improve CRF within truncated
time frames. It has been suggested that exercise regimens such
as high-intensity interval training (HIIT) may deliver clinically
important improvements in CRF within a clinically relevant
time frame with minimal time commitment from the patient.
HIIT, defined as brief intermittent bursts of vigorous activity
interspersed with periods of rest or low-intensity exercise (14),
can bring more pronounced improvements in objective mea-
sures of CRF than MCT in healthy individuals over an
equivalent number of weeks (15). It is unknown whether in-
dividuals with disease will benefit from HIIT in the same way.
In any exercise intervention, it is essential that there are high
levels of adherence and compliance to maximize benefit, es-
pecially given that comorbid patients have been shown to be
poor compliers with exercise interventions (16). HIIT has
previously been reported to be more enjoyable than MCT (17).
Time pressure has been identified as one of the most com-
monly cited barriers to exercise adherence (10,18). HIIT_s
reduced time commitment and training volume makes it an
attractive option for rapidly achieving maximal gains in CRF.
Previous reviews in distinct disease groups exploring the
efficacy of HIIT over longer time durations (median 12 wk)
have reported benefits of HIIT over MCT in cardiometabolic
disease (19) and possible improved efficacy in patients with
chronic obstructive pulmonary disease (20). However, equal
effects on CRF have been seen in HIIT and MCT in patients
with coronary artery disease during cardiac rehabilitation
(21). In general, within disease groups, 8–16 wk exercise
programs involving HIIT have been shown to be as effective
as MCT(22), whereas uncontrolled studies have shown large
increases in CRF following HIIT across comorbidities as
varied as cardiac disease (23), diabetes (24), obesity (25),
and asthma (26). HIIT retains the advantage of requiring
significantly less time commitment than MCT.
The aim of this review was to compare the effect of HIIT
to no exercise control (CON) or MCT on CRF (V
in differing disease states over short time frames (e8 wk).
We also aimed to identify conditions where HIIT might be
particularly effective compared with CON or MCT.
Study design. This systematic review was prospectively
registered with PROSPERO (registration no. CRD42016042299)
and performed according to the PRISMA statement (27). Only
randomized control trials evaluating HIIT versus CON or
HIIT versus MCT were included. Other inclusion criteria were
participants 917 yr old with disease, an intervention duration
of 8 wk or less, and trials where outcome data were reported
pre- and postintervention. Trials involving a drug treatment or
dietary supplementation were excluded. We classified trials as
delivering HIIT if they satisfied the following criteria: (i) high-
intensity efforts interspersed with reduced or noeffort recovery
periods, (ii) high-intensity bouts 985% predicted heart rate or
heart rate reserve, or (iii) high-intensity bouts 985% of peak
power output or peak power achieved at baseline exercise test.
Studies using ‘supramaximal’’ loading of 9100% wattage max
at cardiopulmonary exercise testing or similar loading criteria
were not included.
Literature search. Literature searches were conducted
by a research team member (BD) using the following databases:
searched from their inception to December 1, 2017, with no
language restriction. A detailed search for unpublished studies
was conducted on The Cochrane library of
systematic reviews was searched for relevant previous reviews,
and previous systematic reviews of related topics were also
searched for relevant primary studies. References of all identified
potentially relevant primary studies were hand searched for further
relevant studies. Finally, we searched for studies citing the iden-
tified potentially relevant primary studies on Google Scholar to
identify any further work potentially meeting the inclusion criteria.
Medical subject headings (MeSH) included the terms
‘HIIT,’’ ‘‘HIT,’’ and ‘‘EXERCISE.’’ Free-text words included
‘exercise,’’ ‘‘high AND intensity,’ and ‘‘interval.’’ Abstracts
of identified studies were screened by two authors indepen-
dently (JB and BD). Full text versions of potentially relevant
primary studies were then independently screened against the
inclusion and exclusion criteria by two authors (JB and SR)
and agreement to inclusion reached by consensus.
Data extraction. Study characteristics (authors and year
of publication, mean age [yr], % female individuals, training
intervention duration (wk), number of planned exercise ses-
sions in total, disease state, individual exercise protocols, and
country of origin) were extracted by one author (JB) with
outcome data (V
, AT, systolic blood pressure [SBP],
diastolic blood pressure [DBP], 6-MWT, quality of life [QoL]
questionnaires, and adherence data) independently extracted
and verified by two authors (JB and SR). Risk of bias for
included studies was assessed using the Cochrane Collabora-
tion tool for assessing risk of bias. This was performed inde-
pendently by two authors (JB and BD), with any disagreement
resolved by consensus with a third party author (PH). When
outcome data were only reported in graphical form, data were
extracted using WebPlotDigitizer (Version 3.12, Austin, TX).
Statistical analysis. To facilitate meta-analysis of change
variables when SD values of change were not reported, SD
values were imputed using recommended methods described
in the Cochrane Handbook (28). First, studies that reported
data as SD of the difference between pre- versus postvalues
were used to calculate correlation coefficients; these were
then averaged for each outcome and used these to calculate
change SD from reported baseline and final SD. Outcomes
were aggregated using a random-effects model. Changes in
SHORT-TERM HIIT IN COMORBIDITY Medicine & Science in Sports & Exercise
and AT are presented as mean difference (MD) with
95% confidence intervals (CI) in milliliters per kilogram per
minute. All other continuous outcomes are also reported as
MD. Minimal clinically significant improvements were defined
as follows: change in V
and AT 91.5 mLIkg
(12), 6-min walk test (6-MWT) 917–23 m (29,30), and SBP/
DBP of G10 mm Hg/5 mm Hg (11).
The I
statistic was used to quantify statistical heteroge-
neity, with values above 50% taken as evidence of statistical
heterogeneity. Publication bias was assessed qualitatively
using funnel plots and quantitatively using Egger_s linear
regression test (PG0.05 as evidence of imprecise study ef-
fects). We investigated heterogeneity using a random-effects
restricted maximum likelihood meta-regression. Covariates
included mean age of participants, duration of intervention
(wk), and disease cohort. For disease cohorts, we created
dummy variables and used the least effective subgroup as
the reference category. We report the between-study het-
erogeneity explained by the model (R
analog) with a cor-
responding Pvalue. The Knapp–Hartung modification was
used as the variance estimator. To assess the quality of
evidence, the GRADE approach (28) was used with evi-
dence downgraded to moderate, low, or very low quality
owing to concerns over unexplained heterogeneity, indi-
rectness of evidence, possible publication bias, imprecision
in effect estimates, and concerns over risk of bias. All cal-
culations were conducted using STATA 15 (StataCorp,
College Station, TX).
Search Results
A total of 2612 abstracts were screened for inclusion,
2570 from the initial literature search and 42 from the ref-
erence lists of other identified studies, Google Scholar cita-
tions, and other systematic reviews. Of the 2612 abstracts
screened, 2559 were excluded as not being relevant or dupli-
cates, leaving 53 studies for full-text review. Of the 53 studies
undergoing full text review, 14 were excluded, leaving 39
studies for inclusion in the qualitative analysis and 34 studies
for quantitative analysis (Fig. 1, PRISMA Flow Chart [27])
FIGURE 1—PRISMA flow diagram.
http://www.acsm-msse.org1742 Official Journal of the American College of Sports Medicine
Study Characteristics
The characteristics of the included studies can be found in
the online supplementary tables (See Tables, Supplemental
Digital Content 1,, Paper
Characteristics, HIIT vs CON and Supplemental Digital
Content 2,, Paper Char-
acteristics, HIIT vs MCT). The earliest study meeting the
inclusion criteria was published in 1999 and the latest in
2016. All studies were published as journal articles. The
interventions studied were HIIT versus CON or HIIT versus
MCT. Three studies were included in both analyses which
compared HIIT versus CON versus MCT (37,38,64).
Risk of Bias
All included studies were at high risk of bias in at least
one domain (see Figure, Supplemental Digital Content 3,, which shows risk of bias
summary chart). The majority of studies were at high risk of
bias due to the innate difficulties in blinding participants to a
physical activity intervention. A large number of studies did
not describe their random sequence allocation or allocation
concealment in sufficient detail to be judged as low risk of
bias, and many did not describe blinding of their outcome
assessment. Many studies were at risk of reporting bias and
some may have suffered from attrition bias.
Data Synthesis
There were sufficient studies to perform independent
meta-analysis for V
, AT, SBP, and DBP for both HIIT
versus CON and HIIT versus MCT interventions.
.Of 11 study groups from 11 trials analyzed for
the comparison of HIIT versus CON, comprising 153 in-
dividuals in the HIIT groups and 124 CON participants,
HIIT produced a clinically significant increase in V
compared with CON (MD = 3.38 mLIkg
, 95%
CI = 2.7–4.05, I
= 47.8%) (Fig. 2). Of 25 study groups
from 24 trials comparing HIIT to MCT, comprising 359
individuals in the HIIT groups and 341 MCT participants,
HIIT provided additional mean increase in V
pared with MCT (MD = 0.79 mLIkg
, 95% CI =
0.20–1.39, I
= 50.5%) (Fig. 3). However, this improve-
ment did not meet our a priori target of clinical significance
(91.5 mLIkg
). Cardiovascular patients showed the
greatest improvement, with clinically significant mean increases
in V
following HIIT (MD = 1.66 mLIkg
0.60–2.73, I
On meta-regression analysis, duration of intervention showed
significance for HIIT versus CON (R
=53.0%,P= 0.04) but
nonsignificant for HIIT versus MCT (R
For HIIT versus CON, longer duration of interventions led to
larger increases in V
. Neither HIIT versus CON nor HIIT
versus MCT showed significant interaction for age (R
FIGURE 2—Forest plot showing meta-analysis of V
data for HIIT vs CON (WMD mLIkg
). Diamonds to the right of the plot show
benefit with HIIT.
SHORT-TERM HIIT IN COMORBIDITY Medicine & Science in Sports & Exercise
P= 0.637 and R
=0%,P= 0.529, respectively). On
meta-regression analysis of HIIT versus MCT, HIIT was more
effective in cardiovascular patients (R
than respiratory patients.
There was no evidence of publication bias in either anal-
ysis (P=0.16andP= 0.91). The quality of evidence of V
data was regarded as moderate for HIIT versus CON
(downgraded owing to concerns over risk of bias) and low for
HIIT versus MCT (downgraded owing to concerns over risk of
bias and unexplained heterogeneity) using GRADE criteria (65).
AT. A single study reported AT after HIIT versus CON,
showing a mean improvement in AT after HIIT versus CON
(MD = 1.5 mLIkg
, 95% CI = 0.18–2.82). There was
no further data available for meta-analysis to be performed in
relation to AT for HIIT versus CON.
HIIT provided additional increase in AT compared with
MCT of borderline statistical but not clinical significance
(MD = 1.26 mLIkg
, 95% CI = j0.02 to 2.54, I
38.3%) in six study groups from five trials, comprising 84
individuals receiving HIIT and 79 MCT. Cardiovascular
patients showed the greatest mean improvement in AT after
HIIT in comparison with MCT (MD = 1.61 mLIkg
95% CI = 0.33–2.90, I
= 39.8%) (Fig. 4). The quality of
evidence of AT data for HIIT versus MCT was regarded as
low using GRADE criteria (downgraded owing to concerns
over risk of bias and imprecision) (65).
6-MWT. A single study reported 6-MWT outcomes for
HIIT versus CON with an effect size of 66 m after HIIT (P=
0.001) (66). For the comparison of HIIT versus MCT, six
study groups from 6 trials were analyzed, comprising 151
individuals in the HIIT groups and 149 participants in the
MCT group. HIIT delivered an increase in 6-MWT distance
compared with MCT (MD = 11.67 m, 95% CI = 1.28–22.06,
= 38.9%). Cardiovascular patients showed a greater, yet
clinically insignificant improvement (MD = 16.64 m, 95%
CI = 5.22–28.07, I
= 31.9%) compared with respiratory
patients (MD = 2.05 m, 95% CI = j12.57 to 16.66, I
The quality of evidence 6-MWT was regarded as low using
GRADE criteria (downgraded owing to concerns over risk
of bias and imprecision) (65).
Blood pressure. When analyzing blood pressure changes
in HIIT versus CON, six study groups from six trials reported
SBP results, whereas only five trials presented data for analysis
of DBP changes due to unreliable data in one study (47). These
studies comprised 79 individuals for SBP in the HIIT groups
(DBP 66 individuals) and 67 individuals for SBP in the CON
groups (DBP 57 individuals). Compared with CON, HIIT
provided a nonsignificant reduction in SBP (MD = j4.48 mm
Hg, 95% CI = j11.13 to 2.18, I
= 58.8%) and a statistically
significant reduction in DBP (MD = j3.05 mm Hg, 95% CI =
j5.41 to j0.69, I
= 0%), which however did not meet our
aprioritarget of clinical significance (DBP, 5 mm Hg).
FIGURE 3—Forest plot showing meta-analysis of V
data for HIIT vs MCT (WMD mLIkg
). Diamonds to the right of the plot show
benefit with HIIT.
http://www.acsm-msse.org1744 Official Journal of the American College of Sports Medicine
When analyzing BP changes in HIIT versus MCT, for SBP
and DBP, eight study groups from eight trials were included.
These studies comprised 116 individuals for both SBP and
DBP in the HIIT groups and 113 individuals for SBP and DBP
in the CON groups. HIIT provided no additional benefit in
either SBP (MD = 0.48 mm Hg, 95% CI = j2.01 to 2.97, I
0.0%) or DBP (MD = j0.51 mm Hg, 95% CI = j2.53 to
1.50, P=0.136,I
= 36.8%) compared with MCT. The quality
of evidence for blood pressure was regardedas moderate to low
using GRADE criteria (downgraded owing to concerns over
risk of bias and imprecision for some analyses) (65).
QoL. There was marked variation in both instrument
selection and reporting of QoL qualitative measures, and
questionnaire outcomes were equivocal between both HIIT
versus CON and HIIT versus MCT (see Tables, Supple-
mental Digital Content 4,,
HIIT versus CON, and Supplemental Digital Content 5,, HIIT vs MCT, which shows
QoL questionnaire outcomes). The most commonly reported
QoL questionnaire was SF-36 (67). Studies including SF-36
data did so either with a total score (overall scores) or by
domains (summary scores) of the full questionnaire (i.e.,
Physical Health, Perceived Health, Mental Health). Dunne
et al. (12) reported that HIIT prehabilitation was associated
with improvements in overall SF-36 QoL and SF-36 mental
health scores (change of +11 P=0.028and+11P=0.037,
respectively). Gloeckl et al. (43) reported increased overall
SF-36 scores after both HIIT and MCT; however, only the
physical health summary score in the MCT group (MD = 4.3
PG0.05) and the mental health summary score in the HIIT
group (MD = 9.7 PG0.05) improved significantly. Freese
et al. (41) reported clinically meaningful improvements in
role–physical scores, bodily pain, vitality, social functioning,
mental health, and total SF-36 score after 6 wk HIIT.
Jaureguizar et al. (48) reported significant increases in the
role emotional, mental health, self-reported health status,
and mental health index after HIIT only. Other QoL ques-
tionnaires used in more than one study are summarized in
Tables, Supplemental Digital Content 4, http://links.lww.
com/MSS/B259, and Supplemental Digital Content 5, http:// as above.
Anxiety/mood. Questionnaires used for anxiety and mood
can be seen in the supplementary tables (see Tables, Supple-
mental Digital Content 4,,
HIIT vs CON and Supplemental Digital Content 5, http://, HIIT vs MCT, which shows QoL
questionnaires used within studies). The most commonly
reported questionnaire to determine anxiety and mood was the
Hospital Anxiety and Depression Scale. Again due to paucity
of studies reporting values, no meta-analysis was performed
across HIIT versus CON or HIIT versus MCT. Flemmen et al.
(40) showed a significant reduction in anxiety favoring CON
(PG0.05) and a significant reduction in depression after
HIIT (PG0.05), with no significant difference in reported
insomnia. For HIIT versus MCT, both studies showed im-
provements in the Hospital Anxiety and Depression Scale
anxiety and depression domains, however, with no signifi-
cant benefit between intervention arms (42,57).
Adherence. Because of the widespread lack of reporting
and insufficient information included within published
papers, we deemed it inappropriate to analyze adherence
from the number of dropouts to each intervention, as very
few studies reported the direct reason for participants
dropping out in HIIT or MCT groups. Disparity in duration
of exercise (wk) led to varying numbers of scheduled ses-
sions per study. Overall, adherence to scheduled sessions
FIGURE 4—Forest plot showing meta-analysis of AT data for HIIT vs MCT (WMD mLIkg
). Diamonds to the right of the plot show benefit with HIIT.
SHORT-TERM HIIT IN COMORBIDITY Medicine & Science in Sports & Exercise
was high in both groups (see Table, Supplemental Digital
Content 6,, which shows
reported adherence to HIIT vs MCT protocols).
In this review of the current literature exploring the ef-
fectiveness of short duration HIIT in disease cohorts, we
found that HIIT elicits clinically important improvements
(91.5 mLIkg
within 8 wk or less when
compared with nonintervention control subjects.
young and older individuals (960 yr), where HIIT has been
shown to improve aspects of fitness. In healthy young in-
dividuals completing sprint interval training (4–6 intervals,
30-s all-out sprints), similar adaptations in human skeletal
muscle oxidative capacity and exercise performance to
those undertaking MCT (90–120 min continuous cycling at
65% V
) were seen in as little as 2 wk, despite a vastly
reduced time commitment and training volume (approxi-
mately 90% lower vs MCT) (68). Similarly, in healthy
older individuals, HIIT has been shown to increase V
(+8%) and reduce SBP (j9%) in just 6 wk (69). Moreover,
in a separate study of healthy older individuals, HIIT has
also recently been shown to elicit clinically significant
improvements in CRF within just 31 d (70), a time frame
that is compliant with the aforementioned UK National Can-
cer Action Team policy on time from decision to treat to sur-
gery. In addition to the reduced time frame and training
volume required by HIIT to elicit improvements in CRF, HIIT
may also have the added advantage of rapid adaptation at the
level of skeletal muscle, resulting in fewer negative training
symptoms (e.g., delayed onset muscle soreness [22]), which is
postulated to lead to increased adherence.
HIIT is at least as effective as MCT over short periodsacross
all groups. Subgroup analysis showed additional benefit in
cardiovascular patients versus other patient groups following
HIIT. To exemplify, cardiovascular patients showed addi-
tional increases in V
and AT after HIIT when compared
with MCT. It is likely that the rapid benefit shown in this
review is a result of peripheral adaptations such as mitochondrial
oxidative enzyme upregulation and increased buffering capacity
(68) as it is only in longer-term training programs (Q12 wk) that
improvements in cardiac structure and systolic function have
been shown (71). In response to HIIT, the contribution of car-
diac change may be underestimated because of the research
focus primarily being on mitochondrial upregulation, with
potential cardiac changes being understudied.
A small number patients with cancer were included in this
review, with varying outcomes. Lung, colon, and breast can-
cer groups all showed improvement in CRF with HIIT when
compared with no exercise. There was no added benefit of
HIIT over MCT. Blunted adaptation in these cancer groups
(shown as a lack of CRF improvement in response to HIIT
compared with the overall effect of HIIT vs CON) may be
explained by blunted mitochondrial enzyme activity while
cancers remain in situ (72). In addition, colorectal cancer
patients presenting for resection have lower CRF than age-
matched controls while the cancer is still in situ.However,
removal the cancer facilitates a return toward normal CRF
(73). Taken together, these studies may lead to a suggestion
that tumour presence hinders adaptive capacity to exercise
training, at least in this cancer type. Adjuvant chemotherapy
has negative effects on CRF preoperatively in colorectal
cancer patients (74) and have resulted in higher rates of heart
failure and cardiomyopathy after breast cancer chemotherapy
(75), as such these confounding drug regimens must be con-
sidered when interpreting trainability within these groups.
The beneficial psychological effects of exercise per se are
well known, but it is unclear whether HIIT is superior to MCT
in improving QoL from this review. This lack of clarity is due
to the heterogeneity of tools used, small numbers of studies
reporting QoL outcomes, and lack of suitable comparisons for
many of the questionnaires.
Beyond mechanistic propositions based on small-scale
nonrandomized control trials in distinct disease groups,
reasons why certain pathological subgroups might not show
CRF improvements with HIIT are far from clear. One pos-
sible explanation for certain subgroups is that exercise in-
tervention studies mainly report mean improvements in CRF
parameters as milliliters per kilogram per minute, rendering
obese patients at a relative disadvantage for demonstrating
improvement over short periods; as in the authors_experience,
individuals normally remain weight stable during short-term
HIIT protocols (often due to increased lean muscle mass and
fat mass reductions). A recent meta-analysis in obesity con-
cluded that HIIT was superior to traditional exercise to im-
prove CRF and reduce body fat percentage. Notably, the
median duration of training protocol for this meta-analysis
was 12 wk, with a wide range of 2–52 wk (76), which is does
not comply with clinical time frames for cancer surgery. By
contrast, but in agreement with this review, another recently
published meta-analysis found no clinical benefit of HIIT
versus MCT in reduction of total body fat or fat mass over
shorter training duration (G12 wk) (77).
To achieve benefit from HIIT, it is thought that a minimal dose
of exercise expenditure or training load is required to significantly
disturb intracellular homeostasis and stimulate mitochondrial
biogenesis (14). This may explain why the respiratory patients
seem to gain less benefit versus other pathological groups as
respiratory limitation may result in low maximal exercise scores
and therefore lower training loads, given that most protocols
prescribe the training load as a percentage of V
or max-
imal wattage achieved at cardiopulmonary exercise testing.
HIIT can represent a time efficient training method by
which to improve CRF, potentially removing the commonly
cited ‘‘lack of time’’ as a barrier to exercise (10). Time ef-
ficiency can be due to two facets, reduced work duration
within a session and/or individual session time. For exam-
ple, one of the most commonly used HIIT protocols within
studies in this review used 10 intervals of 1 min with 1-min
rest periods in between (32,49,52,58,59,62,66,78) totaling a
http://www.acsm-msse.org1746 Official Journal of the American College of Sports Medicine
session duration of ~20 min. However, another frequently
used HIIT protocol used four intervals of 4-min high-intensity
work with 3-min rest periods in between each bout, which led to
sessions typically lasting 930 min (12,31,32,36,40,44,55,79),
including a work duration of 16 min (vs 10 min in the afore-
mentioned example). Herein we show that, excluding warm-up
and end-of-session recovery periods, median work duration
during a HIIT session was half of that for MCT protocols
(16 vs 30 min). In addition, several studies in this review
(34,41,42,46,48,49,51,53,54,58–63) used low volume HIIT
protocols, involving 10 min (or less) total work duration (80).
Indeed, CRF improvements have been shown in as little as
10% of the training volume with HIIT when compared with
MCT (81). Taken in combination, reductions in regime du-
ration, total volume of training, and weekly time commitment
represent important drivers for enhancing adherence and re-
ducing costs associated with patient training. However, fur-
ther work is required to elucidate the optimal work-to-rest
ratios within HIIT protocols, which may further reduce the
total time commitment for the individual. It is also worth
noting that although the majority (990%) of studies within
this review used a static cycle ergometer for HIIT, other training
modalities (e.g., running) maybe viable. However, further work
is needed to assess the efficacy and tolerability when compared
with cycle ergometry within certain patient groups.
QoL and mood outcomes analyzed in this review were pre-
to posttraining program questionnaires, mostly global QoL
scores or disease specific questionnaires. These outcomes are
not specific enough to draw conclusions as to whether in-
dividuals preferred HIIT or MCT. However, as there were no
significant differences in the number of noncompliers, adherence
to scheduled sessions (see Table, Supplemental Digital Content
6,, which shows reported ad-
herence to HIIT vs MCT protocols) or reported serious adverse
events lead us to believe that neither HIIT nor MCT are inferior
for enjoyment, acceptability, or safety when compared.
Limitations. The studies in this review have a high risk
of bias, some of which is unavoidable because of the nature
of exercise intervention studies and the inability to blind
participants (see Figure, Supplemental Digital Content 3,, which shows risk of bias
summary chart). There is also a risk of contamination between
HIIT and nonintervention controls. In addition, heterogeneity
among HIIT protocols, training duration, chronological age,
and pathology leads to uncertainty about the true effectiveness
of interventions (82) [see Tables, Supplemental Digital Con-
tent 1,, Paper Characteristics
(HIIT vs CON); Supplemental Digital Content 2, http://links., Paper Characteristics (HIIT vs MCT);
Supplemental Digital Content 7,
B262, Training regimes (HIIT vs CON); and Supplemental
Digital Content 8,, Training
regimes (HIIT vs MCT)].
We have shown that HIIT leads to clinically significant
improvements in CRF within 8 wk in patients with disease,
when compared with no intervention. HIIT also resulted in
statistically significant improvements in CRF compared with
MCT, with clinically significant benefit seen in cardiovas-
cular patients. Because of the reduced exercise volume and
improved efficacy (vs MCT) in certain clinical groups, HIIT
can be promoted as a viable clinical exercise intervention to
rapidly improve CRF.
This work was supported by the Medical Research Council (grant
no. MR/K00414X/1), the Arthritis Research UK (grant no. 19891)
awarded to the MRC-ARUK Centre for Musculoskeletal Ageing Re-
search, and the Dunhill Medical Trust (grant no. R468/0216).
The authors declare no conflicts of interest. The results of the
present study do not constitute endorsement by the American Col-
lege of Sports Medicine. The results of the study are presented
clearly, honestly, and without fabrication, falsification, or inappro-
priate data manipulation.
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SHORT-TERM HIIT IN COMORBIDITY Medicine & Science in Sports & Exercise

Supplementary resource (1)

... A 2018 meta-analysis by Blackwell and colleagues, reported mean difference (MD) of 3.38 (95% CI 2.7-4.05) ml/kg/min between HIIT and control groups, in less than eight weeks in a population with diverse disease [21]. Metabolic adaptations on oxidative capacity and peripheral insulin sensitivity, along with improvements in cardiac and respiratory function, are achieved by the higher intensities reached in each exercise session [19,22]. ...
... VO 2peak defines a metric that is associated with risk in surgery, in particular thoracic surgery and consequently represents a modifiable factor for HIIT. Two recent meta-analysis reported HIIT to be effective across the cancer care continuum and in other clinical populations (endocrine, cardiovascular, respiratory and psychiatry) [20,21]. After results pooling and analysis of the five papers, there was no significant MD between HIIT versus usual care or moderate intensity exercise. ...
... The longest intervention (mean duration 54 days) had one of the lowest intensity interventions and reported a significant increase in preoperative fitness [28]. Blackwell and colleagues compared the effect HIIT versus usual care on VO 2peak in less than eight weeks in a recent meta-analysis [21]. Nine of the 13 studies included prescribed peak intensities of >90% of WRp or VO 2peak and all reported a significant improvement VO 2peak [21]. ...
Exercise prehabilitation prior to major surgery targets a reduction in postoperative complications through improved conditioning and respiratory function. However its effectiveness in cancer surgery is unclear. The objective of this review was to determine if preoperative high-intensity interval training (HIIT) improves preoperative fitness in patients scheduled for oncologic resection, and whether postoperative complications are impacted. Methods CINAHL, AMED, PEDro, EMBASE, The Cochrane Library and PubMed/MEDLINE were searched until April 2021 using predefined search strategy and accompanied by manual forward and backwards citation review. Screening of titles, abstracts, full-texts, data extraction, risk of bias assessment and methodologic quality was performed independently by two reviewers. Mean difference (MD) with 95% confidence intervals (CI) was compared and heterogeneity assessed using Chi Squared Test and I² statistic. Six randomised controlled trials (RCTs) were included in the systematic review. Interventions prescribed bouts of high-intensity exercise [80–115% peak work rate (WRp) interspaced with low-intensity (rest-50% WRp) exercise. The meta-analysis included five RCTs reporting peak oxygen consumption (VO2peak). Preoperative HIIT did not result in significantly higher VO2peak in comparison to usual care or moderate intensity exercise (MD 0.83, 95%CI-0.51–2.17) kg/ml/min, p = 0.12). Studies were insufficiently powered with respect to postoperative complications, but there is no evidence of significant impact. No adverse events occurred and high adherence rates were reported. Results of this systematic review and meta-analysis demonstrate there is insufficient evidence to support HIIT as a method of improving preoperative fitness prior to oncologic resection. Further work is needed to determine if specific HIIT parameters can be adapted to improve efficacy over short time-frames.
... The study screening strategy is presented in the form of a flow chart (Appendix 2). Seven systematic reviews met the inclusion criteria, six of the included studies were systematic reviews and meta-analysis [45][46][47][48][49][50] , while the remaining study was a systematic reviews without quantitative synthesis 51 . The characteristics of the included studies (study design, origina l studies included, demographic characteristics, interventions, outcomes and results) are presented in Tables 1 and 2. Some of the original studies were included in several reviews, with a duplication rate of 44%, but none of the included reviews presented exactly the same studies (Appendix 3). ...
... Regarding risk of bias, two systematic reviews had a low risk of bias 47,50 , while the remaining five had a high risk of bias. The domain "synthesis of findings" presented the highest risk of bias (Table 4 and Figure 1). ...
... Five of the studies found a significant increase in VO2 max when implementing HIIT versus OT, both added to the first-choice cancer treatment. Three of these studies used prehabilitation and rehabilitation HIIT [48][49][50] , one only prehabilitation 45 Table 5). ...
Full-text available
Objective: To assess the available evidence on the effectiveness of high-intensity interval training (HIIT) in addition to first-choice cancer treatment on cardiorespiratory fitness (CRF), quality of life (QoL), adherence, and adverse effects of HIIT in patients with cancer or cancer survivors. Methods: An umbrella review and meta-meta-analysis (MMA) was performed. A systematic search was conducted in MEDLINE, EMBASE, Cochrane Database, CINAHL, Scopus, SPORTDiscus and Web of Science until August 2021. Article selection, quality assessment, and risk of bias assessment were performed by two independent reviewers. The MMA were performed with a random-effects model and the summary statistics were presented in the form of forest plot with a weighted compilation of all standardised mean differences (SMD) and corresponding 95% confidence interval (CI). Results: Seven systematic reviews were included. Regarding CRF, the addition of HIIT to cancer treatment showed statistically significant differences with a small clinical effect, compared to adding other treatments (SMD=0.45; 95% CI 0.24 to 0.65). There was no significant difference when compared to adding moderate-intensity continuous training (MICT) (SMD=0.23; 95% CI -0.04 to 0.50). QoL showed positive results although with some controversy. Adherence to HIIT intervention was high, ranging from 54 to 100%. Regarding adverse effects, most of the systematic reviews reported none, and in the cases in which they occurred, they were mild. Conclusion: In conjunction with first-choice cancer treatment, HIIT has been shown to be an effective intervention in terms of CRF and QoL, as well as having optimal adherence rate. In addition, the implementation of HIIT in patients with cancer or cancer survivors is safe as it showed no or few adverse effects.
... A recent systematic review [18] summarized data concerning efficacy of VER in healthy participants and concluded that this is a robust approach to confirm the value acquired from incremental exercise. However, having a more accurate estimate of 'true' VO 2 max in this active population may not be that important as their cardiorespiratory fitness is superior, leading to enhanced health status versus less fit populations. ...
... In addition, studies using participants who have or are at risk for chronic disease were included, which encompassed the following populations: inactive adults or children; adults with obesity; older adults >50 years; and adults or children with underlying disease including cancer, diabetes, cardiovascular disease, etc. These criteria were chosen as a recent review paper extensively summarized the efficacy of verification testing in healthy adults [18]. Studies were excluded if submaximal protocols were used to assess VO 2 max, as well as those not acquiring gas exchange data. ...
Full-text available
Maximal oxygen uptake (VO2max) is strongly associated with endurance performance as well as health risk. Despite the fact that VO2max has been measured in exercise physiology for over a century, robust procedures to ensure that VO2max is attained at the end of graded exercise testing (GXT) do not exist. This shortcoming led to development of an additional bout referred to as a verification test (VER) completed after incremental exercise or on the following day. Workloads used during VER can be either submaximal or supramaximal depending on the population tested. Identifying a true VO2max value in unhealthy individuals at risk for or having chronic disease seems to be more paramount than in healthy and active persons, who face much lower risk of premature morbidity and mortality. This review summarized existing findings from 19 studies including 783 individuals regarding efficacy of VER in unhealthy individuals to determine its efficacy and feasibility in eliciting a ‘true’ VO2max in this sample. Results demonstrated that VER is a safe and suitable approach to confirm attainment of VO2max in unhealthy adults and children, as in most studies VER-derived VO2max is similar of that obtained in GXT. However, many individuals reveal higher VO2max in response to VER and protocols used across studies vary, which merits additional work identifying if an optimal VER protocol exists to elicit ‘true’ VO2max in this particular population.
... Regarding the second objective, thresholds for values of skeletal muscle mass concerning body height (SMI) and body fat (MFR) reflected the chance of positive changes in the cardiovascular system (particularly systolic blood pressure). Interventions based on aerobic and anaerobic exercise are widely used in programs related to human health [51][52][53][54]. Particularly, high-intensity interval training is an effective method for improving health parameters considering body composition and hemodynamics parameters of physical fitness (martin smith). ...
Full-text available
This study aimed to investigate the prognostic potential of body composition indices in predicting the improvement in resting blood pressure after 10 weeks of high-intensity interval training (HIIT) implemented in physical education lessons. The participants were 141 adolescents aged 16 years. Independent variables were body mass index (BMI), fat mass index (FMI), muscle mass index (SMI), and mass to fat ratio (MFR); dependent variables were systolic and diastolic blood pressure (SBP, DBP) and its indices: pulse pressure (PP), mid-blood pressure (MBP), and mean arterial pressure (MAP). The receiver operating curve (ROC) method was employed. SMI and MFR are body composition indices with prognostic potential to predict positive changes in SBP in males (SMI: AUC = 0.82; p < 0.001, MFR = 0.70; p = 0.039) and MFR in females (AUC = 0.72; p = 0.035). The respective cut-off point values used to classify participants as a beneficiary of HIIT intervention concerning SBP were SMI = 7.84 and MFR = 2.43 in males, and for SMI = 10.12 and MFR = 1.94 in females. Body composition indices based on skeletal muscle (SMI, MFR) were more likely to predict positive changes in SBP after HIIT intervention in adolescents. PP, MBP, and MAP did not reflect the detecting power of SMI and MFR. However, these thresholds’ utility is limited to adolescents of 16 years of age.
... Due to inconsistent reporting of mean changes and change standard deviations (SDs), we calculated these using formulae from the Cochrane Handbook. We assumed a correlation coefficient of 0.7 between baseline and final values based on analysis of our previous, similar data [27]. When data were reported using l/min, we transformed data to ml/kg/min using average weight values from the study. ...
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Background Declines in cardiorespiratory fitness (CRF) and muscle mass are both associated with advancing age and each of these declines is associated with worse health outcomes. Resistance exercise training (RET) has previously been shown to improve muscle mass and function in the older population. If RET is also able to improve CRF, as it has been shown to do in younger populations, it has the potential to improve multiple health outcomes in the expanding older population. Methods This systematic review aimed to identify the role of RET for improving CRF in healthy older adults. A search across CINAHL, MEDLINE, EMBASE and EMCARE databases was conducted with meta-analysis performed on eligible papers to identify improvements in established CRF parameters (VO2 peak, aerobic threshold (AT), 6-minute walking distance test (6MWT) following RET intervention. Main eligibility criteria included older adults (aged over 60), healthy cohorts (disease-specific cohorts were excluded) and RET intervention. Results Thirty-seven eligible studies were identified. Meta-analysis revealed a significant improvement in VO2 peak (MD 1.89 ml/kg/min; 95% confidence interval (CI) 1.21–2.57 ml/kg/min), AT (MD 1.27 ml/kg/min; 95% CI 0.44–2.09 ml/kg/min) and 6MWT (MD 30.89; 95% CI 26.7–35.08) in RET interventions less than 24 weeks. There was no difference in VO2 peak or 6MWT in interventions longer than 24 weeks. Discussion This systematic review adds to a growing body of evidence supporting the implementation of RET in the older population for improving whole-body health, particularly in time-limited timeframes.
... HIIT was successfully tested in a variety of patient populations affected by chronic diseases, e.g., obesity, metabolic and cardiovascular disease [56,57]. In cancer, investigations of prehabilitative HIIT are limited; to date, only four controlled trials explored HIIT in presurgical patients affected by rectal [58], lung [35], bladder [59], and colorectal cancer with liver metastases [60]. ...
Despite several recent advances, lung cancer surgery is still associated with potentially severe postoperative complications. It has been suggested that preoperative exercise training could render patients with borderline functional parameters eligible for surgery, improve perioperative outcomes and that these benefits might reduce healthcare costs. Nevertheless, given the substantial heterogeneity of the available studies, no specific guidelines for preoperative exercise training have been released so far. This narrative review aims to provide an overview of the potential benefits of exercise training in the preoperative period as a central intervention for lung cancer patients. In detail, the effects of exercise (with different regimens) were evaluated in terms of physical functions, patients’ eligibility for curative surgery, postoperative complications and length of stay, with an exploratory focus on healthcare costs and long-term outcomes. Furthermore, a feasible approach for every-day clinical practice is proposed in order to increase the expected benefit deriving from a more extensive and methodical application of prehabilitation exercise, ideally in the context of a comprehensive approach to lung cancer patients, including nutritional and psychological support.
... Similar to our results, Cassidy et al. (13) evaluated diabetics after 12 wks training HIIT, and they observed a significant decrease (23). About types of HIIT, Other studies have investigated the effects of the short HIIT on the blood glucose after 8 wks and found a significant decrease (11). The same results were found by Ito (21) after 2 wks of long HIIT in diabetic subjects. ...
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The purpose of this study was to evaluate the chronic autonomic cardiac modulation and metabolic effects of 12 wks of long or short HIIT in adults with T2DM. Fifteen T2DM patients (52 ± 13,7 yrs) were submitted to 12 wks of intervention (24 sessions of 30 min). The sample was divided in 3 groups: (a) Short HIIT-30 sec in 90%VO2peak, followed by 30 sec recovery; (b) Long HIIT-120 sec in 85%VO2peak, followed by 120 sec recovery; and (c) Control Group-did not perform any exercise. We measured blood parameters, cardiopulmonary level, body composition, and heart rate variability (HRV) before and after 12 wks. The results demonstrated that long HIIT improved significantly the cardiac modulation and the VO2peak. Both exercise protocols improved significantly the glycemic control. This study indicates that long-HIIT is an interesting strategy to improve metabolic and cardiopulmonary functions, which can help to prevent the development of diabetic heart diseases in T2DM patients.
... Our sample size per group is similar to previous research comparing efficacy of HIIT in young adults completing different exercise regimens [5,30,34]. In addition, data show that an increase in VO 2 max as small as 1.5 ml/kg/min is clinically meaningful [35]. ...
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Data obtained in primarily Caucasian (C) and African American adults show that ethnicity does not mediate responsiveness to exercise training. It is unknown if Hispanics (H), who face elevated health risks and are less active than C, exhibit a similar response to exercise training. This study compared cardiorespiratory and hemodynamic responses to high intensity interval training (HIIT) between C and H women. Twelve C and ten H women ages 19–35 yr who were non-obese and inactive completed nine sessions of HIIT over a 3 wk period. Maximal oxygen uptake (VO 2 max) was assessed twice at baseline during which thoracic impedance was used to evaluate heart rate (HR), stroke volume (SV) and cardiac output (CO). Habitual physical activity was assessed using accelerometry. Results showed a significant main effect of training for VO 2 max in C and H (F = 13.97, p = 0.001) and no group by training interaction (p = 0.65). There was a main effect of training for CO and SV in C and H (F = 7.57, p = 0.01; F = 7.16, p = 0.02), yet post hoc analyses revealed significant increases were only exhibited in C. There was a tendency for a group by training interaction for a-VO 2 diff (F = 1.32, p = 0.054), and a large effect size was seen in H (d = 1.02). Overall, data show no effect of ethnicity on changes in VO 2 max with low-volume HIIT, yet C and H may achieve this outcome differently. Longer studies in similar populations are needed to verify this result.
Introduction: High-intensity interval training (HIIT) and sprint interval training (SIT) significantly increase maximal oxygen uptake (V̇O2max) which enhances endurance performance and health status. Whether this response is due to increases in central cardiovascular function (cardiac output and blood volume) or peripheral factors is unknown. Purpose: To conduct a systematic review and meta-analysis to assess the effects of HIIT and SIT (referred to as intense interval training) on changes in central cardiovascular function. Methods: We performed a systematic search of eight databases for studies denoting increases in V̇O2max in which cardiac output (CO), stroke volume (SV), blood volume, plasma volume, end-diastolic/systolic volume, or hematocrit were measured. Results: Forty-five studies were included in this analysis, comprising 946 men and women of various health status (age and V̇O2max = 20 - 76 yr and 13 - 61 mL·kg-1·min-1) who performed 6 - 96 sessions of interval training. Results showed an increase in V̇O2max with intense interval training that was classified as a large effect (d = 0.83). Stroke volume (d = 0.69) and CO (d = 0.49) had moderate effect sizes in response to intense interval training. Of 27 studies in which CO was measured, 77 % exhibited significant increases in resting CO or that obtained during exercise. Similarly, 93 % of studies revealed significant increases in SV in response to intense interval training. Effect sizes for these outcomes were larger for clinical versus healthy populations. Plasma volume, blood volume, and hematocrit had small effect sizes after training (d = 0.06 - 0.14). Conclusions: Increases in V̇O2max demonstrated with intense interval training are attendant with increases in central O2 delivery with little contribution from changes in hematocrit, blood volume, or plasma volume.
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Introduction Non-muscle invasive bladder cancer (NMIBC) accounts for about 75% of newly diagnosed bladder cancers. The treatment for NMIBC involves surgical removal of the tumour followed by 6 weekly instillations of immunotherapy or chemotherapy directly into the bladder (ie, intravesical therapy). NMIBC has a high rate of recurrence (31%–78%) and progression (15%). Moreover, bladder cancer and its treatment may affect patient functioning and quality of life. Exercise is a safe and effective intervention for many patient with cancer groups, however, no studies have examined exercise during intravesical therapy for NMIBC. The primary objective of the Bladder cancer and exeRcise trAining during intraVesical thErapy (BRAVE) trial is to examine the safety and feasibility of an exercise intervention in patients with bladder cancer undergoing intravesical therapy. The secondary objectives are to investigate the preliminary efficacy of exercise on health-related fitness and patient-reported outcomes; examine the social cognitive predictors of exercise adherence; and explore the potential effects of exercise on tumour recurrence and progression. Methods and analysis BRAVE is a phase II randomised controlled trial that aims to include 66 patients with NMIBC scheduled to receive intravesical therapy. Participants will be randomly assigned to the exercise intervention or usual care. The intervention consists of three supervised, high-intensity interval training sessions per week for 12 weeks. Feasibility will be evaluated by eligibility, recruitment, adherence and attrition rates. Preliminary efficacy will focus on changes in cardiorespiratory fitness and patient-reported outcomes from baseline (prior to intravesical therapy) to pre-cystoscopy (3 months). Cancer outcomes will be tracked at 3 months, and 1-year follow-up by cystoscopy. Analysis of covariance will compare between-group differences at post-intervention (pre-cystoscopy) for all health-related fitness and patient-reported outcomes. Ethics and dissemination The study was approved by the Health Research Ethics Board of Alberta-Cancer Committee (#20–0184). Dissemination will include publication and presentations at scientific conferences and public channels. Trial registration number NCT04593862 ; Pre-results.
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Introduction High Intensity training (HIT) is a time‐effective alternative to traditional exercise programs in adults with obesity, but the superiority in terms of improving cardiopulmonary fitness and weight loss has not been demonstrated. Objective to determine the effectiveness of HIT on cardiopulmonary fitness and body composition in adults with obesity compared to traditional (high volume continuous) exercise. Methods A systematic search of the main health science databases was conducted for randomized controlled trials comparing HIT with traditional forms of exercise in people with obesity. Eighteen studies were included in the meta‐analysis. The (unstandardized) mean difference of each outcome parameters was calculated and pooled with the random effects model. Results HIT resulted in greater improvement of cardiopulmonary fitness (VO2max) (MD 1.83, 95% CI 0.70, 2.96, p<0.005; I²=31%) and a greater reduction of %body fat (MD ‐1.69, 95% CI ‐3.10, ‐0.27, p=0.02, I²=30%) compared to traditional exercise. Overall effect for BMI was not different between HIT and traditional exercise. Conclusion Training at high intensity is superior to improve cardiopulmonary fitness and to reduce %body fat in adults with obesity compared to traditional exercise. Future studies are needed to design specific HIT programs for the obese with regard to optimal effect and long‐term adherence.
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Increasing evidence suggests that high-intensity training (HIT) is a time-efficient exercise strategy to improve fitness. HIT has never been explored in neuromuscular diseases, likely because it may seem counterintuitive. A single session of high-intensity exercise has been studied without signs of muscle damage in facioscapulohumeral muscular dystrophy type 1 (FSHD1). We aimed to determine whether HIT is safe and effective in FSHD1 in a randomized, controlled parallel study. Untrained adults with genetically verified FSHD1 (n = 13) able to perform cycle-ergometer exercise were randomized to 8 weeks of supervised HIT (n = 6) (3 × 10-min cycle-ergometer-HIT/week) or 8 weeks of usual care (n = 7). Following this, all participants performed 8 weeks of unsupervised HIT (3 × 10-min cycle-ergometer-HIT/week). Primary outcome was fitness, maximal oxygen uptake/min/kg body weight. Furthermore, workload, 6-min walk distance, 5-time sit-to-stand time, muscle strength, and daily activity levels were measured. Pain, fatigue, and plasma-CK were monitored. Twelve patients completed the randomized part of the study. Plasma-CK levels and pain scores were unaffected by HIT. Supervised HIT improved fitness (3.3 ml O2/min/kg, CI 1.2-5.5, P < 0.01, n = 6, NNT = 1.4). Unsupervised HIT also improved fitness (2.0 ml O2/min/kg, CI 0.1-3.9, P = 0.04, n = 4). There was no training effect on other outcomes. Patients preferred HIT over strength and moderate-intensity aerobic training. It may seem counterintuitive to perform HIT in muscular dystrophies, but this RCT shows that regular HIT is safe, efficacious, and well liked by moderately affected patients with FSHD1, which suggests that HIT is a feasible method for rehabilitating patients with FSHD1.
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Introduction: Prehabilitation programs aim to optimise patients in order to enhance post-operative recovery. This study aims to review the composition of prehabilitation programs for patients undergoing major abdominal cancer surgery and define the outcome measures that are used to evaluate this intervention. Methods: A systematic literature review of all comparative studies on prehabilitation versus standard care in patients undergoing abdominal cancer surgery was performed in accordance with PRISMA guidelines. Literature search was performed using Medline, OVID, EMBASE, Google Scholar, and Cochrane databases. Outcomes of interest included prehabilitation program composition (exercise, nutritional, and psychological interventions), duration, mode of delivery, and outcome measures used to determine impact of prehabilitation versus standard care. Results: 9 studies (7 randomised controlled and 2 prospective non-randomised trials) comprising of 549 patients (281 prehabilitation versus 268 standard care) were included in this review. 5 studies reported patients undergoing surgery for colorectal cancer, 2 for bladder tumours, 1 for liver resections, and 1 involving unspecified abdominal oncological operations. The 6 minute walk test (6MWT) was used in 4 studies to measure functional capacity with a threshold of >20m improvement at 4-8 weeks post-operatively deemed significant (distance range from 278-560m). Changes in anaerobic threshold and VO2(max) with prehabilitation were evaluated in 5 studies (ml/kg/min). Health-related quality of life was evaluated using SF-36 system, anxiety assessed using hospital anxiety and depression score (HADS). Post-operative complications were classified according to the Clavien-Dindo classification with no significant difference between prehabilitation and standard care groups. Conclusion: Prehabilitation programs in patients undergoing abdominal cancer surgery remain heterogeneous in their composition, mode of administration, outcome measures of functional capacity that are used to evaluate their impact. All these aspects require standardisation prior to the evaluation of prehabilitation on a larger scale.
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Background: Impairment in aerobic fitness is a potential modifiable risk factor for postoperative complications. In this randomized controlled trial, we hypothesized that a high-intensity interval training (HIIT) program enhances cardiorespiratory fitness before lung cancer surgery and therefore reduces the risk of postoperative complications. Methods: Patients with operable lung cancer were randomly assigned to usual care (UC, N=77) or preoperative rehabilitation based on HIIT (Rehab, N=74). Maximal cardiopulmonary exercise testing and the six-minute walk test were performed twice before surgery. The primary outcome measure was a composite of death and in-hospital postoperative complications. Results: Groups were well balanced in terms of patient characteristics. During the preoperative waiting period (median 25 days), the peak oxygen consumption (peakVO2) and the six-minute walking distance increased (respectively, median +15 % [IQ 25-75%, +9 to +22%] P=0.003 and +15% [IQ25-75, +8 to +28%], P<0.001) in the Rehab group whereas VO2peak declined in the UC group (median -8% [IQ25-75, -16 to 0%], P=0.005). The primary endpoint did not differ significantly between the two groups: 27 of the 74 patients (35.5%) in the Rehab group and 39 of 77 patients (50.6%) in the UC group developed at least one postoperative complication (P=0.080). Noteworthy, the incidence of pulmonary complications was lower in the Rehab compared with the UC group (23% vs 44%, P=0.018), owing to a significant reduction in atelectasis (12.2% vs 36.4%, P<0.001) and this was accompanied by a shorter length of stay in the postanesthesia care unit (median -7 hours, IQ25-75% -4 to -10). Conclusions: In this RCT, preoperative HIIT resulted in significant improvement in aerobic performances but failed to reduce early complications after lung cancer resection.
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The purpose of the study was to examine the effects of sprint interval training (SIT) and moderate-intensity continuous cycle training (MICT), with equal estimated energy expenditure during training on body composition and aerobic capacity. Body composition measured via dual-energy X-ray absorptiometry and aerobic capacity were assessed following 6 weeks of training in previously inactive overweight/obese young women (n = 52; age, 20.4 ± 1.5 years; body mass index, 30.3 ± 4.5 kg·m(-2), 67.3% white). Training was performed in a group-exercise format that mimicked cycling classes offered by commercial fitness facilities, and included 3 weekly sessions of either 30-s "all-out" sprints followed by 4 min of active recovery (SIT), or continuous cycling at 60%-70% heart rate reserve to expend a similar amount of energy. Participants were randomized to SIT or MICT, attended a similar number of sessions (15.0 ± 1.5 sessions vs. 15.8 ± 1.9 sessions, P = 0.097) and expended a similar amount of energy (541.8 ± 104.6 kJ·session(-1) vs. 553.5 ± 138.1 kJ·session(-1), P = 0.250). Without significant changes in body mass (P > 0.05), greater relative reductions occurred in SIT than in MICT in total fat mass (3.6% ± 5.6% vs. 0.6% ± 3.9%, P = 0.007), and android fat mass (6.6% ± 6.9% vs. 0.7% ± 6.5%, P = 0.002). Aerobic capacity (mL·kg(-1)·min(-1)) increased significantly following both interventions (P < 0.05), but the relative increase was 2-fold greater in SIT than in MICT (14.09% ± 10.31% vs. 7.06% ± 7.81%, P < 0.001). In conclusion, sprint-interval cycling reduces adiposity and increases aerobic capacity more than continuous moderate-intensity cycling of equal estimated energy expenditure in overweight/obese young women.
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Objective: The aim of this study was to compare the effects of 5-week high-intensity interval training (HIIT) and moderate-to-vigorous intensity continuous training (MVCT) on cardiometabolic health outcomes and enjoyment of exercise in obese young women. Methods: A randomized controlled experiment was conducted that involved thirty-one obese females (age range of 18-30) randomly assigned to either HIIT or MVCT five-week training programs. Participants in HIIT condition performed 20 min of repeated 8 s cycling interspersed with 12 s rest intervals, and those in MVCT condition cycled continuously for 40 min at 60-80% of peak oxygen consumption ([Formula: see text]O2peak), both for four days in a week. Outcomes such as [Formula: see text]O2peak, body composition estimated by bioimpedance analysis, blood lipids, and serum sexual hormones were measured at pre-and post-training. The scores of Physical Activity Enjoyment Scale (PAES) were collected during the intervention. Results: After training, [Formula: see text]O2peak increased significantly for both training programs (9.1% in HIIT and 10.3% in MVCT) (p = 0.010, η2 = 0.41). Although MVCT group had a significant reduction in total body weight (TBW, -1.8%, p = 0.034), fat mass (FM, - 4.7%, p = 0.002) and percentage body fat (PBF, -2.9%, p = 0.016), there were no significant between-group differences in the change of the pre- and post-measures of these variables. The HIIT group had a higher score on PAES than the MVCT group during the intervention. For both conditions, exercise training led to a decline in resting testosterone and estradiol levels, but had no significant effect on blood lipids. Conclusion: Both HIIT and MVCT are effective in improving cardiorespiratory fitness and in reducing sexual hormones in obese young women; however, HIIT is a more enjoyable and time-efficient strategy. The mild-HIIT protocol seems to be useful for at least maintaining the body weight among sedentary individuals.
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Exercise training provides physiological benefits for both improving athletic performance and for maintaining good health. Different exercise training modalities and strategies exist. Two common exercise strategies are high-intensity interval training (HIIT) and moderate-intensity continuous exercise training (MCT). HIIT was first used early in the 20th century and popularized later that century for improving performance of Olympic athletes. The primary premise underlying HIIT is that, compared to energy expenditure-matched MCT, a greater amount of work is performed at a higher intensity during a single exercise session which is achieved by alternating high-intensity exercise intervals with low-intensity exercise or rest intervals. Emerging research suggests that this same training method can provide beneficial effects for patients with a chronic disease and should be included in the comprehensive medical management plan. Accordingly, a major consideration in developing an individual exercise prescription for a patient with a chronic disease is the selection of an appropriate exercise strategy. In order to maximize exercise training benefits, this strategy should be tailored to the individual's need The focus of this paper is to provide a brief summary of the current literature regarding the use of HIIT to enhance the functional capacity of individuals with cardiovascular, pulmonary, and diabetes diseases.
Interval training (including high-intensity interval training [HIIT] and sprint interval training [SIT]) is promoted in both scientific and lay media as being a superior and time-efficient method for fat loss compared with traditional moderate-intensity continuous training (MICT). We evaluated the efficacy of HIIT/SIT when directly compared with MICT for the modulation of body adiposity. Databases were searched to 31 August 2016 for studies with exercise training interventions with minimum 4-week duration. Meta-analyses were conducted for within-group and between-group comparisons for total body fat percentage (%) and fat mass (kg). To investigate heterogeneity, we conducted sensitivity and meta-regression analyses. Of the 6,074 studies netted, 31 were included. Within-group analyses demonstrated reductions in total body fat (%) (HIIT/SIT: -1.26 [95% CI: -1.80; -0.72] and MICT: -1.48 [95% CI: -1.89; -1.06]) and fat mass (kg) (HIIT/SIT: -1.38 [95% CI: -1.99; -0.77] and MICT: -0.91 [95% CI: -1.45; -0.37]). There were no differences between HIIT/SIT and MICT for any body fat outcome. Analyses comparing MICT with HIIT/SIT protocols of lower time commitment and/or energy expenditure tended to favour MICT for total body fat reduction (p = 0.09). HIIT/SIT appears to provide similar benefits to MICT for body fat reduction, although not necessarily in a more time-efficient manner. However, neither short-term HIIT/SIT nor MICT produced clinically meaningful reductions in body fat.
We hypothesized that high-intensity interval training (HIIT) would be more effective than moderate-intensity continuous training (MICT) at improving endothelial function and maximum oxygen uptake (VO2max) in obese adults. Eighteen participants (35.1 ± 8.1 y; BMI = 36.0 ± 5.0 kg/m2) were randomized to eight weeks (3 sessions/week) of either HIIT (10 x 1 min, 90-95% maximum heart rate (HRmax), 1 min active recovery) or MICT (30 min, 70-75% HRmax). Brachial artery flow-mediated dilation (FMD) increased after HIIT (5.13 ± 2.80% vs. 8.98 ± 2.86%, P = 0.02) but not after MICT (5.23 ± 2.82% vs. 3.05 ± 2.76%, P = 0.16). Resting artery diameter increased after MICT (3.68 ± 0.58 mm vs. 3.86 ± 0.58 mm, P = 0.02), but not after HIIT (4.04 ± 0.70 mm vs. 4.09 ± 0.70 mm; P = 0.63). There was a significant (P = 0.02) group x time interaction in low-flow mediated constriction (L-FMC) between MICT (0.63 ± 2.00% vs. -2.79 ± 3.20%; P = 0.03) and HIIT (-1.04 ± 4.09% vs. 1.74 ± 3.46%; P = 0.29). VO2max increased (P < 0.01) similarly after HIIT (2.19 ± 0.65 L/min vs. 2.64 ± 0.88 L/min) and MICT (2.24 ± 0.48 L/min vs. 2.55 ± 0.61 L/min). Biomarkers of cardiovascular risk and endothelial function were unchanged. HIIT and MICT produced different vascular adaptations in obese adults, with HIIT improving FMD and MICT increasing resting artery diameter and enhancing L-FMC. HIIT required 27.5% less total exercise time and approximately 25% less energy expenditure than MICT.
Background: Post-stroke guidelines recommend moderate-intensity continuous aerobic training (MCT) to improve aerobic capacity and mobility after stroke. High-intensity interval training (HIT) has been shown to be more effective than MCT among healthy adults and persons with heart disease. However, HIT and MCT have not been previously compared among persons with stroke. Objective: Assess the feasibility and justification for a definitive randomized controlled trial (RCT) comparing HIT and MCT in chronic stroke. Design: Pilot RCT. Setting: Cardiovascular stress laboratory and rehabilitation research laboratory. Patients: Ambulatory persons at least 6 months post-stroke. Intervention: Both groups trained 25 minutes, 3 times per week for 4 weeks. HIT involved 30 second bursts at maximum tolerated treadmill speed alternated with 30-60 second rest periods. MCT involved continuous treadmill walking at 45-50% heart rate reserve. Measurements: Measurements included recruitment and attendance statistics, qualitative HIT acceptability, adverse events and the following blinded outcome variables: peak oxygen uptake, ventilatory threshold, metabolic cost of gait, fractional utilization, fastest treadmill speed, 10m walk test and 6 minute walk test. Results: In 8 months, 26 participants consented. Eighteen were enrolled and randomized to HIT (n=13) or MCT (n=5). Eleven out of 13 HIT group participants attended all sessions. Participants reported that HIT was acceptable and no serious adverse events occurred. Standardized effect size estimates between groups were moderate to very large for most outcomes. Only 30% of treadmill speed gains in the HIT group translated into overground gait speed improvement. Limitations: Not designed to definitively test safety or efficacy. Conclusions: Although further protocol optimization is needed to improve overground translation of treadmill gains, a definitive RCT comparing HIT and MCT appears to be feasible and warranted.