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potentially translated into better exercise capacity in
daily life settings. We previously published the clini-
cal impact of this particular intervention on surgery
outcome (16). The pulmonary complications, mainly
atelectasis, were reduced by 45% in PH and the effect
was more pronounced in patients who demonstrated
a greater response to HIIT. This resulted in a mild
reduction in the length of stay in the post-anaesthesia
care unit (median –7 h, IQ25–75% –4 to –10 h) (16).
Our finding that just 8 training sessions over 3 weeks
resulted in a significant improvement in fitness is in
agreement with earlier work. HIIT was shown to result
rapidly in positive aerobic effects; just 6 sessions of
HIIT can produce these changes due to an increase in
the mitochondrial content, thereby enhancing oxygen
uptake (22). Several meta-analyses of controlled trials
also confirmed that HIIT increases VO 2peak and that the
effect is greater for candidates who are less fit (14,
23). In addition, HIIT improves fitness in patients with
severe heart disease (17).
At baseline the mean VO 2peak and mean 6MWT
distance were 18% and 42%, respectively, below the
predicted values in these patients (16). It has been
shown that cardio-respiratory fitness is an independent
factor in mortality and length of hospitalization (24).
In individuals undergoing non-cardiac surgical proce-
dures high levels of preoperative function, in particular
higher cardio-respiratory fitness, are associated with
better survival after surgery (24–26). Due to the design
of the current study it was not possible to include only
severely deconditioned patients. However, it is possible
that the more severely deconditioned patients could
benefit the most, as suggested by the observed changes
in resting heart rate.
Resting heart rate (measured in standardized condi-
tions) was lowered as a result of the exercise training
in our patients. A low resting heart rate is characteristic
of a higher fitness level and is a predictor of all-cause
mortality (27). It was demonstrated that HIIT improved
resting heart rate more than did other modes of training
in patients with coronary artery disease (28). Numerous
trials have shown a mean decrease in resting heart rate
of 3–10 bpm after HIIT training, conducted for 8 weeks,
12 weeks or 6 months, at 60–90% of W peak (29, 30). We
saw a mean reduction in resting heart rate of 6 bpm after
a median of 8 HIIT sessions at 100% of W peak . Since
there was no significant change in HR rest between the first
and the intermediate HIIT sessions, it can be assumed
that it takes approximately 2–3 weeks to notice the first
changes with this type of HIIT paradigm.
Exercise is associated with increased sympathetic
and decreased parasympathetic activity and the period
of recovery after maximum exercise is characterized
by a combination of sympathetic withdrawal and pa-
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rasympathetic activation. A mean extra resting heart
rate recovery of –5 bpm was observed 1 min after
cool-down in our patients. Heart rate recovery (HRR)
after strenuous exercise has been shown to be more
rapid among individuals with higher levels of fitness
and following aerobic training programmes in a variety
of adult and paediatric populations (31, 32). HRR is
thought to represent both the restoration of parasympa
thetic input and the withdrawal of sympathetic tone
after exercise; it may therefore be an indicator of
changes in fitness level and overall training status (33).
Increased vagal activity associated with a faster HRR
has been shown to be associated with a decrease in risk
of death (34). In a systemic view it was found that HRR
is considerably reduced after an aerobic exercise pro-
gramme in patients with established heart disease (35). It
was also demonstrated that HRR at 1–2 min recovery is
a prognostic measurement (36). Further study is required
to determine whether a mean extra reduction of 5 bpm
in patients with NSCLC is of physiological importance
with regards to a short-term rehabilitation programme.
The HRR in our patients did not improve between the
first and intermediate HIIT sessions, and the changes
were seen only for the final session in comparison with
the first session. In the later HIIT sessions the patients
were well accustomed to exercise and they were exer-
cising at higher intensities, with a significant increase in
HR session , dyspnoea and leg fatigue ratings. It is possible
that the HRR changes occurred at the end because of
the higher intensities of work, which demanded much
more cardio-respiratory effort, and also that a training
programme requires time to result in measurable chan-
ges. These findings also suggest that these deconditioned
patients may not have been able to reach their “true”
maximum aerobic capacity during the first CPET.
This study was performed with lung cancer patients
awaiting surgery. The study took advantage of this im-
portant time-window of opportunity to assess whether
exercise can have an important role in cardiorespiratory
fitness in such a short time, as well as motivating pa-
tients to play an active role in their well-being (5). A
systematic review of 18 pre-surgical exercise protocols
suggested functional and clinical benefits, which are
extremely important in cancer care, and pre-surgical
exercise can therefore be considered as a potential
adjuvant therapy (37). The American College of Sports
Medicine clearly states in its guidelines for cancer
survivors that exercise is safe in the pre-operative and
post-operative periods, and leads to improved physical
functioning and better quality of life (38).
The challenge in this trial was to maintain adherence
despite the fact that some patients had marked decon-
ditioning and highly sedentary levels. Twenty-two
percent of the patients had an ASA score of 3–4 (patient