Public health practitioners and researchers in behavioral medicine recognize the need
to find effective physical activity interventions and prescriptions to curb the growth
in inactivity and prevent chronic illness (Conn et al., 2009; Hagger, 2010; Hardcastle
et al., 2012; Katzmarzyk and Lear, 2012). For example, researchers in exercise physiology
have focused on the minimal dose of exercise needed to gain favorable physiological
adaptations to cardiovascular and metabolic systems (Gibala et al., 2012). Efforts
to identify a minimal dose of exercise are linked to the problem of exercise adherence
with few people meeting current physical activity guidelines of 30 min per day of
moderate intensity exercise. Given that time is the most commonly cited barrier to
exercise (Trost et al., 2002; Sequeira et al., 2011), exercise professionals have
focused attention on the development of time-efficient exercise interventions (Gibala,
2007). A recent development is the advocacy of Sprint Interval Training (SIT) as a
means to attain substantial health benefits with a lower overall exercise volume.
SIT is characterized by repeated, brief (4–6 × <30 s), intermittent bursts of all-out
exercise, interspersed by periods (approximately 4.5 min) of active or passive recovery
(Gibala et al., 2012). Research has consistently demonstrated that participation in
SIT results in a host of physiological adaptations including improvements in health
and fitness indicators (Burgomaster et al., 2006, 2008; Gibala et al., 2006, 2012;
Rossow et al., 2010; Tong et al., 2011). In addition, these improvements have been
reported to be equal or superior to traditional continuous aerobic training despite
SIT involving a substantially lower total overall training volume (Rossow et al.,
2010; Tong et al., 2011; Gibala et al., 2012; Cocks et al., 2013). Consequently, SIT
is being advocated as a time-efficient alternative intervention for the achievement
of fitness and health benefits through exercise (Gibala, 2007; Whyte et al., 2013).
In this article we contend that SIT is unlikely to be taken up by the majority of
the sedentary population and caution is needed before such training is advocated to
the general public. Proponents of SIT have focused almost exclusively on physiological
adaptations. However, the exclusive focus fails to consider whether a largely sedentary
population will feel physically capable and sufficiently motivated to take up and
maintain a regime of highly intense exercise. Based on theory and research in exercise
psychology, we contend that the prospect of participating in SIT for previously sedentary
individuals is likely to be considered too arduous and may evoke anticipated perceived
incompetence, lower self-esteem, and potential failure (Williams and Gill, 1995; Hein
and Hagger, 2007; Lindwall et al., 2011). They may likely be more inclined to avoid
participating as a consequence. We also contend that should previously sedentary individuals
be introduced to high intensity exercise of the type proposed in SIT it will likely
evoke a high degree of negative affect that may lead to an avoidant response with
the prospect of future sessions. In addition, we contend that SIT is a complex and
structured regime that requires high levels of self-discipline and self-regulation
and is, therefore, unlikely to be adopted outside the laboratory environment (Hagger,
2013; Hagger and Luszczynska, 2014). Finally, we debate the notion that SIT is time-efficient
and suggest that it does not sufficiently address “lack of time” as a commonly-cited
barrier to exercise (Hardcastle and Hagger, 2011).
In a largely sedentary population, the strenuous nature of SIT is likely to be a deterrent
to participation because individuals tend to avoid exercise if they find it aversive.
Several theories including social cognitive theory (Bandura, 1977), achievement motivation
theory (Weiner, 1985) and self-determination theory (Deci and Ryan, 1985; Hagger et
al., 2006; Chatzisarantis et al., 2007) contend that a high level of motivation and
competence are needed to participate in regular physical activity. Typically, sedentary
and low-active individuals do not feel competent in the physical domain and may not,
therefore, feel sufficiently confident to engage in the activity (Teixeira et al.,
2012). The motivation and effort required to participate in high intensity exercise
is much higher than that needed to undertake activities of a moderate intensity (e.g.
walking) (Williams and Gill, 1995; Tritter et al., 2013). If individuals feel unable
to demonstrate competence in SIT, they are more likely to invest little effort in
a prescribed activity or avoid it all together. Low competence, self-esteem, and motivation
among sedentary individuals are a considerable problem for exercise promoters presented
with the task of developing means to promote increased activity to a resistant population
(Williams and Gill, 1995; Hein and Hagger, 2007).
In addition to competence and motivation, enjoyment is also a predictor of exercise
adherence and most people do not enjoy high intensity exercise (Parfitt and Hughes,
2009). SIT may be inappropriate for a largely sedentary population because the negative
affect that such supra-threshold intensities evoke could diminish intrinsic motivation
and discourage exercise adherence. There is considerable evidence that adherence to
exercise is influenced by affective responses to exercise intensity. In particular,
enjoyment and feelings of pleasure have been shown to decrease as exercise intensity
increases (Ekkekakis et al., 2011). The American College of Sports Medicine (ACSM)
exercise guidelines state that exercise-induced feelings of fatigue and negative affect
can act as a deterrent to continued participation (American College of Sports Medicine,
2013). The supra-threshold intensities induce a psychobiological stress response that
is felt as unpleasant. Conversely, exercise intensities below these thresholds can
be effective for improving health and fitness and are generally rated as more pleasant,
and more likely to be tolerated by, most individuals irrespective of age or physical
condition. In a study on sedentary adults' adherence to exercise prescriptions, Perri
et al. (2002) found significantly greater adherence in the moderate intensity condition
compared to the high intensity condition. Prescribing a higher frequency (5–7 days
vs. 3–4) of exercise sessions increased the accumulation of exercise without a decline
in adherence, whereas prescribing a higher intensity decreased adherence and resulted
in the completion of less exercise over the 6 months. Although some studies have found
SIT to be more enjoyable than continuous exercise (e.g., Bartlett et al., 2011), they
have tended to focus on “recreationally active” participants meaning that the findings
cannot be directly applied to an unfit and sedentary population. In addition, recent
research has focused on strategies to reduce the negative affect experienced by individuals
when performing SIT such as listening to music or receiving feedback to boost self-efficacy
(e.g., Tritter et al., 2013; Stork et al., 2014). However, we contend that such endeavors
are futile given that such types of training are unlikely to be adopted or maintained
by sedentary individuals in the first place.
SIT is also inappropriate for a largely sedentary population because it is a relatively
complex and structured exercise regime that requires a high degree of self-regulation
to be effective. Mostly SIT protocols have been undertaken in laboratory settings
under the supervision of exercise physiologists (e.g., Gibala et al., 2006; Burgomaster
et al., 2008; Cocks et al., 2013; Whyte et al., 2013) not to mention the “significant
encouragement provided during the Wingate tests” by the research team (Cocks et al.,
2013, p. 645). The transfer of SIT to an unsupervised setting in which the onus is
placed on inexperienced sedentary individuals to self-select the appropriate intensity
is likely to be problematic. Individuals will need to know the speed and effort required
to work during the supra-maximal and active recovery periods. They will also require
self-monitoring tools at hand such as a stopwatch to time the intervals, and will
also need to have sufficient know-how to undertake an appropriate warm up and cool
down to prevent injury. It is unlikely that sedentary individuals with low levels
of experience with exercise are going to be able to be independently successful in
a complicated activity like SIT. Further research is needed to explore whether the
SIT can be successfully implemented and maintained in a real life setting with those
insufficiently active and unfamiliar with vigorous intensity exercise.
Finally, we question the often-cited benefit of SIT that it is time-efficient. If
the minimal number of intermittent bursts of activity is four followed by four 4.5
min breaks, then at least 20 min is needed and this does not include a warm up or
cool down. Therefore, in reality individuals would still need to free up 30 min in
order to participate, even if on fewer days of the week (three as opposed to five).
For sedentary individuals, a time-efficient means to engage in a programme of regular
physical activity and structure it around a busy lifestyle is attractive. However,
coupled with other concerns about the adverse psychological effects of high-intensity
exercise regimens like SIT, and their relative complexity to undertake, we contend
that lower intensity bouts of exercise of a similar duration are likely to be more
appealing to sedentary individuals. Exercise of this nature may, therefore, be optimally
effective in promoting adherence to exercise in this population.
In summary, we contend that although SIT appears to be an effective exercise modality
for physiological benefit, it is unlikely to be effective as a means to promote regular
participation in physical activity in a largely sedentary population. We have argued
that SIT is inappropriate for sedentary individuals because engaging in such training
requires high levels of motivation and confidence. In addition, high intensity exercise
is likely to evoke to negative affect which may lead to subsequent avoidance of further
exercise. SIT programmes of exercise are also relatively complex and involve a high
degree of self-regulation, which may also be a barrier to continuation in those who
are uninitiated. Finally, we contend that SIT should not necessarily be considered
time efficient as a session would likely last at least 30 min. We would like to see
further research that addresses the motivational factors and responses of sedentary
people to SIT. Specifically, we propose the following research agenda to improve knowledge
of SIT in sedentary populations: (1) the acceptability of, and affective responses
to, SIT programmes; (2) the social cognitive and motivational factors that may be
related to participation in, and adherence to, SIT programmes; (3) the degree of adherence
to SIT programmes compared to programmes of continuous aerobic exercise of moderate
intensity; and (4) whether SIT programmes can be transferred to natural settings outside
of the supervised laboratory environment.
Author contributions
Sarah J. Hardcastle conceived the ideas presented in the article and took the lead
role in drafting the article. Hannah Ray, Louisa Beale, and Martin S. Hagger assisted
in drafting the article.
Conflict of interest statement
The authors declare that the research was conducted in the absence of any commercial
or financial relationships that could be construed as a potential conflict of interest.