Methodological Considerations
The strengths of this study include a between-within subjects
randomized repeated-measures design, which allows
for firm conclusions to be made when comparing the effects
of ACT versus implementation intention on exercise
behavior and enjoyment. To our knowledge, this is the first
study to assess the effects of ACT in comparison to implementation
intentions on long-term exercise behavior and
enjoyment. Furthermore, the current study followed the
women for 6-months, which is the longest follow-up exercise
data that results from a brief ACT intervention. Despite
these strengths, the study has a number of limitations
to be considered. First, the study does not include an objective
measure of exercise behavior and/or cardiorespiratory
fitness. The self-report measure used to assess exercise
(Godin-Leisure Time Questionnaire), however, was
selected because it has been shown to significantly correlate
with objective measures (e.g., Caltrac® accelerometer)
of physical activity (Miller et al. 1994). Further, the participants
were aware that the follow-up contact was aimed to
assess their levels of exercise participation. As such, we
cannot preclude the possibility that both groups’ selfreports
of increased physical activity participation and enjoyment
at follow-up were influenced by social desirability.
Nevertheless, the influence of social desirability should
have affected both groups equally in this randomized parallel
group study. Moreover, efforts were made to select an
exercise activity self-report measure that is valid, reliable
and responsive to both short- and long-term interventions
(e.g., Mistry et al. 2015). Furthermore, although ACT was
compared to a well-established and highly effective technique
- implementation intentions - the present study did
not compare ACT to a wait-list control group. Thereby,
general external factors (e.g., environmental variables)
cannot be ruled out as influencing the increase in exercise
behavior and enjoyment in both groups. This study provides
important initial findings that ACT is comparable to
implementation intentions in increasing exercise behavior
and enjoyment over a period of 6-months. Future research,
however, needs to examine the magnitude of the effectiveness
of ACT when compared with a wait-list control condition
and to make firm conclusions about the effectiveness
of ACT in promoting long-term physical activity.
Conclusions
To address the wide-ranging barriers to physical activity, it
may be essential for health promotion efforts to create innovative
approaches that target physical inactivity. Specifically,
alternative interventions should be personalized in order to
maximally increase exercise and enjoyment. Although more
research is needed to better understand the effects of ACT in
promoting long-term physical activity participation and enjoyment,
the notable findings of our study provide preliminary
evidence that ACT may be as effective as implementation
intentions at increasing long-term exercise activity and enjoyment
among low-active women. Given that the overwhelming
majority of adults do not engage in the recommended minimum
amount of daily physical activity, it is important to identify
multiple approaches of encouraging physical activity participation
and enjoyment (Colley et al. 2011; Warburton et al.
2006). This study was a first step in establishing that ACT
may be as useful as other well established techniques in promoting
physical activity in initially low-active women. Future
directions may include evaluating ACT in promoting physical
activity in a more representative sample of the general population
(including men), overweight and obese adults, elderly
adults, and clinical populations such as patients with chronic
diseases (e.g., diabetes, coronary artery disease, emphysema,
etc.). In addition, evaluations of which personality characteristics
distinguish individuals who may respond more favorably
to ACT techniques versus implementation intention interventions
needs to be further examined, as well as their additive
benefits on physical activity.
Compliance with Ethical Standards
Ethical Approval All procedures performed in studies involving human
participants were in accordance with the ethical standards of the
institutional and/or national research committee and with the 1964 Helsinki
declaration and its later amendments or comparable ethical
standards.
Informed Consent Informed consent was obtained from all individual
participants included in the study