1 INTRODUCTION
1.5 Study Aim and Hypotheses
The primary aim for the current study was to investigate the possibility that cognitive control mediates the widely-observed PA-emotional health association in health young adults. To achieve this aim, regular PA, cognitive control, and emotional functioning were assessed in a cross-sectional sample of healthy young adults. In light of known interrelationships among sleep, PA, cognitive performance, and emotional functioning (reviewed in Dishman et al., 2006), a measure of sleep quality was also assessed to allow for statistical control. Regular PA was es- timated using both self-reported PA and aerobic fitness data. The construct of cognitive control was measured using neutral and emotional versions of the classic Flanker and Stroop tasks, performance on which has been shown to be affected by PA (Guiney & Machado, 2013), and emotional functioning (Kanske, 2012). Emotional functioning was assessed through self-report of current levels of depression, anxiety, and stress.
Given research evidence that regular PA affects brain structures and functions impli- cated in implementing the cognitive processes engaged during cognitive control, a core expec- tation was that regular PA would be positively linked not only with emotional health, but also with cognitive control performance in the present study. The novel question of interest was whether cognitive control would mediate the regular PA-emotional functioning relationship in young adults. More specifically, it was hypothesized that level of regular PA would indirectly in- fluence emotional functioning through its effect on cognitive control, indexed by separate com- posites of neutral and emotional interference effects. Further, it was expected that there would be larger effects when the cognitive control task had emotional stimuli (emotional composite), compared to neutral stimuli (neutral composite). This expectation was grounded in the idea that the inclusion of emotional processing requirements would increase cognitive control demands, as well as in earlier findings that emotional cognitive control is more tightly related to emotional functioning than is neutral cognitive control. Hypotheses focused specifically on response time and interference effects during cognitive control tasks because, in the extant literature, PA level/fitness does not typically correlate with accuracy on cognitive control tasks in young adults (Guiney & Machado, 2013). In addition, because most researchers have conducted task-spe- cific performance analyses, rather than generating composites of multiple task performances, exploratory mediation analyses were also conducted using task-specific interference effects as the mediator.
Possible findings from the current study were anticipated to help 1) clarify the associa- tions between regular PA and performance on cognitive control tasks in young adults, 2) provide further understanding of cognitive mechanisms that might link regular PA and emotional health, and 3) guide future decisions about PA recommendations based on the processes that benefit from regular PA.
Table 1. Aerobic exercise and cognitive control studies (Stroop & Flanker tasks)
Task Study Ages N Exercise type or
measures De- sign Results Behavioral p CHILDREN Flanker Letter Hillman et al. 2009
8-11 38 Aerobic fitness (PACER test) CS Compared low-fit (bottom 10 %ile), high-fit (top 10 %ile) children showed:
Higher accuracy rates across conditions and following commission errors * Flanker Arrow Chaddock et al., 2010a
9-10 55 Aerobic Fitness (VO2 max
test)
CS Compared low-fit (<30 %ile), high-fit (>70 %ile) children showed:
Smaller Flanker effects based on proportional interference scores * Flanker Arrow with neutral tri- als (fish) Voss et al., 2011
9-10 36 Aerobic Fitness (VO2 max
test)
CS Compared low-fit (<30 %ile), high-fit (>70 %ile) children showed:
Higher accuracy rates, particularly on incongru- ent trials (greater accu- racy costs) * Flanker Arrow Pontifex et al., 2011; Wu et al., 2011
8-11 48 Aerobic Fitness (VO2 max
test)
CS Compared low-fit (<30 %ile), high-fit (>70 %ile) children showed:
Higher accuracy rates, and less variable re- sponse latencies *** Flanker Arrow Chaddock et al., 2012
9-10 32 Aerobic Fitness (VO2 max
test) CS Compared low-fit (<30 %ile), high-fit (>70 %ile) children showed: Maintenance of accu- racy rates, particularly on incongruent trials across test blocks
*
Stroop Buck et al., 2008
7-12 74 Aerobic Fitness (PACER test)
CS Association be- tween aerobic fit- ness and:
Items reported in 45 sec and
Interference effect
* n.s. Stroop Castelli et al.
2011
7-9 59 Aerobic exercise (vari- ous)- 75 min/day, 5 days/week, 9 months
RUT Association be- tween increased aerobic fitness and:
Items reported in 45 sec n.s.
YOUNG ADULTS Flanker
Letter
Themanson & Hillman, 2006
~20 28 Aerobic Fitness (VO2 max
test)
CS Compared to low fit, high fit (>80th
%ile) showed:
Table 1. Aerobic exercise and cognitive control studies (Stroop & Flanker tasks)
Task Study Ages N Exercise type or
measures De- sign Results Behavioral p Flanker Arrow Themanson, Pontifex, & Hill- man, 2008
18-25 62 Aerobic Fitness (VO2 max
test)
CS Association be- tween VO2 max and:
Greater post-error accu- racy when instructed to maximize accuracy * Flanker Arrow with Neutral tri- als Winneke, Godde, Reuter, Vieluf, & Voelcker-Re- hage, 2012 35-48 & 55- 65 49 Self-reported PA (Ger- man version of the Baecke Activity Ques- tionnaire)
CS Compared to low active, high active showed:
Smaller Flanker effects on incongruent condi- tion in the younger mid- dle-aged group only
*
Stroop Hwang & Cas- telli, 2015
10-30 93 Cardiorespiratory fit- ness
CS Association be- tween fitness and:
Smaller interference ef- fects
Stroop Dupuy et al., 2015
19-34 22 Aerobic Fitness (VO2 max
test)
CS Compared to low fit, high fit showed:
Faster RT on incongru- ent trials
* OLDER ADULTS
Stroop Dustman et al., 1984
55-70 13 Aerobic exercise (brisk walking) 60 min/day, 3 days/week, 4 months
RCT After training, aero- bic exercise group showed: Reduced interference *** Flanker Letter Kramer et al., 2001
60-70 58 Aerobic exercise (brisk walking) 3 days/week, 6 months, compared to nonaerobic stretching and toning
RCT After training, aero- bic exercise group showed:
Smaller Flanker effects *
Flanker Arrow
Colcombe et al., 2004 Study 1
55+ 41 Aerobic Fitness (VO2 max
test, Rockport Test)
CS Compared to low fit, high fit (median split) showed:
Smaller Flanker effects (% increase in RT) * Flanker Arrow Colcombe et al., 2004 Study 2
58-77 29 Aerobic Exercise (walk- ing): 40 min/day, 3 days/week, 6 months
RCT After training, aero- bic exercise group showed:
Smaller Flanker effects (11% RT reduction) * Flanker Letter Hillman, Belo- polsky, Snook, Kramer & McAuley (2004) ~67 24 Self-reported PA (Yale Survey for Older Adults)
CS Comparison of low, moderate, and high fit showed:
No differences in RT or accuracy
Table 1. Aerobic exercise and cognitive control studies (Stroop & Flanker tasks)
Task Study Ages N Exercise type or
measures De- sign Results Behavioral p Flanker Arrow Hillman et al., 2006
15-71 241 Self-reported PA that in- duced sweating
CS Association be- tween fre-
quency/week and:
Faster RT across all ages; Smaller Flanker effects in > 40 years old
**
Stroop Smiley-Oyen et al., 2008
64-74 28 Aerobic exercise (brisk walking)
30 min/day, 3 days/week, 10 months
RCT After training, aero- bic exercise group showed: Less interference Improved Accuracy *** ** Flanker Letter Voelcker-Re- hage et al., 2010
62-79 72 Aerobic Fitness (VO2 max
test)
CS Association be- tween VO2 max and:
RT on incompatible tri- als
**
Stroop Prakash et al., 2011
60-75 70 Aerobic Fitness (VO2 max
estimate, Rockport test)
CS Association be- tween VO2 max and:
Less interference Higher accuracy * ** Flanker Letter Voelcker-Re- hage et al., 2011
62-79 44 Aerobic exercise (brisk walking), compared to relaxation and stretch- ing, 3 times/week, 12 months
RCT After training, aero- bic exercise group showed:
Improved accuracy after 12 months * Stroop Weinstein et al., 2012 Mean: 66.6
124 Aerobic Fitness (VO2 max
test)
CS Association be- tween VO2 max and:
Less interference * Stroop Gajewski &
Falkenstein, 2015
65-87 40 Self –reported history of long-term PA: high ac- tive, low active
CS Long term PA is as- sociated with:
Reduced interference *
Note. CS = cross-sectional; RCT = randomized controlled trial; LS = longitudinal study; PA = physical activity; VO2max = maximal oxy-
gen uptake; RT = response time; proportional interference scores = percent increase in RT to incongruent stimuli, over and above the average RT to congruent stimuli; n.s. = not significant
* = p < .05. ** = p < .01 *** = p < .001
2 METHODS