Baseline VO2peak: Extraversion effect

Background and rationale

  • WHO guidelines recommend healthy adults accumulate at least 150 minutes of activity per week (physical activity, n.d.).
  • Despite recommendations, only about 22.5% of adults and 19% of adolescents worldwide meet these goals (Guthold et al., 2018).
  • Physical inactivity is a growing risk factor for physical and mental health concerns across the lifespan (Farooq et al., 2020).
  • Understanding how personality traits relate to physical activity engagement may help tailor interventions and improve uptake and adherence.
  • Prior literature: Big Five traits linked to activity engagement and performance in athletic contexts; extraversion and conscientiousness often relate to higher activity, neuroticism to anxiety and inactivity; findings often come from cross-sectional self-reports with limitations in recall bias.
  • Gaps addressed by this study: objective fitness measures, longitudinal design, and examination of personality as a predictor of engagement in a home-based exercise program and its outcomes.

Aims and hypotheses

  • Primary aims: (i) identify relationships between personality and baseline fitness; (ii) determine whether personality influences enjoyment of exercise by intensity; (iii) determine whether personality predicts outcomes of a home-based 8-week training program.
  • Hypotheses (as stated): extraversion, neuroticism, conscientiousness, and agreeableness would relate to outcomes; openness would not.
  • Expected patterns: extraversion and conscientiousness positive associations with fitness and activity; neuroticism related to lower engagement and enjoyment; openness not related to engagement or enjoyment.

Methods

Participants and design

  • Recruited from the general public via newsletters and social media.
  • N = 132 at baseline testing (56 female).
  • Matched randomization into two groups by age, birth sex, BMI, and VO2max (V̇O2peak): intervention (n = 78) and control (n = 54).
  • 86 participants completed the entire protocol (control n = 25; intervention n = 51).
  • Dropouts reasons: illness (n = 2), surgery (n = 3), and unavailability/loss of contact (n = 41).
  • Ethical approval: University College London Research Ethics Committee (13985/004). Informed consent obtained.

Measures

  • Online pre-intervention questionnaires: demographics, Perceived Stress Scale-10 (PSS-10), and a modified Big Five Inventory-10 (BFI-10).
    • PSS-10: 10-item perceived stress scale. Cronbach’s alpha typically 0.65–0.93.
    • BFI-10: 10-item Big Five with 2 items per trait; a third Agreeableness item added to improve measurement (loading 0.89 in this sample).
    • Note: BFI-10 Cronbach’s alpha reported in literature ranges 0.14–0.71; acceptable test–retest reliability and correlates with BFI-44.
  • Baseline testing (lab): body composition by bioelectrical impedance; VO2peak; strength tests; lab low-intensity session; post-baseline testing included.
  • Primary trial outcomes: VO2peak, anaerobic threshold, peak power output, heart rate recovery, press-ups, plank time, body fat percentage, and weekly hours of physical activity.
  • Stress measurement at two timepoints: PSS-10 at baseline and post-intervention.
  • Enjoyment ratings: after each training session in week 1 (1–7 scale) for both lab tasks and home-based sessions.
  • Randomized trial with a home-based 8-week cycling + strength program vs. resting control with weekly 10-minute stretching plan for control (not monitored).

Exercise interventions and testing protocol

  • Lab assessments and testing order (Figure 1): lab sessions including low-intensity cycling, VO2peak ramp test, and post-test recovery.
  • Lab low intensity session (single occasion): 15 minutes cycling at RPE 4/10, on a stationary cycle; HR and gas exchange monitored.
  • VO2peak test: ramp protocol after 3 minutes of loadless cycling; workload increased by 15 or 25 W/min depending on training level; cadence kept 60–70 rpm; no verbal encouragement; test terminated at volitional exhaustion or cadence <60 rpm for 30 s or two 45 s windows. Recovery: 3 minutes at 25 W; HR recovery (HRR) computed as HR change from max to 120 s into recovery, i.e., HRR=HR<em>extmax−HR</em>120s.HRR = HR<em>{ ext{max}} - HR</em>{120s}.; VO2peak and peak RER determined from smoothed data (7-breath average).
  • Thresholds: ventilatory thresholds (VT1, VT2) derived from VO2peak test to set individualized five heart-rate zones for training via Polar Flow/Beat app.
  • Training zones and sessions (8 weeks):
    • Easy long ride: 50 minutes at zone 2 (HR around VT1-to-VT2 vicinity; zone 2 relative to VT1).
    • Threshold ride: variable intensities with 15 minutes in zone 2, 5 minutes in zones 3–4, and 5 minutes in zone 2.
    • HIIT ride: 10 minutes in zone 2 plus 4 × 2 minutes at maximal effort with 2 minutes active recovery, and 5 minutes in zone 2.
    • Strength session: bodyweight exercises (squats, lunges, press-ups, sit-ups, calf raises, glute bridges) 3 sets × 8 reps; progression/regression provided to target an RPE of 8/10.
  • Progression: intensity gradually increased across the 8 weeks; participants logged enjoyment after each aerobic and strength session.
  • Control condition: maintain usual lifestyle; no monitoring beyond weekly 10-minute stretching plan for engagement.

Data analysis

  • Software: RStudio; normality checked with Shapiro–Wilk.
  • Non-parametric analyses used due to non-normal distribution of personality traits.
  • Group comparisons: independent t-tests or Mann–Whitney U tests.
  • Primary analyses: pre–post changes via mixed-model ANOVA; relationships via backward-elimination multiple linear regressions; logistic regressions for adherence predictors.
  • Full models included all five personality traits + age + gender; model simplification by backward elimination using AIC until p < 0.05 for remaining predictors.
  • Significance threshold: ext{p} < 0.05.
  • Outcomes reported with effect sizes where provided (e.g., R2<em>adjR^2<em>{adj}, partial eta-squared η</em>p2\eta</em>p^2).
  • Tables referenced: Table 1 (baseline demographics), Table 2 (means, SDs, correlations), Table 3 (baseline fitness regressions), Table 4 (enjoyment regressions), Table 5 (pre–post changes by group).

Key findings

Demographics and baseline fitness by sex

  • Sample at baseline: 132 participants (56 female).
  • Baseline differences (sex): females had higher body fat percentage (p < 0.001), lower VO2peak (p < 0.001), lower peak power output (p < 0.001), and fewer push-ups in 60 s (p < 0.001).
  • Personality differences by sex: females scored higher than males on extraversion (p = 0.035), agreeableness (p < 0.001), neuroticism (p = 0.002), and openness (p = 0.041).
  • Age correlations: age positively correlated with conscientiousness (p = 0.001) and negatively correlated with neuroticism (p < 0.001).

Baseline relationships between personality and fitness

  • Extraversion significantly predicted higher baseline VO2peak, anaerobic threshold, and peak power output:
    • VO2peak: $$p = 0.006,\