Fig 1.
Flow chart depicting the recruitment process leading to the final training group sample sizes.
Out of 155 initial expressions of interest, forty-five healthy, moderately-active men met the inclusion criteria and volunteered to participate in the study. During the preliminary testing phase, fifteen participants withdrew for various reasons (e.g. changes in availability, time commitment, and for personal reasons). Thirty participants completed the baseline testing and were allocated to one of the three training groups. During the training phase, one participant withdrew due to an injury sustained outside of the study. Therefore, twenty-nine participants completed the training study and were included in the final analyses. HIIT high-intensity internal training; DNC did not complete.
Fig 2.
Schematic overview of the study.
HIIT high-intensity interval training; RT resistance training only; HIIT+RT high-intensity interval training and resistance training group; RT+HIIT resistance and high-intensity interval training group; whey protein (0.25 g.kgBM-1); DXA dual-energy x-ray absorptiometry; 1-RM one repetition maximum;
peak aerobic power; FAM familiarisation trial; BASE baseline trial; “PRE” mean of FAM2 and BASE trials; MID mid-training trial; POST post-training trial.
Table 1.
Baseline characteristics of each training group.
Data are mean ± SD.
Fig 3.
Percent changes in strength and power indices after 5 (MID) and 9 (POST) weeks of training.
(A) Peak CMJ displacement, (B) velocity, (C) force, (D) power, and (E) leg press 1-RM strength. Data are adjusted group means (solid dash), plus unadjusted individual percent changes. The trivial region was determined from the smallest worthwhile change for each variable (0.2 × combined between-subject baseline SD). a/A = within-group difference vs PRE; b/B = between-group difference vs RT at same time point; c/C = between-group difference vs HIIT+RT at same time point. Capital letters denote effects that remained clear after adjustment for multiple comparisons.
Table 2.
Between-group comparisons of changes in all performance measures, from PRE-to-MID and PRE-to-POST training.
Data are mean percent differences and 90% compatibility intervals (±90%CI), plus magnitude-based decisions of standardised effect sizes (ES) and qualitative likelihoods†.
Fig 4.
Percent changes in body composition and aerobic fitness after 5 (MID) and 9 (POST) weeks of training.
(A) Total lean mass, (B) total fat mass, (C) relative , (D) lactate threshold, and (E) peak aerobic power. Data are adjusted group means (solid dash) with unadjusted individual percent changes. The trivial region was determined from the smallest worthwhile change for each variable (0.2 × combined between-subject baseline SD). a/A = within-group difference vs PRE; b/B = between-group difference vs RT at same time point; c/C = between-group difference vs HIIT+RT at same time point. Capital letters denote effects that remained clear after adjustment for multiple comparisons. N.B. due to an equipment fault at the time of testing, PRE-to-MID changes are unavailable for 2 participants in HIIT+RT (
), and one from RT (
).
Table 3.
Average weekly training loads (both internal and external), and average “readiness-to-train” (RTT) scores for the prescribed training sessions (mean ± SD).