1. Introduction and Purpose
SPRINT AND HIGH-INTENSITY INTERVAL TRAINING AND THEIR INFLUENCE ON RESTING METABOLIC RATE AND SUBSTRATE OXIDATION
Rebekah F. Seay, CSCS, EP-C, Holly E. Clarke, CSCS, EP-C, Katie K. Spain, and Matthew M. Schubert, PhD, CISSN, EP-C.
Department of Kinesiology, Auburn University at Montgomery, Montgomery, AL
Abstract
PURPOSE: Resting metabolic rate (RMR) and substrate oxidation have been linked with a number of health outcomes. Resistance training may increase metabolic rate while endurance training may help maintain metabolic rate with weight loss. However, the effects of high-intensity training on metabolic rate have not been closely examined. Therefore, the purpose of this investigation was to compare the effects of sprint and high-intensity training on RMR and substrate oxidation. METHODS: 22 (to date) men and women were assigned to either a sprint-interval training (SIT, n=8), high-intensity interval training (HIT, n=8), or a control condition (CON, n=6). Before and after 4 weeks of training, participants completed assessments for body composition, RMR, VO2max, energy intake, and physical activity. RESULTS: RMR and RQ did not statistically change in any of the groups. However, 67% of the participants in the experimental groups exhibited a change in RMR greater than 2x(TE), suggesting a meaningful change. Body mass did not change, though FM decrease by ~0.5 kg whilst FFM increased by ~0.5 kg in the experimental groups. VO2max did not significantly differ between groups, though HIT (+6.1%) and SIT (+11.6%) were greater after the intervention. CONCLUSIONS: Four weeks of interval training caused statistically non-significant but clinically meaningful changes in a number of variables. Studies with larger samples are needed to confirm these results.
Results
Table 2: Changes in Body Composition, Diet, and Activity
(Means ± Standard Deviation)
Figure: Top panels, pre/post changes in fasting RMR and RQ (Means ± Standard Deviation with individual participants
Bottom panels, change scores in fasting RMR and RQ for individuals; dashed lines represent 2x typical error of measurement (“true” response outside of technical/biological variation)
CONTROL
HIT
SIT
Body Mass (kg) Pre
82.8 ± 19.1
76.2 ± 16.2
76.0 ± 9.6
Body Mass (kg) Post
83.1 ± 18.9
75.7 ± 16.3
76.1 ± 9.5
Body Fat (%) Pre
20.8 ± 7.8
23.1 ± 9.0
25.0 ± 9.1
Body Fat (%) Post
21.0 ± 8.0
22.5 ± .2
23.8 ± 8.3
Fat Mass (kg) Pre
17.6 ± 9.6
17.8 ± 8.5
19.3 ± 8.5
Fat Mass (kg) Post
17.9 ± 9.8
17.3 ± 8.9
18.5 ± 7.9
Fat-free Mass (kg) Pre
65.2 ± 14.2
58.1 ± 13.4
56.6 ± 7.2
Fat-free Mass (kg) Post
65.2 ± 14.0
58.3 ± 13.2
57.5 ± 6.2
Waist Circumference (cm) Pre
79.0 ± 7.4
79.3 ± 7.8
81.8 ± 7.2
Waist Circumference (cm) Post
79.5 ± 7.0
79.1 ± 7.3
80.7 ± 7.2
Energy Intake (kcal) Pre
2584 ± 638
2360 ± 542
2350 ± 355
Energy Intake (kcal) Post
2544 ± 658
2391 ± 516
2359 ± 365
Sedentary time (%) Pre
61.9 ± 6.6
58.9 ± 7.8
62.6 ± 11.1
Sedentary time (%) Post
63.3 ± 5.9
57.5 ± 9.4
60.6 ± 10.6
Light PA (%) Pre
21.6 ± 2.5
25.3 ± 5.6
23.7 ± 6.7
Light PA (%) Post
20.9 ± 1.5
26.0 ± 5.6
25.4 ± 6.3
MVPA (%) Pre
16.5 ± 4.6
15.8 ± 3.5
13.7 ± 5.3
MVPA (%) Post
15.8 ± 4.6
14.0 ± 5.4
Steps per day Pre
12,378 ± 3,572
11,431 ± 3,023
9,498 ± 3,348
Steps per day Post
12,167 ± 3,773
12,307 ± 4,178
9,456 ± 2,825
Introduction and Purpose
Low volume, high-intensity interval training (HIT) has been promoted as a more time-efficient and similar or more potent stimulus than continuous moderate-intensity training (Gillen et al., 2016; Burgomaster et al., 2008; Gibala et al., 2012). HIT, and one of its relatives’ sprint-interval training (SIT, defined as “supramaximal” or Wingate-based training, (Weston et al., 2014)), have been shown to influence a number of health outcomes, including: cardiorespiratory fitness and maximal fat oxidation (Astorino et al., 2013a; Astorino et al., 2013b; Gist et al., 2014), changes in skeletal muscle proteins and markers of mitochondrial function (Gillen et al., 2013; Gurd et al., 2010; Little et al., 2010), reduced insulin resistance (Earnest et al., 2013; Little et al., 2011), and body composition (Gillen et al., 2013).
Despite all of these positive benefits, relative little attention has been given to the influence of interval training on resting metabolic rate and fasting substrate oxidation (Whyte et al., 2010; Sevits et al., 2013; Fisher et al., 2015; Martins et al., 2016). A low RMR has been linked with weight gain over time in some studies (Luke et al., 2006) but not others (Anthanont and Jensen, 2016; Shook et al., 2015), and Shook et al. reported that individuals with higher fasting respiratory quotients (RQ, a proxy of fasting substrate oxidation), indicative of a greater portion of carbohydrates being oxidized, gained larger amounts of weight than individuals with lower RQs (Shook et al., 2015).
Thus, the purpose of this study was to examine the influence of 4 weeks of SIT and HIT training on fasting RMR and RQ in healthy men and women.
Discussion
Primary findings:
-Statistically non-significant changes in RMR occurred in the two training groups
-HIT increased +2.5% and SIT by +3%
-5/8 participants in each group exhibited changes (increases) in RMR that were greater than 2x TE, indicative of a true response (Bonafiglia et al. 2016; Hopkins 2000)
-Statistically non-significant increases were also observed in VO2max and fasting percent macronutrient oxidation:
-SIT: +11.6% VO2max, -13.8% CHOOX, and + 7% FATOX
-HIT: +6.1% VO2max, -10.1% CHOOX, and + 4% FATOX
Acutely, IT has been reported to cause transient increases in RMR and decreases in RQ (Sevits et al. 2013; Kelley et al. 2013; Whyte et al. 2010). Importantly, these transient changes appear to dissipate within 48 hours, making the timing of assessment critical to ensure the most valid data are collected. Therefore, our window was ~72 hours after the participants’ last training session in order to minimize any transient effects of the IT bouts on RMR and RQ.
The handful of training studies to assess RMR in response to IT have generally reported no significant changes (Fisher et al. 2015; Martins et al. 2016). Data from the MET-1 exercise trial reported significantly increased RMR in women and men after a 16 month intervention (Potteiger et al. 2008). In contrast, the later MET-2 study reported no significant changes in RMR after 10 months of supervised aerobic exercise, despite substantial weight loss (Willis et al. 2014).
We acknowledge our limited sample (n=22) decreased our ability to detect significant differences between groups; we anticipate a total sample of by conclusion of data collection.
Contact:
Methods
Table 1: Changes in Fitness and Exercise Metabolism (Means ± Standard Deviation)
Healthy men and women were randomized to either a sprint interval training group or a high-intensity interval training group. Individuals who did not wish to complete the training but were interested in the results of testing self-selected into the control group. Individuals trained 3 days per week for four weeks. Heart rate, RPE, affect (Feeling Scale), and pain were assessed before and after each interval (within ~5 seconds).
The SIT group completed a modification of that previously described by Gillen et al. (PloS ONE 2016), consisting of 2 minute 10% Peak Power Output (PPO), 3x 20-second sprints at a resistance equivalent to 5% baseline body weight with 2 minute 10% PPO, and 3 minute cool 10% PPO. Week 2 increased to 4 sprints and weeks 3 & 4 incorporated 5 sprints. Total time per training session ranged from 10 minutes during week 1 to ~15 minutes during week 4.
The HIT group completed 1 minute 90% PPO with 1 minute 10% PPO with an equivalent warm-up and cool-down to the SIT group. 6 bouts were performed during weeks 1 & 2 and 8 during weeks 3 & 4. Total time per training session ranged from 16 minutes in week 1 to 20 minutes in week 4.
Before and after all training, subjects underwent tests for resting metabolic rate and substrate oxidation, maximal aerobic capacity and fat oxidation, body composition, a 3 day food record, and 7 days of wrist-worn accelerometry.
Data were analyzed in SPSS using repeated-measures ANOVA. To assess individual responses, the “true” response was determined from two times the typical error of measurement (Bonafiglia et al. PLoS ONE 2016)
CONTROL (n=6)
HIT (n=8)
SIT (n=8)
VO2max (mL∙kg-1∙min-1) Pre
37.5 ± 8.3
33.9 ± 10.1
36.0 ± 6.5
VO2max (mL∙kg-1∙min-1) Post
37.0 ± 8.8
36.1 ± 10.7
40.6 ± 8.9
Peak Power Output (W) Pre
235 ± 93
210 ± 66
225 ± 43
Peak Power Output (W) Post
238 ± 90
233 ± 61
248 ± 36
Maximal Rate of Fat Oxidation (g∙min-1) Pre
0.28 ± 0.13
0.24 ± 0.11
0.22 ± 0.08
Maximal Rate of Fat Oxidation (g∙min-1) Post
0.25 ± 0.14
0.25 ± 0.10
0.24 ± 0.12
Maximal Rate of Fat Oxidation (% of VO2max) Pre
42.5 ± 7.1
48.5 ± 9.0
39.6 ± 4.4
Maximal Rate of Fat Oxidation (% of VO2max) Post
41.0 ± 7.6
44.0 ± 7.4
36.2 ± 7.1