Titre de l’article : Impact de deux types d’entraînement par intervalles sur les déterminants de la performance
chez des hommes entraînés en endurance
Objectif : Comparer l’effet de l’entraînement par intervalles supramaximal et inframaximal à vélo sur les
déterminants de la performance chez des hommes entraînés en endurance.
Méthodes : La consommation maximale d’oxygène (VO2max), la puissance maximale atteinte durant le test
d’effort progressif (Pmax), la puissance aérobie maximale (PAM) et la capacité anaérobie ont été mesurés
avant et après un programme d’entraînement par intervalles de 6 semaines (3 séances par semaine) inframaximal (85 % PAM, fractions d’effort de 1 à 7 min, ratio effort:repos de 2:1, EPI85, n = 8) ou
supramaximal (115 % PAM, fractions d’effort de 30 sec à 1 min, ratio effort:repos de 1:2, EPI115, n = 9) menés
jusqu’à épuisement, chez des hommes entraînés en endurance (VO2max = 55,9 ± 4,9 ml/kg/min avant
l’entraînement).
Résultats : Le volume d’entraînement était 47 % inférieur dans le groupe EPI115 comparativement au groupe
EPI85 (304 ± 77 vs 571 ± 200 min; p < 0,01). Le VO2max a augmenté de 6,3 % tant dans le groupe EPI115
(55,9 ± 4,0 vs 59,2 ± 1,1 ml/kg/min, p < 0,05) que dans le groupe EPI85 (56,0 ± 6,0 vs 59,3 ± 4,7 ml/kg/min,
p < 0,05). L’augmentation du VO2max était inversement corrélée avec le VO2max de départ dans le groupe
EPI115 (r = -0,962, p < 0,01), mais pas dans le groupe EPI85. La Pmax a augmenté seulement dans le groupe
EPI85 (+4,5 ± 1,9 %, p < 0,01), alors que la capacité anaérobie s’est améliorée seulement dans le groupe
EPI115 (+5,7 ± 7,1 %, p < 0,05).
Conclusions : L’entraînement par intervalles supramaximal et inframaximal permettent tous les deux
d’améliorer le VO2max chez des cyclistes entraînés. L’entraînement par intervalles supramaximal peut être
Impact of two interval training intensities on key performance factors in endurance-trained men Submission type: original investigation
Myriam Paquette1,2, Olivier Le Blanc1,2, Guy Thibault1, Patrice Brassard1,2
1Department of Kinesiology, Faculty of Medicine, Université Laval, Québec, Canada
2Research center of the Institut universitaire de cardiologie et de pneumologie de Québec, Québec, Canada
Corresponding author:
Patrice Brassard, Ph.D.
Department of Kinesiology, Faculty of Medicine PEPS - Université Laval
2300 rue de la Terasse, room 2122 Québec (Qc) GIV OA6, Canada Phone: 418 656-2131 extension 5621
Fax: 418-656-4908
Email: patrice.brassard@kin.ulaval.ca
Preferred running head: Infra- and supramaximal interval training Abstract word count: 238
Text-only word count: 3418 Number of tables: 2 Number of figures: 2
ABSTRACT
Purpose: To compare the effects of supramaximal and inframaximal cycling interval training on key endurance performance factors in moderately endurance-trained men.
Methods: Maximal oxygen consumption (VO2max), peak power output reached during a ramp exercise
protocol (Ppeak) and sprint performance (peak and mean anaerobic power) were measured before and after 6
weeks (3 sessions/week) of either inframaximal (85% maximal aerobic power [MAP], 1- to 7-min effort bouts, 2:1 work:rest ratio, HIT85, n = 8) or supramaximal (115% MAP, 30-s to 1-min effort bouts, 1:2 work:rest ratio,
HIT115, n = 9) interval training to exhaustion in moderately endurance-trained men (VO2max = 55.9 4.9
ml/kg/min).
Results: High-intensity training volume was 47% lower in HIT115 compared to HIT85 (304 77 vs 571 200
min; p < 0.01). VO2max increased by 6.3% in both HIT85 (from 56.0 6.0 to 59.3 4.7 ml/kg/min) and HIT115
(from 55.9 4.0 to 59.2 1.1 ml/kg/min, all p < 0.05). Increase in VO2max induced by training was strongly
and inversely related to baseline VO2max in HIT115 (r = -0.962, p < 0.01) but not HIT85. Ppeak increased only in
HIT85 (+4.5 1.9%, p < 0.01) and anaerobic capacity increased in HIT115 only (+5.7 7.1%, p < 0.05).
Conclusion: Both supramaximal and inframaximal interval training can improve aerobic capacity in moderately endurance-trained men. Supramaximal interval training might be interesting for subjects who wish to improve both aerobic and sprint capacity.
INTRODUCTION
In endurance sports such as cycling, maximal oxygen consumption (VO2max), endurance capacity, anaerobic
fitness and movement efficiency are key performance factors1. For endurance athletes, who already have a
high fitness level, increasing the volume of continuous submaximal training is usually not sufficient to further improve performance2. High-intensity interval training (HIT), that consists in “repeated short-to-long bouts of
rather high-intensity exercise interspersed with recovery periods”3 is usually considered as the most effective
training regimen to improve performance in trained and untrained subjects4.
Inframaximal interval training, characterized by the repetition of effort bouts at intensities below VO2max, is
efficient in improving performance in highly trained cyclists5-7. There is accumulating evidence that sprint
interval training (SIT), which consists in performing a small number of all-out sprints (typically 4 to 10 sprints) of short duration ( 30 s), interspersed with long recovery bouts (typically 2 to 4 min), may increase aerobic capacity. Two recent meta-analyses revealed that SIT have a small-to-moderate8 or moderate9 effect on
aerobic capacity. However, Weston et al.9 meta-analysis reveals an unclear effect of SIT on aerobic capacity
among athletic men.
In physically active but not endurance-trained subjects, six weeks of supramaximal running interval training (7- 12 bouts of 20 to 30 s at 130% of 3000 m time trial speed) provided greater benefits for concurrent improvement in endurance, sprint and repeated sprint performance than inframaximal interval training (4-6 bouts of 4 min at 3000 m time trial speed)10. It is unknown which of the two intensity domains, supramaximal or
inframaximal interval training, provides the greatest benefits in endurance-trained athletes, given the unclear effect of SIT on aerobic capacity in that population.
A few studies have compared inframaximal or maximal and supramaximal interval training in endurance- trained athletes11-13 with mixed results. A study from Stepto et al.13 suggests that improvements in cycling
endurance performance is maximal with HIT performed at 85% Ppeak (i.e., inframaximal interval training) and
175% Ppeak (SIT), compared to HIT performed at 80%, 90% or 95% Ppeak. However, studies from Esfarjani et
al.11 and Laursen et al.12 suggest that interval training at VO2max have a greater effect than SIT on aerobic
capacity in athletes.
Therefore, the aim of the present study was to assess the impact of inframaximal and supramaximal interval training on key endurance performance factors in moderately endurance-trained adults. It is expected that, in an endurance-trained population, inframaximal interval training would have a greater impact on aerobic capacity compared to supramaximal interval training. However, supramaximal interval training would be associated with a greater increase in sprint performance.
METHODS Subjects
Nineteen moderately endurance-trained men (27 7 years, 72 10 kg) volunteered to participate in this study. Subjects were road cyclists (n = 9), triathletes (n = 7), mountain bikers (n = 2) and cross-country skier (n = 1), who were training at least 4 times a week in the months before the study. This study was approved by the local ethics committee according to the principles established in the Declaration of Helsinki, and all subjects provided written informed consent.
Design
Subjects reported to the laboratory on four different occasions over a period of two weeks to perform: 1) resting measurements, 2) a progressive ramp exercise protocol to determine VO2max and Ppeak, 3) a maximal
aerobic power (MAP) stepwise intermittent protocol and 4) a Wingate test to assess sprint performance (peak and mean anaerobic power). Subjects were asked to refrain from training for at least 12 hrs and to avoid alcohol and caffeine consumption for 24 hrs before each visit. After preliminary evaluation, subjects were divided into two interval training groups: inframaximal (HIT85) or supramaximal (HIT115). These four tests were
repeated 48 to 96 hrs following the end of the 6-week training program.
Methodology
Resting measurements. Height and body weight were measured in each subject. Lean mass and percent
body fat (%BF) were assessed using a bioimpedance body composition analyser (InBody520, Biospace, CA, USA). Subjects then rested supine during 10 min. Heart rate (ECG monitoring), arterial pressure and cardiac output using pulse contour analysis14 (Nexfin, Edwards Lifesciences, Ontario, Canada) were continuously
monitored on a beat-by-beat basis during the resting period and the last 5 min of recording was averaged to represent baseline.
Ramp exercise protocol. VO2max was determined using an electromagnetically braked cycle ergometer
(Corival, Lode, the Netherlands). The ramp incremental protocol started with 1 min of unloaded pedalling followed by 30 W/min increments until volitional fatigue. Expired air was continuously recorded with a breath- by-breath gas analyser (Breezesuite, MedGraphics Corp., MN, USA) for the determination of VO2, carbon
dioxide production (VCO2), minute ventilation (VE) and respiratory exchange ratio (RER: VCO2/VO2). Heart rate
(HR) was obtained from ECG monitoring and blood pressure was measured at rest and every two minutes during the test using an automated sphygmomanometer with a headphone circuit option (Model 412, Quinton Instrument, Bothell, WA, USA). The gas analyser was calibrated before every test using a certified gas mixture and the gas volumes were calibrated before every test using a 3-L syringe. VO2max was defined as the
during the test and maximal HR (HRmax), VE (VEmax), respiratory rate (RRmax) and RER (RERmax) were defined
as the highest values recorded, or calculated, during the test. The ventilatory threshold (VT) was determined using the V-slope method15. The respiratory compensation point (RCP) was determined using the criteria of an
increase in ventilatory equivalents for O2 and CO2 concomitant to a decrease in end-tidal partial pressure of
CO216.
Maximal aerobic power test. Percentage of MAP was used in this study to prescribe training intensity. In
order to determine the power output of the first stage of the MAP test, predicted MAP (MAPP) was calculated
from the VO2max reached during the ramp protocol using the following equation: VO2 (ml/min) = (power output
[W] x 6 kpm/W) x 2 ml/kpm + 30017. Therefore, MAPP (W) = (VO2max (ml/min) – 300)/12. Subjects performed
the MAP test on the same cycle ergometer as the ramp protocol. An intermittent test with 5-min stages was used (Figure 1). Cadence was freely chosen throughout the test. MAP was defined as the power output of the last stage completed or the power output of an uncompleted stage where VO2 increased by > 150 ml/min
compared to the previous completed stage. The cumulated time of exercise (excluding warm-up and recovery phases) during the MAP test (TMAP) was used as an index of endurance. VO2, HR and blood pressure were
monitored as previously described during the ramp protocol.
Cycling efficiency. Gross mechanical efficiency (GME, %) was used to assess cycling efficiency. GME was
defined as the ratio of mechanical work output to energy input18, where: mechanical work output (kgm) =
Power output (W) x time (sec) x 0.102 kgm/j and energy input (kgm) = VO2 (L/min) x 4.838 kcal/L (thermal
equivalent) x 426.4 kgm/kcal. For calculation of GME, data was collected during the fifth min of the warm-up of the MAP test.
Sprint performance. Peak and mean anaerobic power were assessed using a 30-s Wingate Anaerobic test.
The test was performed on an electronic cycle ergometer (Velotron, RacerMate, Seattle, WA, USA). Before the Wingate test, subjects performed a 10-min warm-up at 150 W or 50% MAP (for subjects with a MAP < 300 W) with 5-s non-maximal sprints every min during the last 5 min. Subjects were allowed a 2-min resting period before starting the test. The test was preceded by a 2-s unloaded acceleration. The load was then set to 9.4% of subjects’ body weight, who were asked to attain a peak power as quickly as possible and to continue to exercise maximally for the duration of the sprint (30 s), while remaining seated. Peak anaerobic power (peak power/body weight) and mean anaerobic power (mean power/body weight) were calculated.
Training interventions. Subjects were paired for age and VO2max and assigned to one of the two training
groups (HIT85 or HIT115). Training consisted of 3 HIT sessions per week over a period of 6 weeks, with 48 to
72 hrs between sessions. On remaining days, subjects were asked to avoid high intensity exercise, but to maintain a similar low and/or moderate intensity training volume as before study entrance. The HIT85 group
effort time of active recovery (150 W or 50% MAP if MAP < 300 W) until exhaustion. The HIT115 group
performed repeated 30-s to 1-min effort bouts, depending on the session, at 115% MAP, separated by twice the effort time of active recovery (150 W or 50% MAP if MAP < 300 W) until exhaustion.
For both training protocols to be comparable, subjects were asked to exercise until exhaustion, defined as the inability to complete an effort bout. Subjects were asked to rate their level of fatigue using the modified Borg scale (0 to 10) right after every training session. After 3 weeks of training, subjects’ MAP was measured to adjust training intensity for the 3 remaining weeks. Total HIT volume was calculated for each subject, using the number of repetitions performed and the length of the effort bouts of every session.
Statistical analysis
Statistical analyzes were performed using SPSS statistical software, version 19.0 (Statistical Package for Social Science, IL, USA). A Student’s t Test for independent samples was used to examine the differences between groups before training. A Student’s t Test for paired samples was used in each group to assess whether each specific interval training protocol had an effect on the dependent variables. As well, repeated- measures ANOVAs (intra-subject factor: time; inter-subject factor: group) were used to compare changes in the dependent measures between groups. When groups differed for pretraining values, an ANCOVA was used (dependent variable: pre-posttraining difference; covariate: baseline value)19. Tukey’s post hoc tests were used
when appropriate. Association between baseline VO2max and change in VO2max with training was examined
using linear regression. The significance level was set at p < 0.05. All data are presented as mean standard deviation.
RESULTS
Data from one subject in each group were removed from the analysis due to illness or excessive fatigue during the training regime precluding evaluations completion. Therefore, 8 subjects in HIT85 and 9 subjects in HIT115
completed the study. At baseline, subjects in both groups had similar age (HIT85: 26 6 yrs, HIT115:
27 6 yrs), height (HIT85: 1.77 0.08, HIT115: 1.78 0.08 m), body weight, %BF and VO2max (Tables 1 and
2).
Training characteristics. HIT training volume was 47% less in HIT115 than HIT85 (304 77 vs 571 200 min;
p = 0.007). Subjects from both groups attended 16 training sessions on average during the 6 weeks (p = 0.79). Subjects from HIT85 and HIT115 rated respectively 9.5 0.3 and 9.3 0.6 (p = 0.50) in average on the modified
Borg scale after the training sessions.
Resting measurements. Data from resting measurements before and after training are presented in Table 1.
for systolic blood pressure and heart rate. Resting diastolic blood pressure increased in HIT115 but not HIT85.
Training decreased resting HR in HIT85 (-5 3 bpm, p < 0.01), but not HIT115.
Key performance factors. The repeated measures ANOVA revealed no time x group interaction for any
performance variable. Key performance factors before and after training are shown in Table 2.
Ramp exercise protocol. Figure 2 shows individual changes in VO2max (L/min and ml/kg/min) in HIT85 and
HIT115 with training. Both HIT85 (p = 0.02) and HIT115 (p = 0.04) improved VO2max relative to weight (ml/kg/min)
by 6.3% with training, but only HIT85 improved absolute VO2max (L/min) (Table 2). Ppeak reached during the
ramp protocol increased only in HIT85 (+4.5 1.9%, p < 0.01). Before training, VT was at 52% VO2max in both
groups. Increase in VO2 at VT in HIT85 approached statistical significance (p = 0.08). VO2 at RCP increased in
both HIT85 (p < 0.01) and HIT115 (p = 0.02), but power output at RCP increased only in HIT115 (+9.4%,
p = 0.04). HRmax, RERmax, VEmax and RRmax as well as HR and power output at VT were unchanged after
training in both groups.
As VO2max at baseline was variable within each group, linear regression between VO2max at baseline and the
change in VO2max with training in each group was performed. In HIT115, there was a strong negative
relationship between baseline VO2max and the change in VO2max with training (r = -0.962, r2 = 0.926,
p < 0.01). This relationship was not statistically significant, yet still moderate to large, in HIT85 (r = -0.621,
r2 = 0.368, p = 0.10).
MAP and TMAP.MAP (+1.6%, p = 0.03) and TMAP (+33%; p < 0.01) increased only in HIT85 (Table 2).
Cycling efficiency. GME was higher in HIT85 compared to HIT115 before and after training. Cycling efficiency
decreased in HIT85 (p = 0.04) and was unchanged after training in HIT115 (Table 2). Mean cadence during
GME measurement was similar before and after training in both groups (HIT85: 95 2 vs 95 4 rpm, p = 0.82;
HIT115: 93 7 vs 93 6 rpm, p = 0.92).
Sprint performance. Peak anaerobic power was higher in HIT115 compared to HIT85 (p = 0.02) before the
training intervention. After training, mean anaerobic power was increased only in HIT115 (+4.9%, p < 0.05).
Peak anaerobic power was unchanged after training in both groups (Table 2).
DISCUSSION
The novel finding of this study is that supramaximal interval training is as much effective as inframaximal interval training in improving VO2max (ml/kg/min) in moderately endurance-trained men following a 6-week
training period, but with half the cumulated time spent at target intensity. Also, if both inframaximal and supramaximal training can increase aerobic capacity, only supramaximal training is associated with an increase in sprint performance.
VO2max. VO2max is the primary determinant of endurance performance1. In this study, VO2max (ml/kg/min)
increased by ~6% in both groups. Previous studies have shown that inframaximal interval training can improve VO2max in already endurance-trained subjects5,6. In recent meta-analyses, SIT was found to have a small-to-
moderate effect on VO2max, leading to a ~8%8 or 4.2-13.4% increase in VO2max20. Weston et al. (2014)9
meta-analysis also suggests a moderate improvement in VO2max following SIT (3.6-10.0% increase) in
sedentary or active non-athletic subjects when compared with controls. However, their meta-analysis revealed an unclear effect of SIT on the VO2max of athletic men. Our study suggests that supramaximal interval training
can increase VO2max in an endurance-trained population. However, baseline VO2max in our study (56.0 6.0
ml/kg/min) was lower than in some studies included in the meta-analysis.
In our study, the increase in VO2max with training was inversely related to pretraining VO2max for
supramaximal training, which is in line with a meta-analysis revealing that SIT “have an apparent adaptive effect on VO2max that favours the less fit”9. It suggests that supramaximal training will benefit more the less fit
athletes, while more fit endurance athletes might still benefit from inframaximal training.
Endurance, VT and RCP. Endurance performance was not assessed in this study. However, the time before
exhaustion in the MAP test (TMAP) was used as an index of endurance. TMAP increased following inframaximal,
but not supramaximal training in this study. VO2 at which VT occurs relates to the %VO2max that can be
sustained during a long-term effort, and therefore, to endurance21. Improvement in VT following inframaximal
training approached statistical significance in our study, also suggesting a possible effect of inframaximal training on endurance, although further study is needed to confirm this observation. Interestingly, power output at RCP is strongly related to time-trial performance in trained cyclists22, suggesting that the 9.4% increase in
RCP following supramaximal training in our study may be accompanied by a similar increase in endurance performance.
Peak power output. Ppeak increased following inframaximal but not supramaximal training in this study. The
4.5% increase in Ppeak following inframaximal training is in line with results from various studies where 3 to 6
weeks of interval training at 80-85% Ppeak in trained cyclists increase Ppeak by 3-5%7,13. Ppeak, measured during
a 25-W increment progressive test or a ramp exercise protocol, accounts for 70-90% of the performance variation during 16.1-km to 40-km time trials23,24. However, the increase in Ppeak following a training intervention
is not related to the improvement in time-trial performance following interval training in cyclists7,13. Stepto et
al.13 found that SIT increased 40-km time-trial performance as much as training at 85% Ppeak, but without an
increase in Ppeak. Laursen et al.12 found a greater increase in Ppeak and VO2max after training at 100% Ppeak
when compared to SIT, but changes in average speed during a 40-km time-trial was not different between groups. These observations suggest that there is more than one mechanism responsible for improvement in
cycling performance following HIT. It also suggests that the increase in performance following supramaximal training could be as important as following inframaximal training even if increases in Ppeak were not significant.
Cycling efficiency. Cycling efficiency is related to endurance performance, as cyclists with a higher efficiency
can generate a greater power output for the same VO225. GME has been reported to be in the range of 18-
23%25, which is in line with our results (GME: 17.2-22.6%). Previous studies have shown that HIT (above
onset of blood lactate accumulation)26 and strength training27 can slightly improve cycling efficiency in
competitive cyclists. Surprisingly, cycling efficiency did not change following supramaximal training, and decreased by 2.9% (from 21.5% to 20.9%) following inframaximal training in our study. Stöggl et al. found no reduction in submaximal VO2 after a 9-week HIT program at 90-95% HRmax in highly trained elite runners,