Effect of Exercise Intensity, Duration and Mode on Post ... - Google Sites

Sports Med 2003; 33 (14): 1037-1060 0112-1642/03/0014-1037/$30.00/0

REVIEW ARTICLE

 Adis Data Information BV 2003. All rights reserved.

Effect of Exercise Intensity, Duration and Mode on Post-Exercise Oxygen Consumption Elisabet Børsheim and Roald Bahr Norwegian University of Sport and Physical Education, Oslo, Norway

Contents Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1037 1. Excess Post-Exercise Oxygen Consumption (EPOC) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1038 2. Early Studies on EPOC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1039 3. Methodological Considerations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1039 4. Effect of Intensity and Duration of Aerobic Exercise on EPOC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1040 5. Effect of Split Exercise Sessions on EPOC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1047 6. Effect of Supramaximal Exercise on EPOC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1048 7. Effect of Aerobic Exercise Mode on EPOC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1048 8. Effect of Resistance Exercise on EPOC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1049 9. Effect of Training Status on EPOC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1051 10. Effect of Sex on EPOC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1052 11. Possible Mechanisms for the Rapid EPOC Component . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1053 12. Possible Mechanisms for the Prolonged EPOC Component . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1053 13. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1056

Abstract

In the recovery period after exercise there is an increase in oxygen uptake termed the ‘excess post-exercise oxygen consumption’ (EPOC), consisting of a rapid and a prolonged component. While some studies have shown that EPOC may last for several hours after exercise, others have concluded that EPOC is transient and minimal. The conflicting results may be resolved if differences in exercise intensity and duration are considered, since this may affect the metabolic processes underlying EPOC. Accordingly, the absence of a sustained EPOC after exercise seems to be a consistent finding in studies with low exercise intensity and/or duration. The magnitude of EPOC after aerobic exercise clearly depends on both the duration and intensity of exercise. A curvilinear relationship between the magnitude of EPOC and the intensity of the exercise bout has been found, whereas the relationship between exercise duration and EPOC magnitude appears to be more linear, especially at higher intensities. Differences in exercise mode may potentially contribute to the discrepant findings of EPOC magnitude and duration. Studies with sufficient exercise challenges are needed to determine whether various aerobic exercise modes affect EPOC differently. The relationships between the intensity and duration of resistance exercise and the magnitude and duration of EPOC have not been deter-

1038

Børsheim & Bahr

mined, but a more prolonged and substantial EPOC has been found after hardversus moderate-resistance exercise. Thus, the intensity of resistance exercise seems to be of importance for EPOC. Lastly, training status and sex may also potentially influence EPOC magnitude, but this may be problematic to determine. Still, it appears that trained individuals have a more rapid return of post-exercise metabolism to resting levels after exercising at either the same relative or absolute work rate; however, studies after more strenuous exercise bouts are needed. It is not determined if there is a sex effect on EPOC. Finally, while some of the mechanisms underlying the more rapid EPOC are well known (replenishment of oxygen stores, adenosine triphosphate/creatine phosphate resynthesis, lactate removal, and increased body temperature, circulation and ventilation), less is known about the mechanisms underlying the prolonged EPOC component. A sustained increased circulation, ventilation and body temperature may contribute, but the cost of this is low. An increased rate of triglyceride/fatty acid cycling and a shift from carbohydrate to fat as substrate source are of importance for the prolonged EPOC component after exhaustive aerobic exercise. Little is known about the mechanisms underlying EPOC after resistance exercise.

1. Excess Post-Exercise Oxygen Consumption (EPOC) During exercise, there is an increase in oxygen ˙ 2) to support the increased energy need. uptake (VO ˙ 2 does not return to resting levels After exercise, VO immediately, but may be elevated above resting levels for some period of time. Originally, the in˙ 2 after exercise was explained by the creased VO oxygen debt hypothesis. The theoretical basis for this was formulated by Hill et al.[1-4] They hypothe˙ 2 after exercise was necessised that the elevated VO sary for the repayment of the oxygen deficit incurred after the start of exercise, and ascribed the oxygen debt to the oxidative removal of lactate. Margaria et al.[5] modified the concept, and suggested that the oxygen debt consisted of a lactacid component caused by glycogen synthesis from lactate, and an alactacid component related to other factors. The lactacid component was considered to be the slower component. However, the causality implied by the term ‘oxygen debt’ is contrary to what is currently known about the biochemical mechanisms underlying the increase in metabolism post-exercise. Therefore, Gaesser and Brooks[6] introduced the causality  Adis Data Information BV 2003. All rights reserved.

neutral term ‘excess post-exercise oxygen consumption’ (EPOC), which also includes the more pro˙ 2 that may be observed for longed increase in VO hours after exercise. EPOC consists of several components.[6,7] In this review, the term ‘rapid component’ will be used to describe the sum of components that decays within approximately 1 hour, whereas the prolonged component decays monoexponentially with a half-life in the order of several hours (figure 1). Therefore, processes active also beyond the first hour postexercise must be responsible for the prolonged EPOC component. Training (i.e. repetitive bouts of exercise) may also have a more chronic effect on resting metabolic rate (RMR). In particular, this seems to be the case in trained compared with untrained individuals, especially when combined with high/sufficient energy intake, resulting in a high energy flux or turnover.[8] At times it may be difficult to separate this effect from the EPOC effect. In this review, we will only ˙ 2 after an acute bout of exerinclude studies of VO cise. Sports Med 2003; 33 (14)

EPOC and Exercise Intensity and Duration

1039

200

EPOC (mL/min)

150

100

50

0 0

2

4

6

8

10

12

Later, more controlled studies have been performed. Some studies have confirmed that there is ˙ 2 after exercise that may last for an increase in VO several hours.[14-19] However, other studies have concluded that EPOC is transient and minimal after exercise.[20-24] The conflicts in the results may be resolved if differences in exercise intensity and duration are taken into account, since this may be expected to affect the metabolic processes underlying EPOC. Also, differences in exercise mode, training status and sex may potentially contribute to the discrepant findings.

Time after exercise (h) Fig. 1. Time plot of excess post-exercise oxygen consumption (EPOC) after exhaustive submaximal exercise (71–80 minutes at 69–78% of maximal oxygen uptake; n = 12). The solid line shows the prolonged EPOC component (reproduced from Bahr,[7] with permission).

2. Early Studies on EPOC The first report on an elevated RMR after physical activity was published by Benedict and Carpenter in 1910.[9] They observed a mean increase in RMR of 11.1% for their two study participants during sleep in a respiration calorimeter 7–13 hours after severe exercise. Initially it was thought that ˙ 2 contributed signifipost-exercise elevation in VO cantly to the energy cost of exercise, and would be an important factor in daily energy expenditure. ˙ 2 of five Herxheimer et al.[10] noted that the VO untrained individuals did not return to baseline until 36–48 hours after exercise, and Edwards et al.[11] reported a 25% elevation in metabolism 15 hours after cessation of 2 hours of strenuous football. Also, Passmore and Johnson[12] found a 15% increase in RMR for 7 hours after a 16km walk at 6.4 km/hour in three males, and deVries and Gray[13] found a 10% increase in RMR for 6 hours after 1 hour of mixed aerobic exercise. However, in many cases, the intensity and duration of exercise was not quantified in these early studies, and they provided minimal information about the controls. Also, they did not account for other factors that may influence RMR, such as time of day, prior uncontrolled exercise, food, temperature, caffeine intake, habituation and stress.  Adis Data Information BV 2003. All rights reserved.

3. Methodological Considerations There are several methodological issues that are important to consider when studying EPOC. Accurate control over the pre-experimental conditions, and an excellent reproducibility in the indirect calorimetry measures are prerequisites to be able to detect small, but potentially important differences. Only few authors report the precision of the indirect ˙ 2. The calorimetry system used to measure VO Douglas bag method is generally considered to be the most accurate method of expired gas analysis, but few authors, especially of newer studies, have used this technique. Instead, automated systems have been used, often with unknown validity and reliability. Furthermore, the pre-experimental conditions have not always been well controlled. The study participants should have a stable weight, and food intake and exercise should be controlled. It is also advisable for study participants to sleep overnight in the laboratory before a study to avoid exercise in the morning; however, an outpatient protocol may give no different values than an inpatient protocol when the conditions are controlled and the study participants are transported to the laboratory.[25,26] Also, habituation of the study participants to testing procedures is of utmost importance. The experimental conditions both before and during measurements need to be strictly controlled. For female study participants, it may also be necessary to control for menstrual cycle differences. Sports Med 2003; 33 (14)

1040

When reviewing even the newer EPOC literature, it is a problem that the methods for measuring baseline and EPOC duration are inconsistent among investigations. In some studies, a separate control study has been used to control for time effects, whereas others have used only one pre-exercise value as baseline. In many studies, only 30 minutes ˙ 2 of rest in the morning has been used and the VO during the final 10 minutes of this has been taken as baseline for EPOC. This can lead to falsely high ˙ 2 baseline values in the morning, since a certain VO increase because of anticipation may be expected, which subsequently leads to an underestimation of EPOC. In some cases, the baseline and recovery data have been collected with the individuals in a seated position, in others in a recumbent position. The RMR is lower in recumbent position, probably because it is difficult to avoid fidgeting and relax completely when sitting for an extended period. This results in a greater measurement error and a reduced ability to detect differences between the baseline and recovery conditions. Different methods have also been used to deter˙ 2 has returned to resting levels. Some mine when VO ˙ 2 continuously, whereas others have measured VO have measured at discrete time points. Furthermore, ˙ 2 until it has returned to some have measured VO resting values, others only for a pre-determined time period. Finally, because of inter-individual variability in EPOC, it is important with a high enough number of study participants to be able to detect differences. 4. Effect of Intensity and Duration of Aerobic Exercise on EPOC ˙ 2 after Table I contains a review of studies on VO aerobic exercise. The absence of a sustained in˙ 2 after exercise seems to be a consistent crease in VO finding in studies with low exercise intensity and/or low exercise duration. No EPOC was found beyond 35 minutes of recovery after 5 or 20 minutes cycling at 50%, 65%, and 80% of maximal oxygen uptake ˙ 2max),[20] beyond 40 minutes of recovery after (VO 20–40 minutes of treadmill exercise around the ven Adis Data Information BV 2003. All rights reserved.

Børsheim & Bahr

tilatory threshold,[21] and beyond 40 minutes after 4 × 20 minutes of cycle ergometry at 35–55% of ˙ 2max.[22] Only two males and two females took VO part in the last study. Brehm and Gutin[23] found a relationship between EPOC and the intensity of walking/running, but their intensity was still low, the highest being 11.3 km/hour in trained individuals. After 3.2km running at this intensity, EPOC amounted to only 71kJ (~3.5L oxygen). Elliot et al.[24] also found a short lasting (7h

Rest position not reported. NC

1963

2M

Cycling, bench step, run/walk: 45 min (effective time 25 min)

~1.9L (57 kcal)

NC

Knuttgen[28]

1970

5F, 7M

Cycling: 45–98%, 15–55 min

≤5L, duration NA

Bed rest. NC. EPOC magnitude related to intensity and duration

Segal & Brooks[29]

1979

11M

Cycling: 55 and 95%, 2 min

≤4L, duration NA

Seated. NC. EPOC magnitude related to intensity

Hagberg et al.[20]

1980

18M

Cycling: 50%, 65% and 80%, 5 and 20 min

≤5L, duration NA

Moderate cycling (used as base-line). NC. EPOC measured for 15 min

Hermansen et al.[30]

1984

1M

Cycling: 75%, 80 min

˙ 2↑ 12h EPOC: 48L. At 24h: VO 5.9%

Bed rest. C

Bielinski et al.[14]

1985

10M (T)

TM: 50%, 3h

RMR↑ 9% for 4.5h. At 18h: RMR↑ 4.7%

Seated/respiratory chamber. C. Food given 30 min postexercise

Pacy et al.[22]

1985

2F, 2M (T)

Cycling: 35–55% for 20 min × 4 (40 min break)