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Response to constant and interval exercise protocols in the elderly.

INTRODUCTION

Traditionally, exercise protocols of intensity and duration have been determined for a broad and general population and then extrapolated or modified for other populations, such as the at-risk aged population. Regular physical activity is known to reduce the risk factors of chronic disease and disability and the aging process is known to correlate with a reduction in physical activity, which further reinforces the need for exercise protocols for the elderly that are not only efficient but also beneficial. Reductions in V[O.sub.2] max in non-endurance trained individuals are thought to be associated with the decrease in lean muscle mass that occurs with ageing (5).

Fitness professionals and coaches have generally avoided using interval training due to concerns regarding the increase in heart rate (HR) and respiratory stress of which both are constant during steady-state cardiovascular training. However, with recent research supporting the use of interval training for increased cardiovascular effect (6,20), patients with COPD (2,19) and fat oxidation (16), exercise physiologists may need to reconsider its use in at-risk populations. The aging population is one such group of people who are looking for ways to maintain good health and who are interested in participating in a range of conditioning activities to promote their health (13).

It is well known that the mode of exercise influences physiological responses, with differences found between a single continuous exercise protocol and three different intermittent exercise protocols (10). Intermittent training protocols at both 50% and at 70% of V[O.sub.2] Peak showed significantly lower HR, minute ventilation ([V.sub.E]), and V[O.sub.2] when compared to a similar amount of work done within constant load protocols. This thinking suggests that intermittent training is more efficient than constant load training. However, HR, [V.sub.E], and V[O.sub.2] were taken at the mid-point of each stage of exercise, meaning that the total expired gas, HR, and energy expenditure for the duration of the exercise were not examined. A similar finding was made when comparing constant walking and high- intensity interval walking with the latter resulting in greater increases in V[O.sub.2] Peak (11).

As high-intensity interval walking helps to protect older persons against some of the age-related reductions in muscle strength and V[O.sub.2] Peak, it may also be valuable for the exercise prescription to encourage a high-intensity component during walking in the elderly. For the sedentary aged population, the problems of joint degeneration and the associated high ground force impact from walking may inhibit this mode of physical activity. Consequently, the low impact and simple nature of cycle ergometers are often preferred by people with orthopedic disabilities of the lower extremities, which are more prevalent in elderly people than younger populations.

The purpose of this study was to examine the physiological responses in the elderly using cycle ergometers across two different protocols, constant and interval. It is anticipated that the findings will help exercise physiologists understand exercise training in the elderly (1).

METHODS

Subjects

Sixteen subjects (10 males aged 69.2 [+ or -] 3.7 yrs, height 173.7 [+ or -] 7.1 cm, weight 85.2 [+ or -] 16.7 kg, and BMI 28.0 [+ or -] 3.9 with a predicted V[O.sub.2] max of 36.6 [+ or -] 4.9 emLkg-1[min.sup.-1], and 6 females aged 66.2 [+ or -] 3.2 yrs, height 163.4 [+ or -] 6.4 cm, weight 69.3 [+ or -] 7.9 kg, and BMI 26.2 (4.4) with a predicted V[O.sub.2] max of 32.8 [+ or -] 5.1 mLkg-1[min.sup.-1] volunteered to participate in this study. The participants were informed of the research risks and all signed the University Human Ethics approved consent forms before the data were collected.

Procedures

All the subjects were currently participating in a minimum level of activity per week of 90 min. They were able to use a cycle ergometer unaided. Additionally, the subjects were not on any medications that might interfere with physical activity. The subjects were classified in the 'moderate' category through the risk stratification process (12). All subjects were tested on three separate mornings, having fasted overnight each time and refrained from strenuous exercise and activity on the preceding day to testing. The first session involved a pre-exercise screening questionnaire (12), a 20-min supine resting 12-lead electrocardiogram (ECG) and a submaximal fitness assessment. The 12-lead ECG placement was consistent with standard protocol (14). Subjects rested in the supine position for 20 min, after which a sample ECG was taken and assessed for any abnormalities.

The subjects engaged in a submaximal V[O.sub.2] test to predict their V[O.sub.2] max. The test was performed on an electronically braked cycle ergometer (Jaeger ER800, Bitz, Germany). The test commenced with the subjects cycling at 60 r[min.sup.-1] for 2 min at 20 W. The resistance was then increased to 50 W for 2 min and, then, an additional 25 W every subsequent 2 min until each subject's HR reached 75% of age-predicted maximal HR, using the formula 208 - [0.7 x age](17) or until each subject was unable to continue to pedal at 60 r[min.sup.-1]. Maximum oxygen consumption was calculated by extrapolation using the Multi-stage Model (18). The values were then used to calculate the percent effort protocol for the constant and interval exercise sessions that were randomly held on the second and third morning exercise sessions. Heart rate was measured via the ECG throughout the testing sessions. Subsequent to each of the two exercise sessions, the participants completed another resting 12-lead ECG as part of the post exercise assessment process.

Expired gas samples were collected via a one-way re-breather mask (Hans-Rudolph 7930 breathing valve, Kansas City, MO) and analyzed using a calibrated TrueMax 2400 metabolic measurement system (Parvo Medics, Sandy, UT). The system was calibrated prior to the start of each session according to standard operating manual procedures. The data were sampled continuously but reported every 15 sec as averages for that period (5). The data were categorized into five different phases: (I) resting baseline; (II) warm-up; (III) exercise; (IV) cool-down; and (V) post-exercise resting. Baseline values were collected with participants seated on the cycle ergometer at rest. This was followed by the warm-up, which consisted of 2 min of 60 r[min.sup.-1] pedalling at 20 W. The exercise phase involved 20 min of pedalling at 50% of extrapolated V[O.sub.2] max for the constant session, or 20 min of alternating intensity equal to 70% V[O.sub.2] max for 1 min followed by 1 min of 30% V[O.sub.2] max in the interval session. The subjects were asked to indicate their RPE using the 6 to 20 Borg scale (3) after each min of exercise in the exercise phase. The cool-down involved 2 min at 20 W, and the postexercise collection phase was 20 min of supine resting. All protocols for the two exercise sessions, pre- and post-exercise, were identical with the exception of the exercise phase of the session.

Statistical Analyses

The data were analyzed using a one-way analysis of variations (ANOVA), and reported as means with 95% confidence intervals, upper and lower bounds where applicable. Changes in effect statistics are presented in raw and percentage changes. One-way repeated ANOVA for all physiological responses showed there were no significant differences between gender, therefore the results are presented as n = 16. The threshold for statistical significance was set at P < 0.01.

RESULTS

Mean values for all responses between the two protocols for all subjects as shown in Table 1 were found to have no statistically significant differences. Total V[O.sub.2] for the 42-min period from exercise to post-exercise was 28.07 Liters for constant and 29.40 Liters, respectively. The effect statistics showed that the interval protocol was greater for volume of [O.sub.2], volume of C[O.sub.2], and ventilatory equivalent values for all phases.

Figure 1 presents the V[O.sub.2] comparisons between the two protocols averaged in 15-sec intervals. Heart rates during the interval protocol changed by approximately 10 beats x [min.sup.-1] between the effort at 70% and the recovery at 30% V[O.sub.2] max with a gradual increase over the 20- min exercise phase, which is similar to that of the constant protocol that showed an increase of ~10 beats x [min.sup.-1] over the course of the 20-min period.

[FIGURE 1 OMITTED]

Mean HR presented in Table 2 showed no significant differences between the two protocols with relative differences in HR less than 1.2% in both the exercise and the post- exercise phases. Respiratory exchange ratios (RER) and respiratory rates (RR) did not vary significantly between phases except for the 2-min cool-down phase RER, which showed a statistically significant difference (P = 0.05).

Average RPEs for both exercise phases of the two protocols were almost identical with the constant session mean RPE of 11.4 and the interval session mean RPE of 11.3. This average is consistent with an RPE just above the 'light' level of exertion in both protocols.

Correlations reported as moderate (R = 0.4 to 0.7), strong (R = 0.7 to 0.9), and excellent (R > 0.9). Height and weight showed strong correlations with post-exercise V[O.sub.2] for constant, but not the interval protocol. Similarly, cool-down and post-exercise [O.sub.2] usage showed moderate correlations with constant and not interval. Post-exercise RER showed moderate correlations with both V[O.sub.2] max and [O.sub.2] usage during the exercise phase in interval, but not in constant. The pattern and strength of correlations were similar for most other measures.

DISCUSSION

The purpose of this study was to determine the physiological responses in the elderly using cycle ergometers across two different protocols, constant and interval. Oxygen consumption during the exercise phase of the interval protocol was 16% higher, when compared to the constant exercise protocol. This difference was not statistically significant. Further differences were noted during the cool-down (5%) and the post-exercise phases (2%). This specific at-risk population has not been investigated in published research for these two protocols and yet, although not significant the increase in the physiological measures support the previously reported advantages of interval training for increased cardiovascular effect in a younger adult population (6,20). Gender was found not to influence the physiological responses, which is also similar to previous research (4).

VC[O.sub.2]

For VC[O.sub.2] there were also differences in favor of interval protocol with an increase during the exercise phase of 18.7 %, during the cool-down phase of 7.7%, and the post-exercise phase of 1.2%. Whilst there are no significant differences between these figures the effect statistic suggests that interval protocol elicits greater energy expenditure during the exercise phase using more [O.sub.2] and producing more VC[O.sub.2]. Thus interval training for the elderly may accumulate a greater response or training effect if performed over a period of time instead of a single bout as done in this study. However, the confidence interval for the both exercise and cool-down phases show these results varied with upper and lower limits more than 100% from the mean suggesting the range of response may still be quite varied and individual dependent.

EPOC

Considering EPOC (cool-down + post-exercise period 22 min) as a percentage of total (exercise + cool-down + post-exercise period 42 min) oxygen consumption during the two exercise sessions, the outputs were similar at 23.33% and 23.27% for the constant and interval sessions respectively. When reporting EPOC as a percentage of exercise phase only V[O.sub.2] results were also similar with values of 30.4% during constant exercise and 30.3% during interval exercise. Considering the [O.sub.2] usage rate per liter, similar values across all phases were found again with no significant differences. Similar values of EPOC were reported in young males when comparing constant and interval protocols which supports the results found in the current research (9).

Ventilation

Ventilatory equivalent ([V.sub.E]) values in L[min.sup.-1] also showed similarly higher values for interval protocol. Ventilation is associated with metabolic demand for VC[O.sub.2] and [V.sub.E]/VC[O.sub.2] is used to assess the efficiency of [V.sub.E] (8). The values in the current study show that both constant exercise 33.6 L[min.sup.-1] and interval 32.3 L[min.sup.-1] were slightly higher than previously reported (8), but decreased during exercise (constant 33.6, and interval 32.3) which has also been reported previously (15).

Respiration Ratios

Respiratory exchange ratios and respiratory rates also provided no significant differences between the two protocols. The baseline (0.80) and exercise phase RER (1.01 interval) values are within normal resting levels and 95%CI range was less than 0.04 above or below the mean. This is in conflict with previous research, but it may be explained by the different populations used between the studies. The peak RER has been reported at 1.10 to 1.20 or higher (7) and normally indicates an end to a V[O.sub.2] max test. The RER values found in the current study match the percentages used and rated at moderate intensity. The similarity in RER between the two protocols also suggests similar use of energy sources between the two protocols and resultant similar oxygen consumption values. However, there were moderate correlations between post exercise phase RER and V[O.sub.2] submax (R = 0.523), and exercise phase [O.sub.2] usage (R = 0.514) in the interval protocol, yet no correlations between the same measures for the constant protocol. Respiration rates also showed similarities across all phases with no significant differences.

Heart Rates

Mean HRs differed by less than 1 beat x [min.sup.-1] or 1.2%, during exercise and recovery phases which was matched by the RPE values of 11.4 and 11.3 rated on the Borg scale. In younger populations, heart rates have been reported as achieving higher values for an interval protocol (9). For the constant exercise protocol the mean HR slowly increased over the course of the 20-min exercise phase, while the interval protocol had rapidly changing peaks and troughs. The rate of change from start to finish was similar for both protocols with general trend lines being almost identical. The constant protocol produced a range of 35.6 beats [min.sup.-1] between highest and lowest during the exercise phase (4 to 24 min), whilst the interval produced a range of 40.6 beats x [min.sup.-1]. If we ignore the first 2 min of each exercise phase allowing for HRs to increase under the new work levels, the range reduces to 12.1 beats x [min.sup.-1] for constant and 22.6 beats x [min.sup.-1] for interval which is now noticeably different as you would expect between the two types of exercise protocols.

As this participant group has not been previously studied, and naturally this response not reported, we can still deduct several things from this. Firstly, the difference in range during the exercise phase was quite small and helps explain the similar values in the RPE for the exercise phase. This may be accounted for by the lower percentages of V[O.sub.2] max used for the aged group of participants which is below that used by previous research with younger male participants. Further, the total amount of work performed between the two protocols was also the same and along with similar values in V[O.sub.2] and HRs, explains the similar values in the reported RPE. The correlations between post exercise phase HRs and other measures produced the greatest amount of variability with four instances where a correlation occurred with one protocol and not the other. There appears to be no real pattern of these different correlations that can be explained through the literature and may require further study. Finally, participants were also questioned about the different protocols and most stated they enjoyed the interval training protocol more and suggested it kept them interested and was easier to work with.

CONCLUSIONS

Oxygen consumption during the exercise phase of the interval protocol was 16% higher, when compared to the constant exercise protocol. The HR variation during the exercise phase increased by 12.1 beats [min.sup.-1] for the constant protocol, and when compared to the 22.6 beats [min.sup.-1] increase during the interval protocol suggests interval exercise protocol may be effective methods of improving general fitness and condition of an elderly population.

Practical Implications

1. An interval exercise protocol elicits higher V[O.sub.2] when compared to a constant exercise protocol in the aged population, and should be considered for improved physical conditioning.

2. In populations similar to those used in this study, there are no significant differences between genders when comparing constant and interval protocols and all participants can be dealt with equally.

3. The self-reported feedback suggested the interval exercise protocol was more enjoyable when compared to the constant exercise protocol and may contribute to increased adherence of exercise routines.

Address for correspondence: McKean MR. PhD, Fitness Research, School of Health and Sport Science, Faculty of Science, Health and Education, University of Sunshine Coast, Locked Mail Bag, Maroochydore DC, Queensland 4558, Australia. Telephone: +61 7 54565528, Fax: +61 54564600, Email: mmckean@usc.edu.au

REFERENCES

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(2.) Arnardottir R, Boman G, Larsson K, Hedenstrom H, Emtner M. Interval training compared with continuous training in patients with COPD. Respir Med. 2007; 101:1196-1204.

(3.) Borg G. Perceived exertion as an indicator of somatic stress. Scand J Rehabil Med. 1970; 2:92.

(4.) Daussin FN, Zoll J, Dufour SP, Ponsot E, Lonsdorfer-Wolf E, Doutreleau S, Mettauer B, Piquard F, Geny B, Richard R. Effect of interval versus continuous training on cardiorespiratory and mitochondrial functions: relationship to aerobic performance improvements in sedentary subjects. Am J Physiol-Regul, Integr Compar Physiol. 2008; 295: R264.

(5.) Francis DP, Davies LC, Willson K, Wensel R, Ponikowski P, Coats AJS, Piepoli M. Impact of periodic breathing on measurement of oxygen uptake and respiratory exchange ratio during cardiopulmonary exercise testing. Clin Sci. 2002; 103:543-552.

(6.) Helgerud J, Hoydal K, Wang E, Karlsen T, Berg P, Bjerkaas M, Simonsen T, Helgesen C, Hjorth N, Bach R. Aerobic high-intensity intervals improve V[O.sub.2] max more than moderate training. Med Sci Sports Exer. 2007; 39:665.

(7.) Ingle L, Witte KK, Cleland JGJF, Clark AL. The prognostic value of cardiopulmonary exercise testing with a peak respiratory exchange ratio of <1.0 in patients with chronic heart failure. Intern J Cardiol. 2008; 127:88-92.

(8.) Koch B, Schaper C, Ittermann T, Spielhagen T, Dorr M, Volzke H, Opitz CF, Ewert R, Glaser S. Reference values for cardiopulmonary exercise testing in healthy volunteers: the SHIP study. Eur Respir J. 2009; 33:389.

(9.) McGarvey W, Jones R, Petersen S. Excess post-exercise oxygen consumption following continuous and interval cycling exercise. Int J Sport Nutr Exer Metab. 2005; 15:28.

(10.) Morris N, Gass G, Thompson M, Conforti D. Physiological responses to intermittent and continuous exercise at the same relative intensity in older men. Euro J Appl Physiol. 2003; 90:620-6253.

(11.) Nemoto K, Gen-no H, Masuki S, Okazaki K, Nose H. Effects of high-intensity interval walking training on physical fitness and blood pressure in middle-aged and older people. Presented at Mayo Clin Proc. 2007.

(12.) Norton K, Olds T, Bowes D, Van Ly S, Gore C. Applying the Sports Medicine Australia preexercise screening procedures: who will be excluded? J Sci Med Sport. 1998; 1:38-51.

(13.) Paganini-Hill A, Kawas CH, Corrada MM. Activities and mortality in the elderly: The leisure world cohort study. J Gerontol Series A: Biol Sci Med Sci. 2011; 66:559.

(14.) Phibbs BP, Buckels LJ. Comparative yield of ECG leads in multistage stress testing. Am Heart J. 1975; 90:275.

(15.) Sullivan M, Higginbotham M, Cobb F. Increased exercise ventilation in patients with chronic heart failure: intact ventilatory control despite hemodynamic and pulmonary abnormalities.

Circulation. 1988; 77:552.

(16.) Talanian JL, Galloway SDR, Heigenhauser GJF, Bonen A, Spriet LL. Two weeks of highintensity aerobic interval training increases the capacity for fat oxidation during exercise in women. J Appl Physiol. 2007; 102:1439.

(17.) Tanaka H, Monahan KD, Seals DR. Age-predicted maximal heart rate revisited. J Am Coll Cardiol. 2001; 37:153.

(18.) Thompson WR, Gordon NF, Pescatello LS. ACSM's Guidelines for Exercise Testing and Prescription. Wolters Kluwer: Lippincott Williams & Wilkins, 2010.

(19.) Vogiatzis I, Nanas S, Roussos C. Interval training as an alternative modality to continuous exercise in patients with COPD. Eur Respir J. 2002; 20:12.

(20.) Wisloff U, Stoylen A, Loennechen JP, Bruvold M, Rognmo O, Haram PM, Tjonna AE, Helgerud J, Slordahl SA, Lee SJ. Superior cardiovascular effect of aerobic interval training versus moderate continuous training in heart failure patients: a randomized study. Circulation. 2007; 115:3086.

Timothy B. Stockwell, Mark R. McKean, and Brendan J. Burkett

Fitness Research, School of Health and Sport Sciences, Faculty of Science, Health and Education, University of Sunshine Coast, Queensland, Australia
Table 1. Constant and Interval protocol results for V[O.sub.2],
V[O.sub.2]-kg, VC[O.sub.2], [V.sub.E], [V.sub.E]-V[O.sub.2], and
[V.sub.E]-VC[O.sub.2] presented as mean (95% CI) with differences
(Interval-Constant) presented as absolute (raw units) and effect
statistic percentage (95% CI).

                                      Constant (50%)
Volume of [O.sub.2] STPD
(V[O.sub.2]--Lx[min.sup.-1])
Warm-Up (2 min)                    0.424 (0.353,0.495)
Exercise (20 min)                  1.076 (0.866,1.286)
Cool-Down (2 min)                  0.804 (0.655,0.952)
Post-Exercise (20 min)             0.247 (0.199,0.295)
Volume [O.sub.2] STPD
(V[O.sub.2]--mLx
  [kg.sup.-1]x[min.sup.-1])
Warm-Up                            5.4 (4.6,6.2)
Exercise                          13.7 (11.1,16.3)
Cool-Down                         10.2 (8.3,12.1)
Post-Exercise                      3.1 (2.6,3.6)
Volume C[O.sub.2] STPD
(VC[O.sub.2]--Lx[min.sup.-1])
Warm-Up                            0.338 (0.277,0.399)
Exercise                           1.024 (0.818,1.230)
Cool-Down                          0.782 (0.627,0.936)
Post-Exercise                      0.299 (0.181,0.277)
Ventilatory
Equivalent BTPS
([V.sub.E]--Lx[min.sup.-1])
Warm-Up                           12.359 (10.704,14.103)
Exercise                          31.691 (25.955,37.427)
Cool-Down                         25.834 (21.358,30.311)
Post-Exercise                      8.602 (7.276,9.927)
Ventilatory
Equivalent Ratio for [O.sub.2]
([V.sub.E]/V[O.sub.2])
Warm-Up                           31.2 (28.3,34.1)
Exercise                          32.0 (26.4,37.6)
Cool-Down                         36.2 (28.5,43.9)
Post-Exercise                     37.8 (33.1,42.5)
Ventilatory
Equivalent Ratio for C[O.sub.2]
([V.sub.E]/VC[O.sub.2])
Warm-Up                           39.1 (35.3,42.9)
Exercise                          33.6 (28.0,39.3)
Cool-Down                         37.4 (28.8,46.0)
Post-Exercise                     41.3 (35.4,47.1)

                                    Interval (70%:30%)
Volume of [O.sub.2] STPD
(V[O.sub.2]--Lx[min.sup.-1])
Warm-Up (2 min)                    0.486 (0.390,0.582)
Exercise (20 min)                  1.128 (0.941,1.286)
Cool-Down (2 min)                  0.750 (0.622,0.878)
Post-Exercise (20 min)             0.267 (0.189,0.345)
Volume [O.sub.2] STPD
(V[O.sub.2]--mLx
  [kg.sup.-1]x[min.sup.-1])
Warm-Up                            6.2 (5.2,7.3)
Exercise                          14.4 (12.4,16.3)
Cool-Down                          0.7 (.06,0.9)
Post-Exercise                      3.3 (2.6,4.1)
Volume C[O.sub.2] STPD
(VC[O.sub.2]--Lx[min.sup.-1])
Warm-Up                            0.393 (.0312,0.473)
Exercise                           1.105 (0.916,1.294)
Cool-Down                          0.746 (0.616,0.876)
Post-Exercise                      0.247 (0.169,0.325)
Ventilatory
Equivalent BTPS
([V.sub.E]--Lx[min.sup.-1])
Warm-Up                           14.013 (11.815,16.211)
Exercise                          34.887 (29.670,40.104)
Cool-Down                         25.659 (21.762,29.556)
Post-Exercise                      9.668 (7.014,12.323)
Ventilatory
Equivalent Ratio for [O.sub.2]
([V.sub.E]/V[O.sub.2])
Warm-Up                           30.3 (28.0,32.6)
Exercise                          31.5 (28.9,34.1)
Cool-Down                         35.4 (32.4,38.5)
Post-Exercise                     39.4 (34.5,44.2)
Ventilatory
Equivalent Ratio for C[O.sub.2]
([V.sub.E]/VC[O.sub.2])
Warm-Up                           37.5 (34.8,40.1)
Exercise                          32.3 (30.
Cool-Down                         35.6 (32.8,38.4)
Post-Exercise                     42.8 (37.6,48.0)

                                  Effect in Raw Units
Volume of [O.sub.2] STPD
(V[O.sub.2]--Lx[min.sup.-1])
Warm-Up (2 min)                    0.06 (-0.01,0.13)
Exercise (20 min)                  0.05 (-0.04,0.14)
Cool-Down (2 min)                 -0.05 (-0.14,0.09)
Post-Exercise (20 min)             0.02 (-0.03,0.07)
Volume [O.sub.2] STPD
(V[O.sub.2]--mLx
  [kg.sup.-1]x[min.sup.-1])
Warm-Up                            0.83 (-0.03,1.70)
Exercise                           0.71 (-0.67,2.09)
Cool-Down                         -0.64 (-1.90,0.63)
Post-Exercise                      0.23 (-0.41,0.86)
Volume C[O.sub.2] STPD
(VC[O.sub.2]--Lx[min.sup.-1])
Warm-Up                            0.05 (-0.01,0.11)
Exercise                           0.08 (-0.01,0.17)
Cool-Down                         -0.04 (-0.13,0.05)
Post-Exercise                      0.02 (-0.03,0.07)
Ventilatory
Equivalent BTPS
([V.sub.E]--Lx[min.sup.-1])
Warm-Up                            1.65 (-0.29,3.60)
Exercise                           3.20 (-0.09,6.49)
Cool-Down                         -0.17 (-3.15,2.80)
Post-Exercise                      1.07 (-0.079,
Ventilatory
Equivalent Ratio for [O.sub.2]
([V.sub.E]/V[O.sub.2])
Warm-Up                           -0.89 (-2.55,0.76)
Exercise                          -0.52 (-4.15,3.11)
Cool-Down                         -0.77 (-6.12,4.59)
Post-Exercise                      1.60 (-2.05,5.24)
Ventilatory
Equivalent Ratio for C[O.sub.2]
([V.sub.E]/VC[O.sub.2])
Warm-Up                           -1.64 (-3.78,0.50)
Exercise                          -1.38 (-5.43,2.66)
Cool-Down                         -1.85 (-8.31,4.61)
Post-Exercise                      1.53 (-2.53,5.59)

                                       Effect (%)
Volume of [O.sub.2] STPD
(V[O.sub.2]--Lx[min.sup.-1])
Warm-Up (2 min)                   16.6 (-3.8,41.3)
Exercise (20 min)                 15.7 (-13.1,54.1)
Cool-Down (2 min)                  5.1 (-26.1,49.4)
Post-Exercise (20 min)             1.7 (-15.9,23.0)
Volume [O.sub.2] STPD
(V[O.sub.2]--mLx
  [kg.sup.-1]x[min.sup.-1])
Warm-Up                           16.6 (-3.8,41.3)
Exercise                          15.7 (-13.1,54.1)
Cool-Down                          5.1 (-26.1,49.4)
Post-Exercise                      1.7 (-15.9,23.0)
Volume C[O.sub.2] STPD
(VC[O.sub.2]--Lx[min.sup.-1])
Warm-Up                           17.7 (-3.5,43.7)
Exercise                          18.7 (-11.8,59.7)
Cool-Down                          7.7 (-25.0,54.6)
Post-Exercise                      1.2 (-16.9,23.1)
Ventilatory
Equivalent BTPS
([V.sub.E]--Lx[min.sup.-1])
Warm-Up                           13.4 (-4.0,34.0)
Exercise                          17.0 (-7.3,47.6)
Cool-Down                          6.5 (-18.8,39.8)
Post-Exercise                      4.4 (-12.2,24.1)
Ventilatory
Equivalent Ratio for [O.sub.2]
([V.sub.E]/V[O.sub.2])
Warm-Up                           -2.5 (-7.0,2.2)
Exercise                           0.6 (-6.1,7.8)
Cool-Down                          1.1 (-7.2,10.1)
Post-Exercise                      4.3 (-2.4,11.6)
Ventilatory
Equivalent Ratio for C[O.sub.2]
([V.sub.E]/VC[O.sub.2])
Warm-Up                           -3.7 (-8.0,0.08)
Exercise                          -1.8 (-8.9,5.8)
Cool-Down                         -1.1 (-10.1,8.9)
Post-Exercise                      4.5 (-2.8,12.3)

Table 2. Constant and interval protocol results for RER, RR,
Fe[O.sub.2], FeC[O.sub.2], HR, presented as mean (95% CI) with
differences (Interval-Constant) presented as absolute (raw units) and
effect statistic percentage (95% CI).

                            Constant (50%)        Interval (70%:30%)

Respiratory Exchange Ratio
Warm-Up (2 min)             0.80 (0.77,0.83)      0.81 (0.78,0.84)
Exercise (20 min)           0.95 (0.93,0.98)      0.98 (0.95,1.00)
Cool-Down (2 min)           0.98 (0.95,1.00)      1.00 (0.97,1.03)
Post-Exercise (20 min)      0.93 (0.90,0.96)      0.92 (0.90,0.95)

Respiratory rate
  (breathsx[min.sup.-1])
Warm-Up                     16.6 (14.3,18.9)      17.2 (15.1,19.3)
Exercise                    24.1 (21.6,26.5)      24.6 (22.5,26.7)
Cool-Down                   23.7 (21.0,26.3)      23.3 (20.9,25.6)
Post-Exercise               16.9 (14.1,19.3)      16.5 (13.8,19.2)

Fractional Expired
  [O.sub.2] (%)
Warm-Up                     17.1 (16.8,17.4)      17.0 (16.81,17.3)
Exercise                    17.0 (16.6,17.4)      17.0 (16.8,17.3)
Cool-Down                   17.4 (17.0,17.7)      17.5 (17.2,17.7)
Post-Exercise               17.6 (17.4,17.9)      17.8 (17.5,18.0)

Fractional Expired
  C[O.sub.2] (%)
Warm-Up                     3.2 (3.0,3.5)         3.3 (3.1,3.5)
Exercise                    3.8 (3.5,4.1)         3.8 (3.6,4.0)
Cool-Down                   3.5 (3.1,3.9)         3.5 (3.2,3.7)
Post-Exercise               3.1 (2.8,3.4)         3.0 (2.8,3.2)

Heart Rate
  (beats x [min.sup.-1])
Warm-Up                     75.7 (69.0,82.5)      76.3 (70.4,82.3)
Exercise                    104.7 (100.3,109.1)   105.4 (100.0,110.8)
Cool-Down                   100.1 (95.7,104.6)    97.1 (90.4,103.7)
Post-Exercise               78.2 (692,87.1)       75.4 (68.2,82.6)

                            Effect in Raw Units   Effect (%)

Respiratory Exchange Ratio
Warm-Up (2 min)             0.01 (-0.02,0.04)     1.2 (-2.4,4.9)
Exercise (20 min)           0.02 (0.01,0.04)      2.5 (0.08,4.3)
Cool-Down (2 min)           0.02 (0.00,0.05)      2.2 (-0.04,4.8)
Post-Exercise (20 min)      0.00 (-0.02,0.02)     -0.2 (-2.5,2.2)

Respiratory rate
  (breathsx[min.sup.-1])
Warm-Up                     0.57 (-0.31,1.46)     3.7 (-1.4,9.1)
Exercise                    0.51 (-0.32,1.34)     2.6 (-0.7,6.0)
Cool-Down                   -0.43 (-2.15,1.28)    -1.5 (-9.1,6.6)
Post-Exercise               -0.41 (-2.13,1.31)    -3.4 (-15.1,9.9)

Fractional Expired
  [O.sub.2] (%)
Warm-Up                     -0.10 (-0.25,0.05)    -0.6 (-1.4,0.3)
Exercise                    0.05 (-0.11,0.22)     0.3 (-0.6,1.3)
Cool-Down                   0.08 (-0.12,0.27)     0.5 (-0.6,1.5)
Post-Exercise               0.13 (-0.04,0.29)     0.7 (-0.2,1.6)

Fractional Expired
  C[O.sub.2] (%)
Warm-Up                     0.11 (-0.01,0.23)     3.8 (-0.7,8.5)
Exercise                    0.02 (-0.15,0.20)     1.9 (-5.1,9.3)
Cool-Down                   -0.03 (-0.22,0.17)    1.2 (-7.9,11.2)
Post-Exercise               -0.14 (-0.30,0.03)    -3.7 (-9.7,2.8)

Heart Rate
  (beats x [min.sup.-1])
Warm-Up                     0.60 (-4.15,5.35)     1.1 (-4.2,6.5)
Exercise                    0.71 (-1.58,3.01)     0.5 (-1.8,2.9)
Cool-Down                   -3.07 (-7.05,0.91)    -3.6 (-7.8,0.9)
Post-Exercise               -2.77 (-7.06,1.52)    -3.2 (-8.1,2.0)

Table 3--Correlations reported only for measures where r >.400**

                     V[O.sub.2]kg   VeV[O.sub.2]   VC[O.sub.2]

V[O.sub.2]           .950 **        -.529 **       .993 **
V[O.sub.2]kg                        -.503 **       .943 **
[V.sub.E]V                                         -.488 **
  [O.sub.2]
VC[O.sub.2]
[V.sub.E]
RER
RR
[F.sub.E][O.sub.2]
[F.sub.E]C[O.sub.2]

                     [V.sub.E]   RER        RR

V[O.sub.2]           977 **      .490 **    .528 **
V[O.sub.2]kg         .944 **     .473 **    .622 **
[V.sub.E]V           -.439 **
  [O.sub.2]
VC[O.sub.2]          .987 **     .553 **    .530 **
[V.sub.E]                        .557 **    .587 **
RER
RR
[F.sub.E][O.sub.2]
[F.sub.E]C[O.sub.2]

                     Fe[O.sub.2]   FeC[O.sub.2]   HR

V[O.sub.2]           -.630 **      .751 **        .573 **
V[O.sub.2]kg         -.594 **      .708 **        .646 **
[V.sub.E]V           .825 **       -.767 **
  [O.sub.2]
VC[O.sub.2]          -.581 **      .736 **        .587 **
[V.sub.E]            -.506 **      .670 **        .592 **
RER                                .554 **        .483 **
RR                                                .502 **
[F.sub.E][O.sub.2]                 -.933 **
[F.sub.E]C[O.sub.2]                               .511 **

**Correlation is significant at the 0.01 level (2-tailed)
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Author:Stockwell, Timothy B.; McKean, Mark R.; Burkett, Brendan J.
Publication:Journal of Exercise Physiology Online
Article Type:Report
Date:Apr 1, 2012
Words:5501
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