The reliability of a peak VO2 test protocol for running in the water with wet vest

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1 The reliability of a peak VO 2 test protocol for running in the water with wet vest Robert K. Stallman 1, Bjarte Vik 1, Per-Ludvik Kjendlie 1 1 Norwegian School of Sport Sciences, Oslo, Norway This study employed a T 1 -T 2 format to examine the reliability of a peak VO 2 test protocol for running in the water with the wet vest. Sixteen subjects yrs of age participated. Classic Douglas bag respirometry was used. After a 10 minute warm up (HR BPM), five 5 minute sub-maximal work loads were performed with a one minute rest interval. Thereafter, a final effort of min. to exhaustion was performed. Work load was controlled by continuous HR monitoring. Blood samples were taken for blood La analysis before and after every work effort. Pearson Product Moment correlations for T 1 to T 2 were r = 0.99, 0.97 and 0.96 for peak VO 2 (l/min), peak VO 2 (ml/kg/min) and HR (BPM), respectively. The differences between T 1 and T 2 were not significantly different at the level of confidence. Stallman, R.K., Vik, B. and Kjendlie, P.-L. (2006). The reliability of a peak VO2 test protocol for running in the water with wet vest. In: Vilas-Boas, J.P., Alves, F. and Marques, A. (Eds.), Biomechanics and Medicine in Swimming X. Portuguese Journal of Sport Sciences Vol 6, Suppl 2, Porto, pp Key words: Running in water, wet vest, peak VO 2, reliability INTRODUCTION Alternative modes of training have become increasingly popular. In some cases the alternative is an adjunct to the chosen activity. In other cases the alternative becomes a primary competitive activity itself (indoor bandy, roller-skiing, fin swimming, etc). Running in the water was launched in the 1970 s primarily for its probable therapeutic effect. In the equestrian world, horses have trained in the water since the time of the ancient Greeks and it is unlikely that they overlooked similar human activity. Submerging the body during running has several important effects not the least of which is the effect of buoyancy, reducing stress on the joints. At the same time, the stroke and minute volumes of the heart increase (9) thus an excellent potential for training effect. Many runners, during periods of injury, now run in the water to protect the injury but also to maintain the training effect. This may also reduce the time of recovery from injury (6). Some runners have exchanged part of their normal running training for running in the water, hoping to avoid injury believing the kinematics to be more specific

2 to running than e.g. cycling or swimming. Nilson and Thysell (4) however, have rejected the idea of specificity by demonstrating differences in EMG muscle activity, particularly the elimination of a support phase with its eccentric contraction, when running in deep water. Several studies have compared running in the water with running on land and treadmill running (5, 3, 6, 8, 12). Town and Bradley (11) compared running in shallow water, in deep water and on the treadmill. Generally, results show reduced maximal levels for HR and VO 2, as in swimming (1). Deep water running assisted by a flotation device is generally credited to Glen McWaters (2) who patented the wet vest in Himself, a chronically injured former distance runner, he sought activity in the water to reduce impact and joint stress. In the wake of the running in the water activity of the 80 s and 90 s, use of the wet vest or similar devices has also gained popularity in activities for persons with movement impairment special needs. Both the target group and some of the activities tend to overlap with aqua-aerobics/ aqua-gymnastics. Running in the water presents several unique problems which also must be solved. The aims of this study were a) to develop a peak VO 2 test protocol for running in deep water with the wet vest and b) to examine the reliability of that test protocol. METHODS A test-retest design was used with 1-3 days between tests. The subjects were asked to refrain from eating for the two hour period prior to testing. The tests were conducted at the same time of day and in the same location. Testing was conducted in a 25 meter pool with approximately 15 m. x 12.5 m. of deep water. The water temperature was stable at C and the air temperature stable at C. Sixteen university students served as subjects (11 male, 5 female), mean age 26 (range years). Most were participants in endurance sports including cross country, skiing, triathlon, orienteering, middle and long distance running. The test protocol was a slight modification of that used in our laboratory. It consisted of a 10 minute warm up at HR BPM followed within 2 min. by five bouts of work of 5 minutes each with one minute in between. These were at gradually increasing work- loads with the load controlled by continuous HR monitoring, with both visual and verbal feedback to the subjects. The work loads selected were at HR 120, 130, 140, 150,

3 and 160 BPM (68, 73, 79, 85, and 91% of peak HR in the water). After a rest of 2-3 minutes the subjects then performed a 3-4 minute maximum effort to exhaustion. The first minute was at a gradual increase to the maximum the subject felt could be maintained for another 2-3 minutes. The work load was controlled, as stated above, by continuous monitoring of HR. The subject wore a helmet with a Polar Sport Tester pulse watch mounted in front for visual self control. At the same time an assistant with another receiver was on the deck, close enough to receive the same signals. Any deviation from the stipulated HR by 2 BPM, was immediately communicated to the subject. Respirometry was performed by classic Douglas bag methods. Two Douglas bags were mounted on a trolley at pool side connected by a three way valve with stop watch control. The hose with a mouth piece was also connected to the helmet for stability. The first bag was opened at approximately 1 minute 30 seconds after start, with some discretion according to visual signs of fatigue in the subject. In each case, seconds elapsed before the bag was filled and the switch made to the second bag. No subject was able to continue more than 3 min.30 sec. and the one exception reached exhaustion during collection in the first bag. In this setting, gas analysis had to be performed in the laboratory. Visual monitoring of the rising O 2 uptake as in automated systems was not possible. Maximum HR values were known from previous treadmill testing. At the time the subject signaled exhaustion HR values were within 15% of the treadmill elicited maximum HR. Blood lactate values, although known only after cessation of exercise, were also in each case over 6mM. HR and lactate levels gave every reason to believe that maximum effort was attained. In any event the subjects could not have continued. Gas analysis employed the Beckman O 2 analyzer, Model 755 and the Beckman infrared CO 2 analyzer, Model 864. Blood samples were collected from the finger tip of the subject before and after warm up, in the 1 minute pause between each of the 5 increasing work loads and just before and after the 3 min 30 seconds maximum effort. An YSI, Model 23L lactate analyzer was used. Statistical analysis comprised of Pearson Product Moment correlation to examine the relationship between T 1 and T 2 and Student s t-test to examine the level of significance of differences between T 1 and T 2.

4 RESULTS The peak VO 2 values obtained were all within 15% of each subject s previous treadmill results. This conforms to numerous studies referred to in the introduction, with values for work capacity during submersion in water 10-15% lower than on land. Table 1 shows the highest and lowest values obtained as well as the mean, range and standard deviation (SD). Note that the range of values appears to be rather large. This is due to inclusion of both male and female subjects. Table 1: An overview of obtained values Parameter Highest Lowest Range SD value value Peak VO 2 (l/min) Peak VO 2 (ml/kg/min) Peak HR (BPM) Peak Lactate (mm) RQ The major thrust of this study was the T 1 T 2 reliability check. Given the anticipated practical problems and potential sources of error, the reproducibility was high. Table 2 gives an overview of the relationships between Test 1 and Test 2. Table 2: Relationship between test 1 and test 2 value (T 1 + T 2 ) SE (T 1 + T 2 ) SD (T 1 + T 2 ) range (T 1 + T 2 ) Pearson PMR t-value p- level Peak VO NS (l/min) Peak VO NS (ml/kg/min) Peak HR NS (BPM) Peak La (mm) NS DISCUSSION Maximum O 2 uptake is generally accepted as the best measure of aerobic capacity (13). Already in 1924, A.V. Hill registered a plateau or even drop in O 2 uptake as subjects continued to increase the work- load. He called this maximum O 2 uptake and suggested its relationship to aerobic capacity and endurance performance. In recognition

5 of the difficulty in establishing an absolute maximum value, the results of any given test is today usually referred to as Peak VO 2. Saltin and Åstrand (7) demonstrated that among participants in elite sport, cross country skiers attained the highest maximum VO 2 values (in ml/kg/min). They discussed specificity of training for aerobic power and the specificity of testing. While cycling e.g. gives values of approximately 10% less than running, the well trained cyclist who is not accustomed to running may obtain higher values in cycling than running. This test specificity is an argument for establishing norms in a variety of activities, particularly in relation to training prescription and monitoring of improvement over time. Test protocol must be developed and evaluated for their validity and reproducibility. Field testing of peak VO 2 presents certain practical problems. Both the nature of the activity involved and certain characteristics of the local setting present unique problems. Regarding running in the water, controlling workload intensity is necessarily less refined than in a laboratory setting. The method used in this study however, was both manageable and produced acceptable results. In a parallel study (10), the same method was used and deviation in the HR during repeated, escalating five minute work loads, was no more than 1.6 BPM throughout. The movement of subjects was of a range and velocity allowing test personnel to easily follow with Douglas bag apparatus. No problems appeared either in monitoring HR. Some care had to be taken in guiding the sample collection hose so as not to entangle the subject as he/she turned during back and forth running. The results of the reliability testing, giving correlations of 0.99, 0.97 and 0.96 for peak VO 2 (l/min), peak VO 2 (ml/kg/min) and HR respectively, were more than acceptable. Missing data made correlation analysis of the blood lactate levels values less appropriate but on the remaining data (df = 11) the r was 0.887, and the t-value was 0.11 showing no significant difference at the level of confidence despite the lower correlation. CONCLUSION It is recommended that the protocol tested in this study, with demonstrated reliability, be considered for use in peak VO 2 testing for running in the water. Modifications may be necessary because of local conditions. Running in the water can be considered a

6 useful training alternative in certain cases, given the relatively high VO 2 and HR values attained. REFERENCES 1. Holmer I, (1972). Oxygen uptake during swimming in man. J Appl Physiol 33: McWaters G, (1991). Aquatic rehabilitation. Physical Rehabilitation of Injured Athletes, W.B. Saunders & Co. pp Moen A (1994). A comparison of phys. parameters during running in the water with the wet vest and on the treadmill. MSc thesis, Nor. School of Sport Science, Oslo 4. Nilsson J, Thysell B (1990). An EMG analysis of running in the water and running on a hard surface. Swedish College of Sport Science, Stockholm 5. Risch WD, Koubenec HJ, Beckmann U, Lange S, Grauer OH (1978). The effect of graded immersion on heart volume, central venous pressure, pulmonary blood distribution and heart rate in man. Pflugers Archive 374: Ritchie SE, Hopkins WG (1991). The intensity of exercise in deep water running. International J Sports Med 12: Saltin B, Åstrand PO (1967). Maximal Oxygen Uptake in Athletes. J Appl Physiol 23: Seger J (1990). Physiological comparison of running in the water with the wet vest and running on the treadmill. MSc thesis, Swedish School of Sport Science, Stockholm. 9. Sheldahl LM, Tristani FE, Clifford PS, Hughes CV, Sobacinski KA, Morris RD (1986). Effects of head-out water immersion on response to exercise training, J Appl Physiol 60: Stallman R, Naess G, Kjendlie PL (2006) A reliability study of a lactate profile test protocol for running in the water with the wet vest, Nor. School of Sport Science, Oslo 11. Town GP, Bradley SS (1991). Maximal metabolic responses of deep and shallow water running in trained runners. Med Sci Sports Exerc. 23: Wilder RP, Brennan DK, (1993). Physiological responses to deep water running in athletes. Sports Medicine, 16: Åstrand PO, Rodahl K (1986). Textbook of Work Physiology. McGraw-Hill, N.Y.

Chapter 10 Measurement of Common Anaerobic Abilities and Cardiorespiratory Responses Related to Exercise

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