Study Design and Participants
This study was approved by the New York Institute of Technology (NYIT) Internal Review Board. Subjects were recruited via flyers posted on campus at NYIT. All participants read and signed an informed consent prior to participation in the study. All testing was conducted at the NYIT College of Osteopathic Medicine (Old Westbury, NY) Center for Sports Medicine. This study was performed in accordance with the standards of ethics outlined in the Declaration of Helsinki.
This was a randomized cross-over design experiment that enrolled 20 physically active college students who exercised at least 4 times a week. Three participants did not complete the second trial and were not used in data analysis. Seven women (age 24 ± 0.95) with a body mass index (BMI) of 23 ± 3.01 and 10 males (age 24 ± 1.8) with a BMI of 24 ± 1.8 completed the study (Fig. 1). All participants were in good self-reported health and were administered The Physical Activity Readiness Questionnaire (Par-Q) [11] screen test to assess exercise risk factors. If someone answered yes to any question they were excluded from the study. A power analysis was performed to determine the required sample size. To yield a minimum 0.80 power with an alpha level set at 0.05 would require enrolling at least 14 participants [5].
Exercise Testing
Participants performed a Bruce Protocol graded treadmill exercise test on two separate occasions. This test consists of a maximum of five 3-min stages on a treadmill [12, 13]. Participants rested supine for 15 min prior to treadmill testing. Resting physiological measures included heart rate (HR), Blood pressure (BP), Oxygen consumption (VO2) and blood lactate (BL). The criteria set for peak exercise was any of the following: (1) age-adjusted maximal heart rate attained; (2) a plateau of oxygen uptake was attained; (3) if the subject was unable to maintain the pace of the treadmill; (4) a Respiratory Exchange Ratio (RER) of over 1.3 and/or a plateau in ventilation (Ve) [11]. Additionally, the American College of Sports Medicine (ACSM) guidelines for terminating exercise testing were followed [11]. Participants were verbally encouraged to continue during exercise. All physiological measures were recorded at rest, within 1 min post- peak exercise, and at recovery minutes 4, 7, 10, and 20 post exercise.
Physiological Parameters
Testing was performed on a COSMED® CPET metabolic cart (COSMED USA Inc. Concord, CA). Heart rate was recorded using a heart rate strap that synced with the COSMED unit. Blood pressure (BP) was measured manually by an experienced clinician (exercise physiologist or physician) using an upright mercury sphygmomanometer unit (W.A. Baumanometer Co. Inc. Copiague, NY, USA). Capillary blood lactate samples were analyzed by the Accutrend® Plus Ltd portable lactate analyzer system (F. Hoffmann-La Roche, Switzerland). Outcome measures of VO2, VCO2, RER, and Ve were recorded at 1-min intervals throughout testing and recovery as measured by the COSMED unit. Outcome variables that were measured at rest, peak exercise, and recovery minutes 4, 7, 10 and 20 min included HR, VO2, BP, and BL.
All participants were randomly assigned using an online program (Research Randomizer www.randomizer.org) to perform either supine passive recovery on the first visit or supine lymphatic pump on the first visit. A minimum of 5 days was required between exercise testing days with a maximum of 10 days between testing days.
Passive Recovery
When the subject attained peak exercise according the protocol (or to the same parameters as the previous test), the treadmill was brought down from the incline and speed was reduced and all outcome measures were taken within 1 min post peak exercise. The subject was the placed in a supine position for 10 min still wearing the metabolic mask. Outcome measures were taken at minute 4, minute 7, and at the 10-min marker post peak exercise. Following 10 min of lying supine, the subject sat upright in a chair to continue to recover for another 10 min. At minute 20 following peak exercise all outcome measures were taken.
Pedal Pump Recovery
When the subject attained peak exercise according the protocol (or to the same parameters as the previous test), the treadmill was brought down from the incline and speed was reduced and all outcome measures were taken within 1 min of peak exercise. The subject was the placed in a supine position and the pedal pump technique was performed for 10 min while still wearing the metabolic mask. To standardize the intervention, the pedal pump was performed using Tekscan F-scan system (Tekscan, Inc.® South Boston, MA, USA) to measure the amount of force being applied. The average force applied was 12.8 ± 1.7 lbs. and a metronome was set to 120 cycles/minute to match parameters done in a pilot study using a whole body periodic acceleration [14, 15]. The Tekscan pads were placed on the bottom of the participants feet while the physicians applied the pumping technique (Fig. 2). Outcome measures were taken at minute 4, minute 7, and at the 10-min mark post peak exercise. Following 10 min of supine pedal pump, the subject was sat upright in a chair to continue recovery for another 10 min. At minute 20 following peak exercise all outcome measures were taken.
Data Analysis
A repeated measures ANOVA was used over time to compare all outcome measures (HR, BP, VO2, BL). Significant results from the ANOVA were further examined with a Bonferroni’s post hoc test. Statistical significance was set at p < 0.05. All data is presented as mean and standard deviation (SD).