Product Assembly
Products (ellipse by NordicTrack, HEALTHRIDER ELLIPTICAL CROSSTRAINER by ICON Health and Fitness, Inc., POWER.TRAINTM by Guthy-Renker®, and CYCLONE CROSSTRAINERTM by Quantum Television) were assembled following directions provided by the manufacturer of each product. One person assembled each product. Much variation in quality and quantity of information was noted with the assembly descriptions. Times for assembly were as follows: POWER.TRAINTM (POW)—30 minutes, CYCLONE CROSSTRAINERTM (CYC)—75 minutes, ellipse (ELL)—90 minutes, HEALTHRIDER ELLIPTICAL CROSSTRAINER (HEA)—150 minutes.

Initial Product Testing
Once assembled, products were tested to make sure all mechanisms were working. The CYC resistance control was inoperative. The resistance knob could be turned (continuously, and in both directions) without any change in resistance. However, it was determined that this would not affect the testing as the established resistance setting was adequate for the majority of the subjects and if any subjects desired a more challenging workout, they simply performed the elliptical motion faster.

Subject Selection and Familiarization
Volunteers were recruited from exercise science classes at the University (See Table 1 for subject descriptives). Human research review board procedures were followed with each subject reading and signing a human subject informed consent form and filling out a health history form.
Table 1. Descriptives of Subjects

Parameter Subjects
7 M & 7 F
Age (yr) 22.9 ± 2.6
Wt (kg) 67.8 ± 9.6
Ht (cm) 171.4 ± 7.4

Prior to testing, all subjects were thoroughly familiarized with the operation of each piece of equipment. Subjects were also shown how to increase the elliptical speed motion as another means of adjusting the workout intensity.

Randomized Study with Men and Women
Methods and Procedures
We studied the oxygen consumption (VO2), heart rate (HR), ventilation (VE), respiratory exchange ratio (RER), and ratings of perceived exertion (RPE) (Borg, 1982) to randomized 5-minute exercise trials on each device. Descriptive data was collected on stride speed and Kilocalorie (KCAL) expenditure on each product.

Following product/exercise familiarization, all subjects completed a 3-minute, non-resistive, warm-up on a cycle ergometer at 60 revolutions/min. Subjects then rested in a chair for 5 minutes to determine a baseline recovery HR. Prior to each product trial, subjects quietly rested 5 minutes and achieved a recovery HR within 10 beats/min of the established baseline before starting the next trial. This study control was established in an attempt to begin each product trial with similar physiological parameters.

Each subject self-selected the elliptical device resistance, speed and workout intensity. Directions were very clear to each subject: "Workout at a comfortable but challenging intensity similar to what you would do in a normal 30 minute workout." These directions were given to the subject before and at least once within the first minute of each exercise trial. The self-selected workout intensity was chosen to be able to generalize to actual consumer usage.

VO2, VE, RER, and KCAL were measured continuously by expired gas analysis indirect calorimetry (SensorMedics Vmax Series 29). HR was monitored continuously by telemetry (PolarTM Favor). RPE was taken at the end of each elliptical device trial.

Statistics
All data was initially analyzed using a one-factor multivariate analysis of variance (MANOVA) with repeated measures. Probability was set at p&Mac178; 0.05.
Descriptive data was analyzed using a one-way analysis of variance (ANOVA).

Results
MANOVA indicated an overall non-significant (Wilks' Lambda = 1.141, p = 0.33) within group effect. Since no significant differences were seen with the dependent variables, no further statistical analysis were warranted. Means of each dependent variable are presented in Table 2. Graphs of VO2, HR, KCAL and RPE are presented in Figure 1.


Table 2. Physiological and Psychological results of Elliptical Product Study

PARAMETER HEA CYC POW ELL
VO2 (ml/kg/min) 24.2±4.5 24.6±2.9 25.9±2.8 25.3±3.6
VE (l/min) 32.1±5.8 31.9±4.8 34.3±6.9 32.2±6.2
HR (b/min) 139.3±23.6 140.2±18.6 144.5±21.0 143.2±19.7
%HRmax 71% 71% 73% 73%
RER .85±.04 .85±.05 .85±.05 .84±.04
KCAL (min) 7.8±1.0 7.9±1.1 8.7±1.3 8.3±.8
RPE 13.0±1.7 12.8±1.4 12.7±2.2 12.5±1.9
means±standard deviation

VO2, VE, HR, KCAL, RPE, STRIDES
No significant difference was observed with oxygen consumption, ventilation, heart rate, energy expenditure and ratings of perceived exertion to the four elliptical products. This was anticipated since all four products do the same relative action and all subjects were directed to complete a similar workout on each product. Using the mean age (yr), age-predicted maximum heart rate was calculated (220 - 22.9 = 197.1), and percent of estimated maximum heart rates determined for each product (HEA = 71%, CYC = 71%, POW = 73%, ELL = 73%). Subjects met American College of Sports Medicine Guidelines (ACSM 1995; HR between 60% and 90% of heart rate max) for the improvement of cardiorespiratory endurance on each product. For the improvement of aerobic fitness with a healthy female and male population, the use of the elliptical devices tested in this study could be recommended.

Comparison of elliptical product KCAL expenditure of the men and women in this investigation (7.8 - 8.7 KCAL/min), matched by body weight (67.8 ± 9.6 kg) to the energy expenditure reported in other investigations (McArdle, Katch, & Katch, 1996), was greater than cycling at 9.4 mph (6.8 KCAl/min), playing tennis (7.4 KCAl/min), and walking (5.4 KCAl/min), but similar to intense aerobic dancing (9.2 KCAL/min), slow crawl swimming stroke (8.7 KCAl/min), moderate intensity skiing (8.1 KCAl/min), and running an 11.5 min/mile pace (9.2 KCAl/min, but less than that of running a 9 min/mile pace (13.1 KCAl/min). Thus, claims made in the various infomercials as to the efficacy of elliptical exercise compared to other modalities warrant further explanation and investigation.

The subjects ratings perceived exertion (RPE) ranged from 12.5 - 13.0 on the different products, demonstrating exertions levels in the ‘Somewhat Hard’ level. This substantiates that subjects completed a comfortable, but challenging workout on each apparatus.

During minutes 2 and 3 striding tempo for each subject was determined for each product trial. This was done by matching the striding tempo to a metronome. Subjects strided significantly faster on the HEA (111 stides/min) as compared to the CYC (104 stides/min), POW (105 stides/min) and ELL (104 stides/min). However, this did not have any affect on any physiological or psychological measures observed.

Special Notes:
Five of the seven women hit the center control guard panel on the cyclone with their knees. This is most likely attributable to the ‘Q’ angle at the knee. However, since this machine is heavily marketed to the female population, this is a consequential design flaw to this machine.

After the 6th trial, roughly over one hour of total use, the HEALTHRIDER began making a very loud metallic sound in the pivot mechanism of the device. The manufacturer was contacted and we are awaiting service at this time.

Summary
The purpose of this study was to determine the physiological effects of consumer elliptical devices. Fourteen males and females (age = 22.9 ± 3.6 yrs; wt = 67.8 ± 9.6 kg) completed randomized 5-minute trials on each product at a self-selected comfortable, but challenging intensity. Subjects were familiarized with the elliptical training following directions provided by each manufacturer. Oxygen consumption, ventilation, heart rate, respiratory exchange ratio, and ratings of perceived exertion were measured and analyzed. A one-factor MANOVA with repeated measures revealed no overall within group effect. Data indicate that elliptical training meets ACSM guidelines for the development and maintenance of cardiorespiratory improvement. All subjects enjoyed elliptical training, especially the minimal impact of the activity. Subject rating of the equipment in order of preference was ellipse, HEALTHRIDER, POWER TRAIN, and CYCLONE, respectively. It was noted that five of the seven female subjects hit the center panel on the CYCLONE with their knees. Also, after approximately one hour of usage, the HEALTHRIDER demonstrated signs of equipment failure. Service is pending at the time of this report.

References
ACSM. (1995). Guidelines for graded exercise testing and prescription (5th ed). Baltimore, MD: Lea & Fibiger.
Borg, G. A. V. (1982). Psychophysical bases of perceived exertion. Medicine and Science in Sports and Exercise, 14, 377-381.
McArdle, W. D., Katch, F. I., & Katch, V. L. (1996). Exercise Physiology: Energy, Nutrition, and Human Performance, 4th Ed. Baltimore: Williams and Wilkins