Ergonomic Analysis of Power “Cots” Shows the iNX Eliminates Lifting During Patient Handling


EMS is a high risk business for individuals and agencies alike. EMS providers experience high rates of musculoskeletal injury, most commonly sprains, strains, or back injuries. A typical injury costs over $20,000 in direct expenses and results in an average 90 days of lost work time. Independent research has proven that operators using the iN∫X™ Integrated Patient Handling & Loading System™ do not have to support the weight of the cot and patient during loading and unloading, effectively reducing and eliminating these risks.

Power Cots Reduce Injury

Research has shown the most common cause of lifting oriented injuries, like what we see in EMS, is cumulative trauma; repetitive loading of the joints and spine which leads to tissue fatigue and eventual tissue failure.1 Preventing injury requires greatly reducing or eliminating repetitive loading forces. EMS specific research has shown that power cots reduce compression forces on the body when raising and lowering a patient,5 while other research has shown that implementing power cots across an agency reduces occupational injury rates and incidents from raising and lowering.3 This research also demonstrates reduced injury rates corresponding to lower workers compensation claims and lost work days.4


While power cots reduce injury from raising and lowering, providers are still exposed to injury risks while loading and unloading a cot. Understanding this, FERNO recognized the need to create a device that would eliminate loading forces across the patient handling cycle while both raising and lowering, and loading and unloading. The iN∫X Integrated Patient Handling & Loading System was created to meet this need.

The Experiment

To confirm the reduction in loading and unloading forces, independent ergonomic experts studied EMTs and paramedics loading and unloading variable patient weights (100/150/200lbs) from a simulated ambulance deck while comparing two different types of power ambulance cots: The FERNO iN∫X and the Stryker® Power-PRO®. Researchers tested the effect of cot and weight conditions on average and peak muscle activity (arm, shoulders, and back) measured by Maximum Voluntary Exertion (MVE) normalized across all test subjects. Researchers also tested peak and static loads imposed on the subject while handling the cot, and subjects’ rating of perceived exertion.2

Experimental Results

Data collected showed the iN∫X consistently elicited lower muscle activity than the Power-PRO. For all three patient weights tested, muscle activity did not increase as weight on the iN∫X increased, while muscle activity increased as weight on the Power-PRO increased. Average and peak muscle activity averaged less than 10% MVE for the iN∫X at all weights tested, while muscle activity for the Power-PRO was 2-12 times greater for each muscle group, with peak activity as high as 40% of MVE.2

Force plate data clearly showed the subjects did not support the weight of the loaded iN∫X while the legs were extending or retracting during tasks across all weight conditions. When using the Power-PRO subjects held an average of 126 lbs across the three weight conditions while performing the same tasks. For each additional 50 lbs of patient weight on the Power-PRO, subjects experienced a 17 lb increase in external load, with an average of 180 lbs peak force when handling a 200 lb patient load.2

Test subjects’ ratings of perceived exertion (RPE) were lower for the iN∫X than the Power-PRO, including lower ratings for the iN∫X loaded with the greatest test weight when compared to ratings for the Power-PRO loaded with the lowest test weight.


The iN∫X design has a direct impact on the external loads operators experience, internal muscle activation required to counteract those loads, and subjective perceptions of exertion. Operators do not have to support the weight of the cot and patient during loading and unloading and the iN∫X effectively nullifies the effects from increases in patient weight 2.

1. MCGILL, S.M., 1997, The Biomechanics of Low Back Injury: Implications on Current Practice in Industry and the Clinic. Biomechanics, 30, 465-474.
2. SOMMERICH, C.M., LAVENDER, S.A., 2013, A biomechanical and subjective assessment and comparison of two powered ambulance cots. Final Report; Department of Integrated Systems Engineering, The Ohio State University
3. STUDNEK, J.R., CRAWFORD, J. and FERNANDEZ, A.R., 2012, Evaluation of Occupational Injuries in an Urban Emergency Medical Services System Before and After Implementation of Electrically Powered Stretchers. Applied Ergonomics, 43, 198-202.
4. FREDERICKS, T.K., BUTT, S.E. and HOVENKAMP, A., 2009, The impact of gurney design on EMS personnel. Proceedings of XXIst Annual International Occupational Ergonomics and Safety Conference, Dallas, TX: International Society of Occupational Ergonomics and Safety, 112-117.
5. FREDERICKS, T.K., BUTT, S.E., HARMS, K.S., and BURNS, J.D., 2013 Evaluation of Medical Cot Design Considering the Biomechanical Impact on Emergency Response Personnel. The XXVth Annual Occupational Ergonomics and Safety Conference, June 6-7, 2013

Up to 300% More Loading Flexibility with POWER X1


Powered cots have been shown to reduce spinal compression forces in emergency service professionals by as much as 50%1. However, the EMS work environment often results in cot loading and unloading scenarios plagued by off-axis, uneven approach conditions. This, coupled with patient weight, can make the job of the EMS professional very difficult even with a powered cot, and it can result in poor ergonomics and high lumbar and joint stresses.1 At some angles, the cot may not be able to load into the fastener at all. The purpose of this study was to evaluate the angles at which two commercially available emergency cots would no longer load into the fastener.


Two emergency cots were loaded and unloaded into a simulated ambulance in this study. The FERNO POWER X1 Ambulance Cot (Wilmington, OH) and Stryker Power-PRO™ XT (Portage, MI) cot were kept on the horizontal, and one corner of a simulated ambulance was positioned at a maximum height per the ambulance floor height standard.2 Six ambulance floor orientations were tested (Figure 1). When viewed from the rear as if loading or unloading a cot, the ambulance floor was adjusted either a) parallel to the horizontal, b) at negative (-) degree increments when viewed from left to right, or c) at positive (+) degree increments from left to right. When viewed from the side, the floor was also adjusted either d) at negative (-) degree increments when viewed from rear to front, or e) at positive (+) degree increments from rear to front. When both the cot and the floor were placed on the horizontal, multiple cot approach angles were also tested (Figure 1f). The PRO F1™ Universal Cot Fastener (FERNO) and Stryker Power-LOAD® fastener were mounted to the ambulance floor per the manufacturer’s installation instructions. Each cot was loaded into the respective fastener with 1) no simulated patient and 2) a simulated patient weight of 250 lbf (1112 N). Each cot was also tested with a simulated patient weight of 700 lbf (3114 N) in scenario (f).


Both cots unloaded and loaded when the cot and fastener were parallel to the horizontal (orientation a) at both simulated patient weights. In the (b) orientation, the maximum angle the Power-PRO XT could be unloaded or loaded was -6.0 degrees at both simulated patient weights. The POWER X1 unloaded and loaded up to -12.0 degrees without weight and up to -10.7 degrees with weight, representing up to a 100% increase in flexibility. In the (c) orientation, the maximum angle at which the Power-PRO XT and POWER X1 cots could be unloaded or loaded was 3.0 degrees at both simulated patient weights. It should be noted that the (c) orientation resulted in the right side of the simulated ambulance floor being above the maximum height standard (see Figure 1c).2 In the (d) orientation, the maximum angle the Power-PRO XT could be unloaded or loaded was -3.0 degrees at both simulated patient weights. The POWER X1 unloaded and loaded up to -7.0 degrees at both simulated weights, representing a 133% increase in flexibility. In the (e) orientation, the maximum angle the Power-PRO XT could be unloaded or loaded was 3.0 degrees at both simulated patient weights. The POWER X1 unloaded and loaded up to 12.0 degrees at both simulated weights, representing a 300% increase in flexibility. The maximum approach angle capability of the Power-PRO XT cot and Power-LOAD fastener was found to be load dependent (p < 0.05) and ranged from 16 degrees at full capacity to 20 degrees with an unloaded cot. In this scenario, the Stryker Power-PRO XT would not load into the Power-LOAD without lift assistance. The POWER X1 and PRO F1 were capable of 55 degrees of off-axis approach angle regardless of the load on the patient surface (Figure 2).


If an emergency cot and ambulance floor are at different angles with respect to one another, such as is often the case when parked on a hill, driveway, or curb, or when the EMS professional approaches the back of the ambulance at a slightly off-axis angle, then the unloading and loading dynamics of the cot are changed. In some cases, the cot will not load at all even with assistance from the EMS professional. In this study, an increase in flexibility during loading and unloading was observed with the POWER X1 Ambulance Cot and PRO F1 Universal Cot Fastener as compared to the Stryker PowerPRO XT and Power-LOAD fastener combination. There was also a nearly three-fold increase in the off-axis loading capability with the POWER X1 versus the Power-PRO XT cot. At offset approach angles, cot choice can leave the EMS professional with an increase in load to bear. A cot with greater flexibility with regard to off-axis mismatch of the cot/fastener interface proved beneficial to the EMS professional in this study.

Key Definitions 

“N”=“Newton”— the standard unit of force in the International System of Units.
LBF— The pound-force (symbol: lbf, or lbf ) is a unit of force.
For purposes of this white paper, LBF represents “simulated patient weight” and “N” is used as a unit of measurement during stability testing.

(1) Fredericks et. al. Evaluation of Medical Cot Design Considering the Biomechanical Impact on Emergency Response Personnel, 2013. (2) Federal Specification for the Star-of-Life Ambulance, KKK-A-1822.