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December 2014

Determining Your Power Grip Size

Allan Brown 2014 Posted by Allan Brown, PT

Hands come in different sizes and shapes.  When choosing a tool for the job picking a tool that fits your hand makes the work more efficient.  A handle too large or too small will cause early fatigue because of over or under gripping.  How do you decide what is the right size tool for you? 

The first step is to determine the size of your hand.  According to: Champney 1979: Muller Borer1981: NASA 1978; The 50th percentile hand length for male is 7.5”, female 7.2”.  Grip diameter 1.9” male, 1.7” female

To measure your hand size measure the distance from your wrist crease to the tip of your middle finger with the palm open. (see image below)   You will use this figure to determine your grip sizeHand 2

Take 20% of your hand size to determine your grip diameter.  For example if your hand size is 7.5” multiply it by .20 for your grip size. (7.5”X.20=1.5”) so your grip diameter is 1.5”.

HandYou can check this number by making a circle with your index and thumb and measuring the distance across the circle.  It should be close to the figure you calculated for your grip diameter.

Once you know your grip diameter you can calculate your grip size.  Simply multiply your grip diameter by 3.14 (aka Pi) for your grip size.  In the example above grip diameter 1.5”X3.14=4.7”grip size

Once you know your grip diameter and grip size you can select tools that fit your hand and will be more efficient to use.  For a power grip like hammering NIOSH recommends tool handle diameters between 1.25” – 2”.  Use your grip diameter and find the tool handle closest to your size.  Handles can be built up with tape or foam padding to increase their diameter.

See NIOSH’s link below for a booklet on how to select non-powered hand tools.

Santa's Workshop Reins In On Injuries

Greg LaRochelle 2014 Posted by Greg LaRochelle

It wasn’t always safety first at Santa’s workshop when the elves labored feverishly to finish all the toys needed for the big night.  There was the time Dingle chipped a front tooth when he lost hold of the small wood chisel he was sharpening on the bench grinder.  With no face shield available and the tool rest and tongue guard not adjusted properly, the chisel became a projectile and glanced off his mouth.  Fortunately, Herbie came to his aid and applied a tooth crown.  And then there was the group of tall elves that constantly complained of neck and upper back pain from stooping over the low workbenches.  Finger cuts were commonplace and combustible wood dust accumulated to near dangerous levels for the lack of an adequate dust collection system.

This all changed as the big guy, stressed to the point of losing weight and tired of the missus nagging him to “Eat, Papa, eat!” finally put his foot down and called a meeting to order.  “We need to take action!” he exclaimed, asking for input on ideas to improve workplace safety.  One of the elves piped up having caught wind of the news that MEMIC offers an abundance of online safety resources to its policyholders. 

Soon after contacting his agent and signing up, a wonderful turn of events happened making Santa the jolly fellow that we’ve come to know.  A safety committee was started after viewing the Safety Committee Webinar in the Webinars on Demand section of the MEMIC Safety Director.  Workbench heights were adjusted after taking advantage of the E-Ergo Request tool.  Weekly safety toy box talks were initiated using the Safety Net blog articles to educate the elves on a wide array of safety topics.  Personal protective equipment including cut resistant gloves was provided upon using the PPE Hazard Evaluation Form available in the resource library.  And of course, the use of a shaky stepladder to top the tree with a shiny star was abandoned when Bumble joined the team.

MEMIC encourages all of its policyholders to take full advantage of its online resources including the Safety Director, Video Lending Library, Safety Net Blog, and Workshops & Webinars to foster a safer workplace.  To get started, go to MEMIC's website.

Not All Mice Are Created Equal

Maureen-Anderson Posted by: Maureen Graves-Anderson

As an ergonomist, one of the most common complaints centers on the computer mouse. This necessary evil of computer input is the bane of so many workers, across all industries, men and women, young and old. It all boils down to one question: “Which mouse should I use?” Unfortunately, there is no one answer. Like everything else in ergonomics, there is no one-size-fits-all. Here are some hints to help you decide the best option for you.

  1. Hand position – a more neutral hand position (palm on side) is generally more comfortable than the typical prone position (palm down). Studies have shown the neutral position uses less muscle activity.
  2. Size – a size closer matched to your hand size also results in less muscle activity. Beware the tiny portable mouse; a 2008 study found it had a high rate of awkward positions of the hand and high muscle activity. Those tiny mice should only be used for short durations.
  3. Connectivity – many struggle with cords that are too short or heavy. Cordless mice are better but bring along problems with managing batteries that seem to need frequent changes. Those batteries always seem to die when you are in the middle of an important task. If you are using a corded mouse, ensure the cable is long enough so you can use the mouse in the proper location. 
  4. Task – you need to consider what you are doing with your computer mouse. Are you doing precise motions such as CAD or art work? Are you browsing the internet? Different tasks may lead you to a different mouse selection. Technology magazines and websites often cover the latest and greatest computer input devices.

Now that you have your perfect mouse, don’t forget that your behavior is the biggest factor in reducing risks from using the computer mouse. The best equipment does no good if you don’t use it properly or follow ergonomic guidelines. Here are some tips:

  1. Grip – the mouse should fit comfortably in your hand, and should take minimal gripping force to operate. Don’t clutch that mouse in a death grip or awkward claw grip.
  2. Duration – take frequent micro-breaks and change work tasks so that you give your hands a break. If you are under pressure to complete tasks, we know that the muscular activity associated with the mouse increases. One study showed a 140% increase in wrist forces when faced with mental and precision stressors!
  3. Location – make sure that new mouse is located properly. It should be directly in front of your body. Your arm should not be rotated outwards to use the mouse. The mouse should be on the same plane as the keyboard. If you use a keyboard tray, ensure that the tray can fit your mouse and provide a stable platform for use.
  4. Seek alternatives – can you accomplish your task with less mouse use? Can you use keyboard short cuts? Can you use the mouse with the opposite hand?

In summary, you and your co-workers are unique and one computer mouse cannot satisfy all. Consider my suggestions when you select your next computer mouse. You can also check out the ergonomic resources available online within the MEMIC Safety Director.


Best Mice of 2014, PC Magazine, Feb 13, 2014

Hengel et al, Smaller external notebook mice have different effects on posture and muscle activity, Clinical Biomechanics, July 2008

Visser et al, Effects of precision demands and mental pressure on muscle activation and hand forces in computer mouse tasks, Ergonomics, Vol. 47, Issue 2, 2004

Fatalities In The Workplace

John DeRoia 2014 Posted by John DeRoia

According to the Bureau of Labor and Statistics (BLS), there were 4,405 workplace fatalities in 2013.  That equates out to almost 85 deaths per week or more than 12 per day!  This is a very somber number.  Although this is a staggering statistic, BLS reports that this is the lowest number of fatalities in a year since they started collecting data in 1992.  Prior to OSHA’s inception in 1970, there were a startling 38 workplace deaths a day. 

Federal OSHA, with their state partners, is a relatively small group.  They only number around 2,200 inspectors.  These 2,200 inspectors are, in part, responsible for the safety and well being of 130 million workers employed at more than 8 million worksites around the country.  That translates to approximately 1 compliance officer for every 59,000 workers.

In a related issue, remember that OSHA has changed the reporting requirements regarding fatalities, hospitalizations, and amputations.  These changes are summarized on the OSHA website

With the few OSHA Compliance Officers, it is clear that they cannot be responsible for every employer’s safety program.  Safety needs to be a top priority at each work location starting from top management and all the way down to the newest employee.  Although OSHA’s role is to assist employers in the prevention of workplace injuries, it is not possible for them to be present with any frequency.  Each employer has to take responsibility for workplace safety in order to reduce the likelihood of any injury or fatality.  For more information on workplace accident/injury trends please visit the Bureau of Labor Statistics or the OSHA website. Additionally, in the coming months MEMIC will be conducting a webinar entitled Fatalities in the Work Place.  Be on the look out for registration information for this webinar or check out the other safety resources available from the MEMIC website.     


Source: U.S. Bureau of Labor Statistics, U.S. Department of Labor, 2014.