This article is reprinted with permission from The Ergonomics Report™ Archives, where it originally appeared on March 17, 2011.
In work funded by the Office Ergonomics Research Committee (OERC), Canadian researchers Berolo, Wells and Amick performed an epidemiological study to investigate the prevalence of upper body musculoskeletal pain in mobile device users. In their introduction, they note that there are case reports and laboratory studies that suggest a link between musculoskeletal disorders (MSDs) and hand-held mobile devices, but this is the first epidemiological study, and the first to provide empirical evidence of relationships between mobile device use and symptoms of the upper extremity and neck.
Specifically, case reports have suggested a link between device use and both De Quervain's tenosynovitis and osteoarthritis at the base of the thumb (carpometacarpal joint), and laboratory studies have shown that smaller keyboards (as compared to desktop or laptop computers) may increase "static strain" on the hand and arm muscles. Lab studies have also demonstrated that user thumb postures approach their maximum range of motion while the thumb moves over the keyboard interface while, for example, texting, increasing static loading on the thumb muscles.
According to the researchers:
Our results show a consistent relationship between mobile device use and pain in the shoulders and neck; total time spent using a mobile device on a typical day was significantly associated with any pain reported in the left shoulder … the right shoulder … and the neck.
A great deal of analysis and discussion of the study results are provided in the original research article, and interested readers are encouraged to access it (see reference, below) for complete details. The following is a summary of key findings:
- 137 of 140 (98%) of the study participants use a hand-held mobile device
participants used such devices for a mean time of 4.65 hrs/day (though the standard deviation (SD) was 5.67 hrs/day, indicating substantial variations in time using such devices)
- 104 students; 5.05 hrs/day
- 32 staff members; 3.01 hrs/day
For all participants, mean time/day spent:
- emailing, texting or instant messaging was 1.04 hrs/day
- scheduling was 0.31 hrs/day
- browsing the internet was 2.23 hrs/day
- making phone calls / talking on the phone was 0.97 hrs/day
- listening to music, watching videos and taking pictures was 2.13 hrs/day
- gaming was 1.29 hrs/day
- 84% reported at least some pain in at least one body part
pain in the right hand was most common at the base of the thumb:
- 17% reported slight pain
- 9% reported moderate pain
- 2% reported severe pain
pain the left hand was also most common at the base of the thumb:
- 15% reported slight pain
- 4% reported moderate pain
- 1% reported severe pain
pain of any severity:
- 68% in the neck
- 62% in the upper back
- 32% in the right elbow and lower arm
- 52% in the right shoulder
- 46% in the left shoulder
- 27% in the left elbow and lower arm
statistically significant associations were observed between:
- time spent gaming and pain in the middle of the right thumb and pain in the right shoulder
- time spent internet browsing and pain at the base of the right thumb
- time spent scheduling and pain in the left hand
- time spent on the phone and making phone calls, and numbness or tingling in the left hand
- time spent listening to music, watching videos and taking pictures, and pain in the neck
- time spent gaming and pain in the middle of the right thumb
- total time spent using a mobile device and pain in the left shoulder, the right shoulder, and the neck
Detailed methods are provided in the origianl article, referenced below. The following are highlights.
This cross-sectional design research was carried out at a Canadian university. Self-selected participants self-reported their daily use of mobile devices and self-reported pain symptoms through an internet based questionnaire. 104 students and 32 staff or faculty members participated in the study (80 females, 60 males). 94% were right hand dominant, and 26% use both thumbs to type (vs. one thumb typing)).
Exposure measures captured the time per day, for a typical day in the last week, that participants utilized a hand-held mobile device for various tasks defined as:
- email, texting or instant messaging
- internet browsing
- on the phone or making phone calls
- listening to music, watching videos and taking pictures
Outcome measures included pain in 18 different body parts (e.g., end of thumb, middle of thumb, base of thumb, etc.), measured on a 1-10 scale (0 no pain) and categorized for analysis in various ways, and reports of numbness or tingling (yes or no).
The researchers also collected information regarding possible confounders, including gender, university status, daily desktop computer or laptop and mouse use, and daily, then used that data to understand any possible confounding effects in their analysis.
The authors note that using a cross-sectional design with self-selected participation may bias their results. For example, could it be that people with health problems were more likely to participate? Or, is it possible that a lack of association in some body parts may be due to a "healthy student effect?"
They also recognize that self-reported exposures and a limited sample size could have effected their results.
Berolo, S., Wells, RP, and Amick III, BC, Musculoskeletal symptoms among mobile hand-held device users and their relationship to device use: A preliminary study in a Canadian university population, Applied Ergonomics, Volume 42, Issue 2, January 2011, Pages 371-378. Last accessed at http://www.sciencedirect.com/science/article/pii/S0003687010001249 on June 18, 2013.