As winter descends upon the northern hemisphere, it reminds us of the effects of temperature on human function. We all know temperature can impair human abilities, but under what conditions, and by how much? In this study, researchers from Taiwan explore the relationship between hand/finger dexterity and the factors of skin temperature, surface electromyography (EMG), and ambient condition.
In their introduction, the authors review related research noting that others have already demonstrated that exposure to cold can:
- impair hand performance;
- reduce tactile sensitivity;
- reduce tracking performance;
- lead to increased accidents.
In their discussion, they cite the work of other cold temperature research in more detail, and readers who have a deeper interest in this topic are encouraged to review the original article, cited below.
Study Methods
- Utilized the "cold pressor test," which uses a water bath to induce temperature;
- two dexterity tasks were evaluated:
- Fine (Purdue pgboard test, requiring subjects to pickup and insert a small pin into a small hole);
- Gross (loosen nuts from a bolt using thumb, forefinger and middle finger);
- 24 healthy right-handed participants; average age of roughly 23-25 yrs; each task with 12 participants (6 males and 6 females);
- skin temperatures were measured at specific locations on the middle finger, hand and forearm;
- surface EMG measurements were recorded at specific locations over the extensor digitorums and flexor digitorum superficialis methods (baseline measurements were also recorded for calibration and normalization of data);
- A 40-min cooling stage though which participants immersed their right forearms in an 11 degrees C (52 degrees F) water tank; dexterity tests were performed at the 2nd, 10th, 18th, 26th, and 34th minutes; grip maximum voluntary contraction (MVC) was measured at the 40th minute.
- Immediately following the cooling stage, participants immersed their forearms in a 34 degrees C (93 degrees F) water bath for a 15 minute re-warming period; dexterity tests were performed at the 2nd, 7th and 12th minute; MVC was measured at the 15th minute;
Primary Findings
Gross Dexterity (nut loosening task):
- significant duration effect, with all participants showing reductions in gross dexterity as the length of cold exposure increased, and corresponding improvements during re-warming;
- significant gender effect, with males on average performing the task faster than females throughout the cooling and re-warming process;
- significant gender effect, with male dexterity not experiencing a significant performance decline until after 2 minutes of cold exposure;
- under study conditions, maximum reductions from baseline in dexterity of roughly 55% and 52% for males and females, respectively;
- skin temperatures showed significant decreases with cold exposure duration, and corresponding increases with re-warming, but showed no gender effect;
- the finger temperature showed the greatest temperature fluctuations; the finger and hand skin temperatures leveled off after 10 and 18 minutes of cold exposure, respectively, but the forearm temperature decreased continuously;
- the skin temperatures after 34 minutes of cold exposure averaged 12.5, 13.2, and 17.1 degrees C (55, 56, 63 degrees F) for the finger, hand and forearm, respectively;
- re-warming resulted in steady skin temperature increases to baseline for the finger and hand, and slightly below baseline for the forearm at the end of the 15 minute warming period.
Fine Dexterity (pin insertion task):
- only duration of exposure had a significant effect on performance;
- there was no gender effect, and performance steadily decreased over the 34 minute cooling period; and steadily increased, reaching baseline values, by the 12th minute of the warming period.
- the general trend of the normalized EMGs was downward for cooling, upward for warming; the effects of muscle and gender, and their interaction, we significant;
- the skin temperature effects for the fine dexterity task were very similar to those found in the gross dexterity task;
Grip Strength:
- gender and duration of exposure were significant;
- overall, MVC declined by 12% at the conclusion of the 40th minute of cold exposure, and returned to normal by the 15th minute of re-warming;
- baseline MVC for male participants was approximately 45% greater than female participants;
Note: This study also contains results regarding EMG measurements, which are of interest primarily to researchers, and are not discussed herein. Interested readers are encouraged to review the original article, cited below, for more details.
The Bottom Line — How this Applies To Ergonomists
There are indoor jobs, meat packing and other cold storage environments, for example, that necessarily expose workers to cold temperatures. There are also plenty of jobs that occur outdoors during cold temperatures, so it’s nice to have some evidence that can help ergonomists establish the effect of cold on hand dexterity.
After a lot of digging through this study, perhaps the most important finding is that skin temperature was the most consistent and best predictor for dexterity performance, accounting for 48-49% of performance variation. It’s not surprising that lower skin temperatures were associated with poorer performance, but studies like this give ergonomists some specifics that may help when convincing others. Being able to cite evidence that realistic cold conditions (e.g., ambient temperatures of 11 degrees C (52 degrees F) resulted in a 52-55% reduction in dexterity performance in this study can be powerful.
Knowing that cold temperatures effect performance is one thing, but finding solutions that improve such performance decrements is another. We have few options, and using gloves to keep the hands warm is one of the easiest and most prevalent. But, gloves can also create performance decrements, which will be the topic of our next research review.
Study Limitations
Like all studies, this one has significant limitations. For example, we cannot use this data to predict performance degradations over a spectrum of temperatures; these results apply to the specifics of these experimental conditions. Also, for example, the participants in this study were primarily younger, and there may be significant age effects that are therefore not revealed.
Reference
Chen, Wen-Lin; Shih, Yuh-Chuan; Chi, Chia-Fen, Hand and Finger Dexterity as a Function of Skin Temperature, EMG, and Ambient Condition, Human Factors, Volume 52, Number 3, June 2010 , pp. 426-440(15), Retrieved from http://www.ingentaconnect.com/content/hfes/hf/2010/00000052/00000003/art00005 on December 6, 2010.
This article originally appeared in The Ergonomics Report™ on 2010-12-06.