The current study explored the association between smartphone usage duration and hand-grip, pinch-grip strength among young people. As expected, there was an inverse association between the aforementioned variables. After using weight and BMI as a confounding factor, the inverse association remained significant. The results indicate that longer duration of average daily smartphone usage was related to weaker hand-grip and pinch-grip strength.
Many studies reported reduced hand function as well as multiple musculoskeletal problems when high-frequency smartphone users compared against low-frequency smartphone users. A study compared median and ulnar nerve conduction velocity, forward head angle, neck pain, and hand-grip between two adolescents groups based on the duration of smartphone usage (group A which use smartphone < 4 hours/day vs group B which use smartphone > 4 hours/day) 14. The results showed that group B with a higher frequency of smartphone usage had weaker ulnar nerve conduction velocity, higher neck pain (on visual analogue scale), reduced forward head angle movement, whereas, no difference was found in hand-grip strength or median nerve conduction velocity. The methodology of grouping in the former study was not reported, as it is unknown how the duration of smartphone usage was determined. Although group B had lower hand-grip strength than group A, the difference between the two groups was not significant 14. Another study compared between two young adults groups over smartphones overuse (high, low) based on smartphone addiction scale with a non-smartphone users group as a control group, in which it was found that high-frequency smartphone users had enlarged median nerve, more pain at the thumb, decreased pinch strength and hand functions in comparison to low-frequency smartphone users 8. With regards to the reduction of hand and pinch strength and overall hand performance among children, similar results were reported among high-frequency smartphone users 11. Majority of the former studies reported adverse effects of smartphone overuse over the hands, neck, median and ulnar nerve integrity. The question is whether these effects can be corrected or reduced with treatment or not.
Longitudinal studies investigating the effects of management to reduce the effect of smartphone overuse are limited. A study among 100 young adults investigated the effect of exercise training program and postural correction on hand-grip strength, pinch-grip strength, upper extremity disability 15. The study reported significant improvement in hand-grip strength, pinch-grip strength after a 12-week exercise program. The result of this study may indicate that increased smartphone usage is linked to the weakness of the hand-grip and pinch-grip, hence, with training, these variables improved. The current study reported this association between smartphone usage duration and hand-grip and pinch-grip strength.
The inverse association between smartphones usage duration and hand-grip pinch-grip strength can be explained due to the median nerve damage (enlargement) which was found to be associated with prolonged use of smartphones 8. The median nerve controls the flexor-pronator muscles in the forearm and most of the musculature present in the radial portion of the hand which include the abduction of the thump, flexion of the hand and wrist, flexion of the digital phalanx of fingers 16. The position of the hand and the thumb which is adapted while holding the smartphone for a prolonged duration may affect the median nerve 5. Additionally, the repetitive flexion and extension of the wrist and excessive use of the thumb may also damage the median nerve 9. Eventually, the damaged median nerve may lead to weakness of the muscles innervated by the median nerve, in which these muscles are the ones responsible for hand-grip and pinch-grip action.
To the best of knowledge, this is the first study that utilized the technology provided by the smartphones which enable the users to monitor their daily average use of the smartphone in the form of weekly reports. This method of direct measurement of smartphone usage duration has been used before to examine the relationship between screen time over smartphone and sleep quality 17. Although screen time can involve the duration of just merely looking at the screen, simple browsing over the phone will at least require the use of the thumb and the use of the palm to hold the smartphone (e.g. scrolling up and down over a page). Unlike filling a scale such as smartphone addiction scale, the method used in the current study allow participants to self-monitor their daily average smartphones activity weekly without the need of filling scales. This may also give an advantage of less time consumption for the health care professionals to advise targeted individuals about reducing their smartphones usage.
Clinically, this study adds to the literature and fill the gap in the knowledge about the relationship between smartphone usage duration and hand-grip, and pinch-grip strength. This would help health care professionals to establish preventive strategies or educational strategies to overcome the adverse effects of prolonged use of smartphones, especially at the younger ages. Further, the novelty in this study that using smartphone own monitoring system to detect the duration of the use of the phone may give a less time-consuming “more objective” option to use it instead of smartphone addiction scale. This can be utilized during physical assessment performed by health care professionals, especially with hand and wrist pathologies.
There are some limitations to the study. Due to the cross-sectional design of the study, causality between variables should not be assumed. The study was gender-biased and conducted only on males due to cultural reasons. Therefore, the generalizability of the data is limited to males in the same age categories. This warrant further research involving a female investigator and other age categories. Involvement of other daily tasks such as using keyboards on laptops may also influence hand-grip and pinch-grip strength. Thus, future research should also investigate other activities which involve the use of thumb and digitals of the hand during screening.
In conclusion, the current study demonstrated the inverse association between prolonged use of smartphones (using the smartphone own characteristics to monitor the screen time) with hand-grip and pinch-grip strength. The result indicates that longer use of smartphones was associated with weaker hand-grip and weaker pinch-grip. Young individuals should be aware of the negative impact of smartphones overuse on their hand functions.