Edited by: Evangelos A. Christou, University of Florida, USA
Reviewed by: Evangelos A. Christou, University of Florida, USA; Hwasil Moon, Neuromuscular Physiology Lab, USA
*Correspondence: Mikko P. Tulppo, Department of Exercise and Medical Physiology, Verve, Kasarmintie 13, PO Box 404, FI-90101 Oulu, Finland e-mail:
This article was submitted to Exercise Physiology, a section of the journal Frontiers in Physiology.
This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
Bright light treatment has various positive psychophysiological effects. An acute improvement of cognitive performance in healthy subjects at night (Campbell and Dawson,
Timonen et al. raised the question of whether non-visual effects of light (like improved reaction time) could be partly mediated via a non-retinal pathway (Timonen et al.,
Psychomotor performance is an important determinant of performance in sports, specifically in those requiring fast decision making and execution skills. Also, particularly in professional sports, high strain due to the extremely busy competition schedule may result in decreased cognitive performance as an early marker of overreaching (Nederhof et al.,
Based on the alterations of baseline brain activity in the resting state in response to both increased light and a lack of light in the visual and sensorimotor networks, we hypothesized that sensorimotor function might be affected by ear light treatment. The aim of this study was to evaluate the effects of transcranial bright light treatment via the ear canals on cognitive performance in professional ice hockey players during the competition season. The bright light and sham interventions were organized during a very busy competition schedule during the dark time of the year (October 2011)—both components potentially resulting in overreaching. Secondly, we wanted to perform the study with one professional athletic team, since potential confusing factors like training load, competitions, and travel are virtually identical within the team. The treatments were given every morning throughout the study period and the protocol of the study was randomized, double-blind, and placebo-controlled.
Psychomotor speed tests with audio and visual warning signals and a memory test were administered to a Finnish National Ice Hockey League team (Oulun Kärpät, players' age 25 ± 5, range 17–33 years) before and after 24 days of bright light or sham treatment. The study protocol consisted of a randomized, double-blind, placebo-controlled study design. The subjects were randomized into treatment (
The brain-targeted bright light treatment or sham treatment was given transcranially via ear canals by using the VALKEE NPT 1100 bright light device (Valkee Ltd, Oulunsalo, Finland). The device was approved as a medical device in the European Union on 30 March 2010 (certificate no VTT-C-7657-01-1143-461-11). The ability of the sham device to produce light was eliminated. Otherwise the sham device worked exactly the same way as the bright light device. In order to create a real sham design, the subjects were told that effective/treating wavelengths of light are not necessarily visible and it is not possible to decide externally whether the treatment device is a sham or not. The blue-based white light was produced by light-emitting diodes (LEDs) which were attached to earplugs. In order to optimize treatment adherence, daily light treatment or sham treatment was taken at home between 8 am and noon. Each treatment session lasted 12 min which is a recommended treatment time by Valkee Ltd. The duration of treatment was based on previous observations on effectiveness of bright light therapy via ear canals on mental wellness (Timonen et al.,
An experienced psychologist conducted all the psychomotor tests (Eka Roivainen). The speed tests were administered with a Vienna Test System (Schuhfried GmbH, Moedling, Austria) and the memory test with a Cantab Test (Cambridge Cognition, Cambridge, United Kingdom) at Verve in Oulu, Finland. The tests were administered to each individual at the same time of day before and after the intervention. The testing procedure started with a simple reaction time test. The Vienna Test System's simple reaction time test assesses reaction time and motor time in response to simple visual or acoustic signals (Figure
The quality of sleep (scale: 0–10) was studied every morning at home using a visual analog scale (VAS).
Standard statistical methods were used to calculate means, standard deviations, and standard errors. Normal Gaussian distribution of the data was verified by the Kolmogorov-Smirnov goodness-of-fit test (
The results of the psychomotor tests are shown in Table
Total time, ms | 256 ± 30 | 231 ± 36 | 253 ± 43 | 238 ± 57 | |
Reaction time, ms | 135 ± 33 | 137 ± 32 | 136 ± 30 | 134 ± 45 | |
Motor time, ms | 128 ± 43 | 94 ± 26 |
121 ± 23 | 110 ± 32 | |
Total time, ms | 206 ± 37 | 198 ± 33 | 207 ± 31 | 201 ± 23 | |
Reaction time, ms | 96 ± 37 | 98 ± 37 | 101 ± 30 | 101 ± 31 | |
Motor time, ms | 110 ± 33 | 100 ± 31 | 109 ± 20 | 104 ± 23 | |
a.u. | 7.8 ± 1.2 | 8.1 ± 1.2 | 7.8 ± 1.0 | 8.3 ± 0.9 |
The mean quality of sleep VAS scores during the treatment period were 6.3 ± 1.9 and 6.8 ± 1.9 for the treatment and sham groups, respectively (
The novel finding of the present study is that daily transcranial bright light treatment improves motor time with a visual warning signal in professional ice-hockey players measured in laboratory conditions. The finding is in line with altered resting state activity in both visual and sensorimotor networks, shown to occur during immediate light treatment and during repetitively occurring darkness-related SAD (Starck et al.,
It is widely accepted that conventional bright light treatment improves acutely cognitive performance, and particularly motor and reaction times, in healthy populations (Campbell and Dawson,
Improvement in psychomotor performance after acute bright light exposure has been shown to be moderately associated with melatonin suppression (Chellappa et al.,
The cascade, which converts photic energy into neural responses, is called phototransduction. Recent studies show that potentially photosensitive opsins are not only expressed in the mammalian retina, but also widely in the human brain (Kojima et al.,
The most advanced bright light exposure studies are using fMRI techniques to study in more detail the effects of bright light treatment on various brain areas (Vandewalle et al.,
The number of subjects in the present study was small which limits the statistical power of the results. However, we wanted to perform the study with one professional athletic team, since training load, competitions, and travel are virtually identical within the team. Our principle finding on group-differences in absolute changes in the motor time to visual stimulus was statistically significant only when adjusted for age, although evident tendency was observed without adjustments. We considered adjustment for age relevant because of the previous findings on declining motor speed with aging and significant correlation between the change of motor time to visual stimulus and age (
Transcranial bright light treatment via the ear canals may improves motor time with a visual warning signal in elite athletes, suggesting that brain tissue is responsive to direct light exposure.
Mikko P.Tulppo, Eka Roivainen, Arto J. Hautala, Antti M. Kiviniemi, and Vesa J. Kiviniemi have no conflicts of interests. Heidi Jurvelin works for Valkee Ltd, Juuso Nissilä is the company founder and a shareholder, and Timo Takala is a minor shareholder.
This work was partly supported by Valkee Ltd (Oulu, Finland).