The study by Barbusse et al. (2024) investigated how motor control of arm movements is affected by reversed gravity. It is commonly assumed that the central nervous system contains an internal gravity model, and that this model is used to optimize movements to minimize effort under the influence of gravity (e.g., Berret et al., 2008). Previously, the effect of decreased and increased gravity was investigated, and it was shown that people were able to adapt to this novel environment in a matter of minutes or days (e.g., Gaveau et al., 2011). Therefore, the authors investigated the effect of inverse gravity on motor control of arm movements.

In this study, an experiment was performed in which participants were placed in an inversion table and asked to perform as many pointing movements with their shoulder as possible in 12 blocks. In each block, the inversion table was placed either in the head-up or head-down position, and the position was switched every 35 seconds, starting from the head-up position. After 4 blocks, a 90 second break was taken. It was found that movement duration and amplitude did not significantly differ between both orientations. An analysis of the difference in time to peak acceleration, time to peak velocity, and time to peak deceleration between upward and downward movements revealed no significant difference for the peak acceleration, while for the peak velocity, the time difference was significantly smaller in the head-down than the head-up position, and for the peak deceleration, the time difference changed in the head-down position with the number of blocks, reaching a value more similar to the head-up (baseline) position.

The time to peak acceleration did not reverse for the head-down position, which showed that the central nervous system is not able to take advantage of gravity when it is placed in a head-down position, since it does not take advantage of the “free” acceleration provided by gravity. A longer exposure to inverse gravity might allow the body to adapt and re-optimize its internal gravity model to the new situation. The time difference was significantly different for the deceleration, but not for acceleration, which indicates that the movement was adapted mainly by feedback control, but that feedforward control remained largely the same. This further supports the conclusion that the central nervous system had not yet adapted its internal gravity model, and that re-optimization starts with adapting feedback control (Izawa et al., 2008). An important limitation is the discomfort that is experienced in the head-down position, which not only changes gravity, but also created negative physiological responses.

References

Denis Barbusse, Sarah Amoura, Jérémie Gaveau, Olivier White (2024) Feedback-driven adaptation of gravity-related sensorimotor control to an upside-down posture. OSF preprints, ver.3 peer-reviewed and recommended by PCI Health & Movement Sciences. https://doi.org/10.17605/OSF.IO/D9JPF.

Berret B, Darlot C, Jean F, Pozzo T, Papaxanthis C, Gauthier JP (2008) The inactivation principle: mathematical solutions minimizing the absolute work and biological implications for the planning of arm movements. PLoS computational biology, 4, e1000194. https://doi.org/10.1371/journal.pcbi.1000194

Gaveau J, Paizis C, Berret B, Pozzo T, Papaxanthis C (2011) Sensorimotor adaptation of point-to-point arm movements after spaceflight: the role of internal representation of gravity force in trajectory planning. Journal of Neurophysiology, 106, 620–629. https://doi.org/10.1152/jn.00081.2011

Izawa J, Rane T, Donchin O, Shadmehr R (2008) Motor adaptation as a process of reoptimization. The Journal of Neuroscience: The Official Journal of the Society for Neuroscience, 28, 2883–2891. https://doi.org/10.1523/JNEUROSCI.5359-07.2008

Despite public health campaigns, achieving recommended physical activity levels remains challenging. Investigating the factors influencing physical activity is essential for effective promotion. Habit strength is known to correlate with physical activity (Hagger, 2019), making habit formation a key intervention target. Newman et al. (2023) expand current knowledge on physical activity and habit strength. They investigate if habit strength and its association with behavior differ between organized and leisure-time physical activities. Given the broad definition of physical activity and individual differences in preferences, studying habit's influence on varied activities is crucial. The cross-sectional survey, spanning the UK, USA, Australia, and Switzerland, involves 120 young adults (mean age = 25) engaged in organized sports. Although self-report measures are used, excluding commuting and occupational activity, the study yields intriguing results: Authors find significant habit strength differences between organized sports and leisure-time activities, indicating potential distinctions in habit formation drivers. Investigating factors establishing habits in organized sports could inform broader interventions. Remarkably, the impact of habits on behavior is consistent across both activity types, suggesting a universal role of habits. Further analysis reveals stronger habit strength in team sports versus individual ones, with no behavior association difference. Diverse habit strength in organized versus leisure-time activities underscores the need for focused research. Understanding unique aspects of team sports that promote habituation can reshape interventions, aligning leisure activities with organized sports' characteristics.

References

Hagger, M. S. (2019). Habit and physical activity: Theoretical advances, practical implications, and agenda for future research. Psychology of Sport and Exercise, 42, 118–129. https://doi.org/10.1016/j.psychsport.2018.12.007

Newman, K., Forestier, C., Cheval, B., Zenko, Z., De Chanaleilles, M., Gardner, B., & Rebar, A. L. (2023). Comparing habit-behaviour relationships for organised versus leisure time physical activity. OSF Preprints, 1–11, version 4, peer-reviewed and recommended by Peer Community in Health & Movement Sciences. https://doi.org/10.31219/osf.io/x5e9d

Pregnancy has been shown to affect the quality, duration, and pattern of sleep (Paavonen et al., 2017; Reid et al., 2017). These changes have important implications, as insufficient sleep is associated with health problems and complications during labor. In line with studies investigating the general population, a few studies focused on pregnant smokers and have also shown a prevalence of sleep abnormalities (e.g., Danilov et al., 2022; Lange et al., 2018; Paavonen et al., 2017). Studies examining the role of passive smoking on sleep are rare, be it in the general population or in pregnant women. 

The aim of the Ciochon et al. study was to investigate the relationship between active or passive smoking and three types of sleep problems during pregnancy: difficulty falling asleep, difficulty staying asleep, and waking up too early. The authors hypothesized that pregnant women's exposure to smoking (active and passive) would increase their risk of sleep problems during pregnancy.

Participants were part of a larger study: the Corona Mums project, which included 3365 pregnant women from Poland, aged 18 to 43 years. These women completed an online questionnaire during the COVID-19 pandemic, from May 2020 to September 2021. The authors conducted multivariate logistic regressions that included the following control variables: socio-demographic, pregnancy-related variables, and psychological variables.

The results of the study showed that passive smoking is a risk factor for waking up too early, but they showed no evidence suggesting that active or passive smoking was related to any of the other sleep variables. The authors highlighted the roles of control variables included in the models. Specifically, sleep difficulties were related to age, place of residence, education, level of anxiety and depression in pregnant women, and the presence of nausea or vomiting. Further, in all the models, the level of anxiety, depression, and trimester of pregnancy (3rd trimester in comparison to 1st and 2nd) were significantly related to the risk of occurrence of sleep problems.

While only one of the six examined associations showed statistical significance, the findings are still useful in highlighting potential risks associated with passive smoking and sleep disturbances during pregnancy. The study also underscores the need for more comprehensive investigations, including direct measures of sleep quality, such as actigraphy or polysomnography, which are necessary to better understand the underlying mechanisms and to confirm the potential impacts of both active and passive smoking on sleep during pregnancy.

This article (Goubran et al., 2024) presents a comprehensive systematic review and meta-analysis examining the relationship between kinesiophobia and physical activity. The inclusion of multiple health conditions and diverse measures of physical activity and kinesiophobia provides a broad perspective on the issue. 

Kinesiophobia (i.e., an excessive, irrational, and debilitating fear of movement) is thought to contribute to negative affective associations towards physical activity and avoidance behaviors, leading to decreased engagement in physical activity. Thus, the relationship between kinesiophobia and physical activity merits further investigation, particularly in health conditions where physical activity has a preventative and/or therapeutic role. 

The results of this meta-analysis (k = 83, n = 12,278) indicate a small-to-moderate negative correlation between kinesiophobia and physical activity (r = −0.19; 95% CI: −0.26 to −0.13; I2 = 85.5%; p < 0.0001.) Substantial heterogeneity and publication bias were noted, but p-curve analysis suggested true effects. Notably, this finding was consistent across studies using both self-report and objective device-based measures, and there was no evidence of a moderating effect of different measurement instruments or physical activity outcomes. 

Subgroup analyses revealed that the negative association between kinesiophobia and physical activity is significant in patients with cardiac, rheumatologic, neurologic, or pulmonary conditions but not in those with chronic or acute pain. This latter finding underscores the need to distinguish kinesiophobia from pain. Understanding that the fear of pain, injury, or aggravating an underlying condition, rather than actual pain, is associated with physical inactivity is important to consider when developing interventions to promote physical activity. Tailored interventions that address kinesiophobia specific to different health conditions could enhance physical activity levels and improve health outcomes. Further research is needed to explore the mechanisms underlying kinesiophobia and evaluate the efficacy of targeted interventions to mitigate its impact. 

This article makes an important contribution to our understanding of the relationship between kinesiophobia and physical activity. It provides evidence that fear of movement can be a barrier to physical activity in certain health conditions and highlights the need for condition-specific approaches to address this issue. This work is highly relevant for clinicians, researchers, and public health policymakers aiming to improve physical activity levels and overall health outcomes in a variety of populations.

References

Goubran, M., Farajzadeh, A., Lahart, I.M., Bilodeau, M. & Boisgontier, M.P. (2024). Physical activity and kinesiophobia: A systematic review and meta-analysis. MedRxiv, version. 3 peer-reviewed and recommended by Peer Community in Health and Movement Science. https://doi.org/10.1101/2023.08.17.23294240