A novel hypothesis-free multivariate screening methodology for the study of human exercise metabolism in blood serum is presented. Serum gas chromatography/time-of-flight mass spectrometry (GC/TOFMS) data was processed using hierarchical multivariate curve resolution (H-MCR), and orthogonal partial least-squares discriminant analysis (OPLS-DA) was used to model the systematic variation related to the acute effect of strenuous exercise. Potential metabolic biomarkers were identified using data base comparisons. Extensive validation was carried out including predictive H-MCR, 7-fold full cross-validation, and predictions for the OPLS-DA model, variable permutation for highlighting interesting metabolites, and pairwise t tests for examining the significance of metabolites. The concentration changes of potential biomarkers were verified in the raw GC/TOFMS data. In total, 420 potential metabolites were resolved in the serum samples. On the basis of the relative concentrations of the 420 resolved metabolites, a valid multivariate model for the difference between pre- and post-exercise subjects was obtained. A total of 34 metabolites were highlighted as potential biomarkers, all statistically significant (p < 8.1E-05). As an example, two potential markers were identified as glycerol and asparagine. The concentration changes for these two metabolites were also verified in the raw GC/TOFMS data. The strategy was shown to facilitate interpretation and validation of metabolic interactions in human serum as well as revealing the identity of potential markers for known or novel mechanisms of human exercise physiology. The multivariate way of addressing metabolism studies can help to increase the understanding of the integrative biology behind, as well as unravel new mechanistic explanations in relation to, exercise physiology.
Objective Sedentary behavior (SB) is defined as a mean of >6 hours of daytime sitting or lying down. SB has been shown to increase with older age and is a risk factor for disease. During the transition from working life to retirement, changes in daily life activities occur, risking increased SB. The aim of the present study was to gain a deeper understanding of SB in relation to the transition from working life to retirement as experienced by persons in retirement. Methods The study was grounded in a phenomenological life-world perspective. Fourteen semi-structured interviews were conducted with participants aged 64–75. Data were analyzed using the empirical phenomenological psychological method. Results The participants described that voluntary sedentary time was positively related to general health and well-being, while involuntary sedentary time was negatively related to health. Increased sedentary time was described as natural when aging. Retirement was expressed as a time for rest after hard work and the ability to choose a slower pace in life. Internal and external demands and daily routines interrupted SB, whereas loneliness was perceived to increase SB. Participants strived to find a balance between physical activity and sedentary time. The variations in the participants’ descriptions formed three typologies: in light of meaningful sedentary behavior, in the shadow of involuntary sedentary behavior, and a dual process – postponing sedentary behavior with physical activity. Conclusions Increased SB was perceived as natural when aging, but something that may be postponed by conscious choices. SB was perceived as associated with health, rest and recovery but also with the risk of deteriorating health. Impact This knowledge of the experienced meaning of SB could guide the design of health promotion interventions and may be helpful in targeting those in need of support and individualizing interventions to decrease SB in retirement. Lay Summary This study reveals how persons in retirement describe sedentary behavior as something healthy but also as unhealthy and that sedentary behavior is natural in aging and can be postponed by physical activity.
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