Associations between Acute and Chronic Effects of Exercise on Indicators of Metabolic Health: A Pilot Training Trial

Background The interindividual variability in the health-related efficacy of regular endurance training is high. This impedes on the individual optimization of preventive training prescriptions when optimal efficacy is intended. As a consequence, health-gains remain below what could be achieved. Practicable predictors of an individual’s responsiveness to physical exercise would offer a solution to this problem. Therefore, the present study aims to test the association of acute changes in indicators of metabolic health after an exhaustive exercise test and the respective chronic changes in response to an endurance training program. Methods Fasting blood samples of healthy, untrained, non-smoking subjects (n=12, age 49 ± 7 years; body mass index 29 ± 4; maximum oxygen uptake 34 ± 7 ml·min-1·kg-1) were collected before and 1 hour after an exhaustive exercise test as well as after a 4 week supervised training period (walking / running 4 times per week at 60 % heart rate reserve). Results A close linear relationship between acute and chronic changes could be demonstrated for insulin concentration (p=0.001; r=0.83), the fasting indicator of insulin sensitivity HOMA-IR (p<0.001; r=0.78) and non-esterified fatty acid concentration (p=0.001; r=0.88). No association became apparent for standard blood lipid parameters. Conclusion It is concluded that the magnitude of acute exercise-induced changes in indicators of insulin sensitivity and non-esterified fatty acid concentration is a promising candidate for the prediction of chronic training induced changes in the respective parameter. However, further studies are needed to assess predictive accuracy. Trial Registration www.clinicaltrials.gov NCT00934206 http://www.clinicaltrials.gov/ct2/show/NCT00934206


Introduction
Background 2 Scientific background and explanation of rationale Theories used in designing behavioral interventions

Methods
Participants 3 Eligibility criteria for participants, including criteria at different levels in recruitment/sampling plan (e.g., cities, clinics, subjects) Method of recruitment (e.g., referral, self-selection), including the sampling method if a systematic sampling plan was implemented Recruitment setting Settings and locations where the data were collected Interventions 4 Details of the interventions intended for each study condition and how and when they were actually administered, specifically including: Unit of assignment (the unit being assigned to study condition, e.g., individual, group, community) Method used to assign units to study conditions, including details of any restriction (e.g., blocking, stratification, minimization) Inclusion of aspects employed to help minimize potential bias induced due to non-randomization (e.g., matching) methods only 1) ( abstract methods introd. (1 intervention) (1 intervention) Associations between acute and chronic effects of exercise on indicators of metabolic health: a pilot training trial n.a.
All information for this category is given in the methods section.
n.a. n a n a n a Blinding (masking) 9 Whether or not participants, those administering the interventions, and those assessing the outcomes were blinded to study condition assignment; if so, statement regarding how the blinding was accomplished and how it was assessed.
Unit of Analysis 10 Description of the smallest unit that is being analyzed to assess intervention effects (e.g., individual, group, or community) If the unit of analysis differs from the unit of assignment, the analytical method used to account for this (e.g., adjusting the standard error estimates by the design effect or using multilevel analysis) Statistical Methods

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Statistical methods used to compare study groups for primary methods outcome(s), including complex methods of correlated data Statistical methods used for additional analyses, such as a subgroup analyses and adjusted analysis Methods for imputing missing data, if used Statistical software or programs used

Participant flow 12
Flow of participants through each stage of the study: enrollment, assignment, allocation, and intervention exposure, follow-up, analysis (a diagram is strongly recommended) o Enrollment: the numbers of participants screened for eligibility, found to be eligible or not eligible, declined to be enrolled, and enrolled in the study o Assignment: the numbers of participants assigned to a study condition o Allocation and intervention exposure: the number of participants assigned to each study condition and the number of participants who received each intervention o Follow-up: the number of participants who completed the followup or did not complete the follow-up (i.e., lost to follow-up), by study condition o Analysis: the number of participants included in or excluded from the main analysis, by study condition Description of protocol deviations from study as planned, along with reasons Recruitment 13 Dates defining the periods of recruitment and follow-up Baseline Data 14 Baseline demographic and clinical characteristics of participants in each study condition Baseline characteristics for each study condition relevant to specific disease prevention research Baseline comparisons of those lost to follow-up and those retained, overall and by study condition Comparison between study population at baseline and target population of interest Baseline equivalence 15 Data on study group equivalence at baseline and statistical methods used to control for baseline differences 4 n a n a n a n.a All information for this category is given in the results section.
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TREND Statement Checklist
Numbers analyzed 16 Number of participants (denominator) included in each analysis for each study condition, particularly when the denominators change for different outcomes; statement of the results in absolute numbers when feasible Indication of whether the analysis strategy was "intention to treat" or, if not, description of how non-compliers were treated in the analyses Outcomes and estimation 17 For each primary and secondary outcome, a summary of results for each estimation study condition, and the estimated effect size and a confidence interval to indicate the precision Inclusion of null and negative findings Inclusion of results from testing pre-specified causal pathways through which the intervention was intended to operate, if any Ancillary analyses 18 Summary of other analyses performed, including subgroup or restricted analyses, indicating which are pre-specified or exploratory Adverse events 19 Summary of all important adverse events or unintended effects in each study condition (including summary measures, effect size estimates, and confidence intervals)

Interpretation 20
Interpretation of the results, taking into account study hypotheses, sources of potential bias, imprecision of measures, multiplicative analyses, and other limitations or weaknesses of the study Discussion of results taking into account the mechanism by which the intervention was intended to work (causal pathways) or alternative mechanisms or explanations Discussion of the success of and barriers to implementing the intervention, fidelity of implementation Discussion of research, programmatic, or policy implications Generalizability 21 Generalizability (external validity) of the trial findings, taking into account the study population, the characteristics of the intervention, length of follow-up, incentives, compliance rates, specific sites/settings involved in the study, and other contextual issues Overall Evidence

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General interpretation of the results in the context of current evidence and current theory From: Des Jarlais, D. C., Lyles, C., Crepaz, N., & the Trend Group (2004). Improving the reporting quality of nonrandomized evaluations of behavioral and public health interventions: The TREND statement. American Journal of Public Health, 94, 361-366. For more information, visit: http://www.cdc.gov/trendstatement/ n a n a n a All information for this category is given in the discussion section. n.a.