Anne Hecksteden

Irisin and exercise training in humans - results from a randomized controlled training trial.

BackgroundThe recent discovery of a new myokine (irisin) potentially involved in health-related training effects has gained great attention, but evidence for a training-induced increase in irisin remains preliminary. Therefore, the present study aimed to determine whether irisin concentration is increased after regular exercise training in humans.MethodsIn a randomized controlled design, two guideline conforming training interventions were studied. Inclusion criteria were age 30 to 60 years, <1 hour/week regular activity, non-smoker, and absence of major diseases. 102 participants could be included in the analysis. Subjects in the training groups exercised 3 times per week for 26 weeks. The minimum compliance was defined at 70%. Aerobic endurance training (AET) consisted of 45 minutes of walking/running at 60% heart rate reserve. Strength endurance training (SET) consisted of 8 machine-based exercises (2 sets of 15 repetitions with 100% of the 20 repetition maximum). Serum irisin concentrations in frozen serum samples were determined in a single blinded measurement immediately after the end of the training study. Physical performance provided positive control for the overall efficacy of training. Differences between groups were tested for significance using analysis of variance. For post hoc comparisons with the control group, Dunnett’s test was used.ResultsMaximum performance increased significantly in the training groups compared with controls (controls: ±0.0 ± 0.7 km/h; AET: 1.1 ± 0.6 km/h, P < 0.01; SET: +0.5 ± 0.7 km/h, P = 0.01). Changes in irisin did not differ between groups (controls: 101 ± 81 ng/ml; AET: 44 ± 93 ng/ml; SET: 60 ± 92 ng/ml; in both cases: P = 0.99 (one-tailed testing), 1−β error probability = 0.7). The general upward trend was mainly accounted for by a negative association of irisin concentration with the storage duration of frozen serum samples (P < 0.01, β = −0.33). After arithmetically eliminating this confounder, the differences between groups remained non-significant.ConclusionsA training-induced increase in circulating irisin could not be confirmed, calling into question its proposed involvement in health-related training effects. Because frozen samples are prone to irisin degradation over time, positive results from uncontrolled trials might exclusively reflect the longer storage of samples from initial tests.Trial registrationClinicaltrials.gov. Identifier: NCT01263522.

Pre-cooling and sports performance: a meta-analytical review.

Pre-cooling is used by many athletes for the purpose of reducing body temperature prior to exercise and, consequently, decreasing heat stress and improving performance. Although there are a considerable number of studies showing beneficial effects of pre-cooling, definite conclusions on the effectiveness of pre-cooling on performance cannot yet be drawn. Moreover, detailed analyses of the specific conditions under which pre-cooling may be most promising are, so far, missing. Therefore, we conducted a literature search and located 27 peer-reviewed randomized controlled trials, which addressed the effects of pre-cooling on performance. These studies were analysed with regard to performance effects and several test circumstances (environmental temperature, test protocol, cooling method, aerobic capacity of the subjects).Eighteen studies were performed in a hot (>26°C) environment and eight in a moderate. The cooling protocols were water application (n=12), cooling packs (n=3), cold drinks (n=2), cooling vest (n=6) and a cooled room (n=4). The following different performance tests were used: short-term, high-intensity sprints (n=2), intermittent sprints (n=6), time trials (n= 10), open-end tests (n=7) and graded exercise tests (n=2). If possible, subjects were grouped into different aerobic capacity levels according to their maximal oxygen consumption (

Association between postexercise hypotension and long-term training-induced blood pressure reduction: a pilot study.

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Irisin does not mediate resistance training-induced alterations in resting metabolic rate.

O2max): medium 55–65mL/kg/min (n= 11) and high >65 mL/kg/min (n=6). For all studies the relative changes of performance due to pre-cooling compared with a control condition, as well as effect sizes (Hedges’g) were calculated. Mean values were weighted according to the number of subjects in each study.Pre-cooling had a larger effect on performance in hot (+6.6%, g=0.62) than in moderate temperatures (+1.4%, g = 0.004). The largest performance enhancements were found for endurance tests like open-end tests (+8.6%, g=0.52), graded exercise tests (+6.0%, g=0.44) and time trials (+4.2%, g=0.44). A similar effect was observed for intermittent sprints (+3.3%, g = 0.43), whereas performance changes were smaller during short-term, high-intensity sprints (−0.5%, g = 0.03). The most promising cooling methods were cold drinks (+15.0%, g= 1.68), cooling packs (+5.6%, g = 0.70) and a cooled room (+10.7%, g = 0.49), whereas a cooling vest (+4.8%, g = 0.31) and water application (+1.2%, g = 0.21) showed only small effects. With respect to aerobic capacity, the best results were found in the subjects with the highest

Effects of Sodium Bicarbonate on High-Intensity Endurance Performance in Cyclists: A Double-Blind, Randomized Cross-Over Trial.

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Blood born miRNAs signatures that can serve as disease specific biomarkers are not significantly affected by overall fitness and exercise.

O2max (high +7.7%, g = 0.65; medium +3.8%, g = 0.27). There were four studies analysing endurance-trained athletes under time-trial conditions, which, in a practical sense, seem to be most relevant. Those studies found an average effect on performance of 3.7% (g = 0.48).In summary, pre-cooling can effectively enhance endurance performance, particularly in hot environments, whereas sprint exercise is barely affected. In particular, well trained athletes may benefit in a typical competition setting with practical and relevant effects. With respect to feasibility, cold drinks, cooling packs and cooling vests can be regarded as best-practice methods.

Associations between acute and chronic effects of exercise on indicators of metabolic health: a pilot training trial.

Objective:The interindividual variability in the efficacy of regular endurance exercise to lower blood pressure is high. Therefore, to optimize training prescriptions, predictors would be desirable. The main hypothesis of the present study was an association between postexercise hypotension after an exhaustive exercise test and chronic blood pressure reductions in response to an endurance training program. Design:Uncontrolled prospective training study. Setting:University department. Participants:Healthy untrained subjects were recruited by flyers. Inclusion criteria were age 30 to 60 years, body mass index 25 to 35 kg/m2, untrained status (<1 hour/week regular activity; V[Combining Dot Above]O2max < 45 mL·min−1·kg−1), blood pressure 150/95 mm Hg, nonsmoker; 14 subjects were included, 12 could be analyzed. Intervention:Walking/running 4 times per week at 60% heart rate reserve for 4 weeks. Main Outcome Measures:Difference in blood pressure from the initial resting value to 1 and 24 hours after the initial test (acute) and the resting value before the final test (chronic), respectively. Results:Initial resting systolic blood pressure was 134 ± 18 mm Hg. Values were significantly reduced at all time points thereafter (1 hour: 125 ± 13 mm Hg; 24 hours: 128 ± 12 mm Hg; final: 125 ± 18 mm Hg). Acute and chronic changes correlated significantly (1 hour: P = 0.003; r = 0.77; 24 hours: P = 0.017; r = 0.67). Results for diastolic blood pressure were comparable yet less pronounced. Conclusions:The magnitude of postexercise hypotension is a promising candidate for the prediction of individual blood pressure–related training efficacy. Easily determined, it might be used to improve training prescriptions. However, further studies are needed to assess predictive accuracy.

Recovery and Performance in Sport : Consensus Statement

PURPOSE This study aimed to investigate the effects of a 6-month preventive resistance training program on resting metabolic rate (RMR) and its associations with fat-free mass (FFM) and the newly described myokine irisin as two potential mechanistic links between exercise training and RMR. METHODS In a randomized controlled trial, 74 sedentary healthy male and female participants either completed 6 months of high-repetition resistance training 3 d·wk in accordance with the American College of Sports Medicine recommendations (RT: n = 37; 47 ± 7 yr; body mass index, 25.0 ± 3.4 kg·m) or served as controls (CO: n = 37; 50 ± 7 yr; body mass index, 24.2 ± 3.2 kg·m). Strength (one-repetition maximum), RMR (indirect calorimetry), body fat (caliper method), and serum irisin concentration (enzyme-linked immunosorbent assay) were measured before and after 6 months of training. RESULTS Training led to an increase in strength (one-repetition maximum leg press, 16% ± 7%; P < 0.001). RMR increased in RT (1671 ± 356 vs 1843 ± 385 kcal·d, P < 0.001) but not in CO (1587 ± 285 vs 1602 ± 294 kcal·d, P = 0.97; group-time interaction, P < 0.01). Body weight (RT, -0.5 ± 2.4 kg; CO, 0.1 ± 2.3 kg), body fat percentage (RT, -1.1% ± 2.5%; CO, -0.7% ± 2.9%), and FFM (RT, 0.4 ± 2.1 kg; CO, 0.6 ± 1.9 kg) did not develop differently between groups (group-time interaction: P = 0.29, P = 0.54, and P = 0.59, respectively). Serum irisin concentration increased in CO (70.8 ± 83.4 ng·mL, P < 0.001) but not in RT (22.4 ± 92.6 ng·mL, P = 0.67; group-time interaction, P < 0.01). The change in RMR was not associated with the change in FFM (r = -0.11, P = 0.36) or irisin (r = -0.004, P = 0.97). CONCLUSIONS Preventive resistance training elicits an increase in RMR. However, in contrast to currently discussed hypotheses, this increase does not seem to be mediated by training-induced changes in FFM or circulating irisin concentration, which casts doubt in the meaning of irisin for human energy balance.

A New Method to Individualize Monitoring of Muscle Recovery in Athletes

Background While the ergogenic effect of sodium bicarbonate (BICA) on short-term, sprint-type performance has been repeatedly demonstrated, little is known about its effectiveness during prolonged high-intensity exercise in well-trained athletes. Therefore, this study aims to examine the influence of BICA on performance during exhaustive, high-intensity endurance cycling. Methods This was a single-center, double-blind, randomized, placebo-controlled cross-over study. Twenty-one well-trained cyclists (mean ± SD: age 24±8 y, BMI 21.3±1.7, VO2peak 67.3±9.8 ml·kg−1·min−1) were randomly allocated to sequences of following interventions: oral ingestion of 0.3 g·kg−1 BICA or 4 g of sodium chloride (placebo), respectively. One h after ingestion subjects exercised for 30 min at 95% of the individual anaerobic threshold (IAT) followed by 110% IAT until exhaustion. Prior to these constant load tests stepwise incremental exercise tests were conducted under both conditions to determine IAT and VO2peak. Analysis of blood gas parameters, blood lactate (BLa) and gas exchange measurements were conducted before, during and after the tests. The main outcome measure was the time to exhaustion in the constant load test. Results Cycling time to exhaustion was improved (p<0.05) under BICA (49.5±11.5 min) compared with placebo (45.0±9.5 min). No differences in maximal or sub-maximal measures of performance were observed during stepwise incremental tests. BICA ingestion resulted in an increased pH, bicarbonate concentration and BLa before, throughout and after both exercise testing modes. Conclusion The results suggest that ingestion of BICA may improve prolonged, high-intensity cycling performance. Trial Registration German Clinical Trials Register (DRKS) DRKS00006198.

Blood-Borne Markers of Fatigue in Competitive Athletes - Results from Simulated Training Camps.

Blood born micro(mi)RNA expression pattern have been reported for various human diseases with signatures specific for diseases. To evaluate these biomarkers, it is mandatory to know possible changes of miRNA signatures in healthy individuals under different physiological conditions. We analyzed the miRNA expression in peripheral blood of elite endurance athletes and moderatly active controls. Blood drawing was done before and after exhaustive exercise in each group. After Benjamini-Hochberg adjustment we did not find any miRNA with significant p-values when comparing miRNA expression between the different groups. We found, however, 24 different miRNAs with an expression fold change of minimum 1.5 in at least one of the comparisons (athletes before vs after exercise, athletes before exercise vs controls and athletes after exercise vs controls). The observed changes are not significant in contrast to the expression changes of the blood born miRNA expression reported for many human diseases. These data support the idea of disease associated miRNA patterns useful as biomarkers that are not readily altered by physiological conditions.