Postexercise Hypotension as a Predictor for Long-Term Training-Induced Blood Pressure Reduction: A Large-Scale Randomized Controlled Trial.

OBJECTIVE: To investigate the correlation between acute exercise effects and chronic training effects on blood pressure (BP). DESIGN: Randomized, controlled training study focusing on the optimization of preventive effects of physical training. SETTING: The study was performed in a university department. PARTICIPANTS: One hundred twenty-seven healthy, untrained subjects. INTERVENTION: Subjects were divided into 4 groups: interval endurance training (IET) (n = 26, 4 × 4 min at 95% maximal heart rate), continuous endurance training (CET) (n = 23, 45 minutes at 60% heart rate reserve), strength endurance training (SET) (n = 40, 8 machine-based exercises, each 2 x 15 repetitions at the 20 repetition maximum), and control (CON) (n = 38). In the 3 training groups, subjects trained 3 times a week for 6 months, the CON group was asked to retain their sedentary lifestyle. MAIN OUTCOME MEASURES: The acute exercise effect on BP was defined as the change of BP after an exhaustive stage test, compared with baseline. The chronic training effect on BP was determined as the change of resting BP after the 6-month training period. RESULTS: For CET, a significant correlation between acute and chronic effects on systolic (r = 0.66, P = 0.001) and diastolic (r = 0.66, P = 0.001) BP was observed. For SET, a significant correlation (r = 0.45, P = 0.007) was found only for diastolic BP. No significant correlations were found for IET. CONCLUSIONS: It can be assumed that postexercise hypotension is an easy-to-use predictor for the efficacy of CET to reduce BP, and may be a valuable tool for physicians to individualize prescribed training schedules for patients to reduce cardiovascular risk. TRIAL REGISTRATION: www.clinicaltrials.gov; ID: NCT01263522.

The effect of short-term interval training during the competitive season on physical fitness and signs of fatigue: a crossover trial in high-level youth football players.

PURPOSE: To analyze performance and fatigue effects of small-sided games (SSG) vs high-intensity interval training (HIIT) performed during a 4-wk in-season period in high-level youth football. METHODS: Nineteen players from 4 youth teams (16.5 [SD 0.8] y, 1.79 [0.06] m, 70.7 [5.6] kg) of the 2 highest German divisions completed the study. Teams were randomly assigned to 1 of 2 training sequences (2 endurance sessions per wk): One training group started with SSG, whereas the other group conducted HIIT during the first half of the competitive season. After the winter break, training programs were changed between groups. Before and after the training periods the following tests were completed: the Recovery-Stress Questionnaire for Athletes, creatine kinase and urea concentrations, vertical-jump height (countermovement jump [CMJ], drop jump), straight sprint, agility, and an incremental field test to determine individual anaerobic threshold (IAT). RESULTS: Significant time effects were observed for IAT (+1.3%, η(p)(2) = .31), peak heart rate (-1.8%, η(p)(2) = .45), and CMJ (-2.3%, η(p)(2) = .27), with no significant interaction between groups (P > .30). Players with low baseline IAT values (+4.3%) showed greater improvements than those with high initial values (± 0.0%). A significant decrease was found for total recovery (-5.0%, η(p)(2) = .29), and an increase was found for urea concentration (+9.2%, η(p)(2) = .44). CONCLUSION: Four weeks of in-season endurance training can lead to relevant improvements in endurance capacity. The decreases in CMJ height and total-recovery score together with the increase in urea concentration might be interpreted as early signs of fatigue. Thus, the danger of overtaxing players should be considered.

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

BACKGROUND: The 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. METHODS: In 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. RESULTS: Maximum 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-ß 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, ß = -0.33). After arithmetically eliminating this confounder, the differences between groups remained non-significant. CONCLUSIONS: A 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.