[Paracrine and endocrine functions of muscles]. / Die parakrine und endokrine Funktion der Muskulatur.

BACKGROUND: Myokines discharged from working muscles are intensively researched in view of rising importance of preventive and secondary preventive effects of the autocrine, paracrine and endocrine functions. OBJECTIVES: Recording of the current state of knowledge on the paracrine and endocrine effects of myokines and evaluation of training measures to optimize myokine concentration. METHOD: A selective database-driven literature search was carried out on myostatin, interleukin-6 (IL-6), interleukin-15 (IL-15), irisin, cathepsin B, brain-derived neurotrophic factor (BDNF), meteorin-like and kynurenine for the period 2011 until June 2021. The paracrine and endocrine effects of the myokines are analyzed. Their release after acute physical stress and training is described. RESULTS: IL-6 and IL-15 act in lipid metabolism and carbohydrate metabolism, IL-6 also in the brain and immune system. Irisin produces a conversion of white to brown adipose tissue ("browning"), so does meteorin-like. Cathepsin B has a central effect. Kynurenine acts indirectly via kynurenic acid in the brain. The secretion of myokines depends on the intensity of physical stress and is modified by training. Prevention of vascular and neurologic diseases, cognitive enhancement and increased immunological function can be reached by setting free myokines during physical activity. Therapeutical use by technologically modified myokines is proposed in metabolic and neurological diseases, immobilization and sarcopenia. CONCLUSIONS: The current research situation on myokines gives reason to recommend regular muscular activity in addition to the previously evidence-based benefits of sport in order to achieve preventive and therapeutic effects.

[Current aspects on nutrition in hypercholesterolemia]. / Aktuelle Aspekte zur Ernährung bei Hypercholesterinämie.

BACKGROUND: New European and American guidelines for nutrition in hypercholesterolemia coincided with a lowered target value for LDL(Low density lipoprotein)-cholesterol. METHODS: Guidelines, their development and supporting meta-analyses were searched in Medline/PubMed and Cochrane database and analyzed for the influence of fat, carbohydrates and protein on reduction of LDL-cholesterol as well as the differences between European and American guidelines. RESULTS: In contrast to European guidelines, American guidelines increasingly refrain from controlling fat in nutrition, based on studies on the influence of nutrition on LDL-cholesterol and saturated fat; instead, monosaccharides and disaccharides are to be reduced from 15% to 10% of total calories for avoidance of high LDL-cholesterol and a non-alcoholic fatty liver. In predisposed persons the ratio of triglycerides to HDL-cholesterol should be checked when controlling LDL-cholesterol, an early indicator of type 2 diabetes mellitus and non-alcoholic fatty liver disease. Substituting animal fat with plant fat hardly influences LDL-cholesterol. Whole fat milk should be consumed as a source of protein. The nutritional pattern is more important than single components. CONCLUSION: Fat content in nutrition is increasingly less important in hypercholesterolemia but the reduction of monosaccharides and disaccharides gains importance.

The Optimal Weight Carriage System for Runners: Comparison Between Handheld Water Bottles, Waist Belts, and Backpacks.

In endurance running, where fluid and nutritional support is not always readily available, the carriage of water and nutrition is essential. To compare the economy and physiological demands of different carriage systems, 12 recreational runners (mean age 22.8 ± 2.2 years, body mass index 24.5 ± 1.8 kg m-2, VO2max 50.4 ± 5.3 ml kg-1 min-1), completed four running tests, each of 60-min duration at individual running speeds (mean running speed 9.5 ± 1.1 km h-1) on a motorized treadmill, after an initial exercise test. Either no load was carried (control) or loads of 1.0 kg, in a handheld water bottle, waist belt, or backpack. Economy was assessed by means of energy cost (CR), oxygen cost (O2 cost), heart rate (HR), and rate of perceived exertion (RPE). CR [F(2,20) = 37.74, p < 0.01, ηp 2 = 0.79], O2 cost [F(2,20) = 37.98, p < 0.01, ηp 2 = 0.79], HR [F(2,18) = 165.62, p < 0.01, ηp 2 = 0.95], and RPE [F(2,18) = 165.62, p < 0.01, ηp 2 = 0.95] increased over time, but no significant differences were found between the systems. Carrying a handheld water bottle, waist belt, or backpack, weighing 1.0 kg, during a 60-min run exhibited similar physiological changes. Runners' choice may be guided by personal preference in the absence of differences in economy (CR, O2 cost, HR, and RPE).

A comparison of economy between two different backpack designs for runners.

We compared two backpack designs (back/front or back only) in twelve recreational runners (age 22.0 ± 1.7years). An initial incremental exercise test (VO2max 52.2 ± 4.7 ml kg-1.min-1) was conducted, followed by four tests of 20 min duration (running speed 9.8 ± 1.1 km/h) with loads carried of 0, 1 kg, 3 kg, and 6 kg with the two backpack designs in a randomized order. Economy was assessed by energy cost of running (CR), oxygen cost (O2 cost), heart rate (HR) and rate of perceived exertion (RPE). Repeated measure ANOVA revealed a non-significant main effect for CR, O2 cost, HR, RPE between systems. Post-hoc comparison of significant time × position interaction showed for CR, F(3,33) = 5.34, p < .01, ηp2 = 0.33, and O2 cost, F(3,33) = 5.15, p < .01, ηp2 = 0.32, that carrying weight in the back/front were significantly lower after 20 min (CR: p = .02 and O2 cost: p = .03). These results suggest, that for longer runs the equal distribution of weight is advantageous.

Predicting Competition Performance in Short Trail Running Races with Lactate Thresholds.

Trail running is a popular sport, yet factors related to performance are still not fully understood. Lactate thresholds have been thoroughly investigated in road running and correlate strongly with race performance, but to date few data are available about the value in trail running performance prediction. We examined 25 trail runners (age 31.2 ± 5.1 years, BMI 22.2 ± 1.82 kg/m2) with an initial graded exercise test for measurement of VO2max (59.5 ± 5.2 ml.kg-1.min- 1) and lactate thresholds (LT): LTAET (LT aerobic) 1.03 ± 0.59 mmol/l; 11.2 ± 1.1 km/h), IAT (individual lactate threshold) (2.53 ± 0.59 mmol/l; 15.4 ± 1.6 km/h) and LT4 (lactate threshold at 4 mmol/l) (16.2 ± 1.9 km/h). All runners subsequently participated in a 31.1 km XS trail race and 9 runners in a 21 km XXS trail race. Race performance times correlated negatively with the XS trail run (LTAET: r = -0.65, p < 0.01; LT4: r = -0.87, p < 0.01; IAT: r = -0.84, p < 0.01) and regression analysis showed that race performance could be predicted by: LT4: -324.15×LT4+13195.23 (R2 = .753, F1,23 = 70.02, p < 0.01). A subgroup analysis showed higher correlations with race performance for slower than faster runners. No correlations were found with the XXS race. Lactate thresholds can be of value in predicting trail race performance and help in designing training plans.

Running economy and energy cost of running with backpacks.

BACKGROUND: Running is a popular recreational activity and additional weight is often carried in backpacks on longer runs. Our aim was to examine running economy and other physiological parameters while running with a 1-kg and 3-kg backpack at different submaximal running velocities. METHODS: Ten male recreational runners (age 25±4.2 years, VO2peak 60.5±3.1 mL/kg/min) performed runs on a motorized treadmill of 5 minutes durations at three different submaximal speeds of 70, 80 and 90% of anaerobic lactate threshold (LT) without additional weight, and carrying a 1-kg and 3-kg backpack. Oxygen consumption, heart rate, lactate and RPE were measured and analyzed. RESULTS: Oxygen consumption, energy cost of running and heart rate increased significantly while running with a backpack weighing 3 kg compared to running without additional weight at 80% of speed at lactate threshold (sLT) (P=0.026, P=0.009 and P=0.003) and at 90% sLT (P<0.001, P=0.001, and P=0.001). Running with a 1-kg backpack showed a significant increase in heart rate at 80% sLT (P=0.008) and a significant increase in oxygen consumption and heart rate at 90% sLT (P=0.045 and P=0.007) compared to running without additional weight. Also running at 70% sLT running economy and cardiovascular effort increased with weighted backpack running compared to running without additional weight, however these increases did not reach statistical significance. CONCLUSIONS: Running economy deteriorates and cardiovascular effort increases while running with additional backpack weight especially at higher submaximal running speeds. Backpack weight should therefore be kept to a minimum.

Predicting Trail-Running Performance With Laboratory Exercise Tests and Field-Based Results.

PURPOSE: Trail running is a complex sport, and performance prediction is challenging. The aim was to evaluate 3 standard laboratory exercise tests in trail runners and correlate measurements to the race time of a trail competition evaluating its predictive power. METHODS: Nine competitive male trail runners (mean age: 31 [5.8] y) completed 3 different laboratory exercise tests (step, ramp, and trail tests) for determination of maximal oxygen uptake (VO2max), vVO2max, ventilatory (VT) and lactate thresholds (LT), mechanical power output, and running economy (RE), followed by a 31-km trail race. Runners had previously participated in the same race (previous year) and finished in the top 2%. Finishing times (dependent value) were tested in multiple-regression analysis with different independent value combinations. RESULTS: Linear-regression analysis revealed that variables measured during step and ramp tests significantly predicted performance. Step-test variables (speed at individual anaerobic threshold 16.4 [1.7] km/h and RE 12 km/h in %VO2max 65.6% [5.4%]) showed the highest performance prediction (R2 = .651, F2,6 = 5.60, P = .043), followed by the ramp test (vVO2max 20.3 [1.3] km/h; R2 = .477, F1,7 = 6.39, P = .04) and trail test (maximal power 3.9 [0.5] W/kg, VO2max 63.0 [4.8] mL O2·kg-1·min-1, vVT1 11.9 [0.7] km/h; R2 = .68, F3,5 = 3.52, P = .11). Adding race time from the preceding year to the step test improved the predictive power of the model (R2 = .988, F3,5 = 66.51, P < .001). CONCLUSIONS: The graded exercise test (VO2max, individual anaerobic threshold, and RE) most accurately predicted a 31.1-km trail-running performance. Combining submaximal intensities (individual anaerobic threshold and RE) with the previous year's race time of that specific event increased the predictive power of the model to 99%.

VO2max Testing in Trail Runners: Is There a Specific Exercise Test Protocol?

Trail running places specific physiological demands on the human body due to its uphill and downhill running sections. We developed and investigated a more sport-specific trail exercise test protocol (inclination and speed incremental protocol), and compared it to two standard exercise test protocols (horizontal step and ramp protocol) in thirteen highly trained trail runners (age 31±6 years, height 179±6.4 cm, weight 69.2±7.9 kg, BMI 21.6±2.1 kg/m2). The maximum oxygen uptake (VO2max) measured during the trail test (62.5±5.9 ml·kg-1·min-1, [95% CI: 59.0-66.1]) was significantly higher compared to both the step test (60.1±5.3 ml·kg-1·min-1, [95% CI: 56.8-63.3], p=0.024) and the ramp test (59.7±5.5 ml·kg-1·min-1, [95% CI: 56.4-63.0], p=0.028). Time to task failure was significantly shorter in the trail test (557±73 s, [95% CI: 512-601]) compared to both the step test (1378±152 s, [95% CI: 1286-1470], p<0.001) and the ramp test (605±95, [95% CI: 547-662], p<0.001). Other physiological measurements obtained were similar. The trail test was the preferred choice in our group of trail runners. This study supports the implementation of the trail test in practice, and recommends that its validity be evaluated further.

Changes in Running Economy During a 65-km Ultramarathon.

Purpose: Running economy (RE), expressed as oxygen cost (O2 cost) and energy cost of running (Cr) is important in ultramarathon (UM) running as it can help predict race performance. Controversy remains if RE increases, decreases, or remains stable in UM running. We examined RE before, during, and after a 65-km UM. Methods: 15 male UM runners (mean age 45 ± 5.7 years) completed a standard exercise test (mean VO2max 48.8 ± 3.4 ml⋅kg-1⋅min-1) for determination of the individual testing speed (60% VO2max: mean speed 9.4 ± 0.7 km/h). This was followed by a 65-km UM (elevation ± 1093 m) consisting of three laps (each 21.7 km). Pre and post indirect calorimetry measurements at individual running speed on the treadmill at UM-specific slopes (average percentage of positive and negative elevation) at -3, +3%, and level grade were performed in randomized order on a motorized treadmill in the laboratory for calculation of RE. Additionally after each lap, testing at +3% took place. Results: The O2 cost, Cr, and RER increased significantly pre to post UM (p < 0.01). During the uphill running, a main effect of distance indicated a gradual, linear increase in O2 cost, F(2,28) = 5.81, p < 0.01, η p 2 = 0.29, and Cr, F(2,28) = 5.96, p = 0.01, η p 2 = 0.30. Conclusion: O2 cost and Cr increased significantly pre to post UM in all testing conditions as well as during the uphill testing throughout the UM. This is the first study to demonstrate a consistent increase in O2 cost and Cr among a range of different slopes, at individual running speeds and race-specific slopes giving further evidence that these measures of RE increase in UM running.

Acute effects of whole-body vibration on trunk and neck muscle activity in consideration of different vibration loads.

The intention of this study was to systematically analyze the impact of biomechanical parameters in terms of different peak-to-peak displacements and knee angles on trunk and neck muscle activity during whole-body vibration (WBV). 28 healthy men and women (age 23 ± 3 years) performed four static squat positions (2 peak-to-peak displacements x 2 knee angles) on a side alternating vibration platform with and without vibration stimulus. Surface electromyography (EMG) was used to record the neuromuscular activity of the erector spinae muscle, the rectus abdominis muscle, and of the splenius muscle. EMG levels normalized to maximal voluntary contractions ranged between 3.2 - 27.2 % MVC during WBV. The increase in muscle activity caused by WBV was significant, particularly for the back muscles, which was up to 19.0 % MVC. The impact of the factor 'condition' (F-values ranged from 13.4 to 132.0, p ≤ 0.001) and of the factor 'peak-to-peak displacement' (F-values ranged from 6.4 to 69.0 and p-values from < 0.001 to 0.01) were statistically significant for each muscle tested. However, the factor 'knee angle' only affected the back muscles (F-value 10.3 and 7.3, p ≤ 0.01). The results of this study should give more information for developing effective and safe training protocols for WBV treatment of the upper body. Key pointsThe maximum levels of muscle activity were significantly reached at high amplitudes at a vibration frequency of 30 Hz.WBV leads to a higher muscle activation of the lower back muscles than of the abdominal muscles.Both knee angles of 30° and 45° have similar effects on the vibration load and represent safe positions to prevent any actual harm.Certain combinations of the biomechanical variables have similar effects on the level of muscle activity.

[Epidemiological evidence for preventing prostate cancer by physical activity]. / Epidemiologische Evidenz zur Prävention des Prostatakarzinoms durch körperliche Aktivität.

BACKGROUND: Earlier reviews yielded contradictory results for reducing the risk of prostate cancer by physical activity. METHODS: 32 Cohort studies and 17 case control studies taking the ones up to 2001 and the ones up to 2010 together. Additionally, subgroups from studies analyzing aggressive carcinomas and those after the age of 65 were presented separately. RESULTS: In the mean, no risk reduction was found in earlier and in studies from the last 8 years with mostly imprecisely measured activity. In 7 studies with subgroups on aggressive forms a positive dose response relationship was documented, being significant in 3 studies. The subgroup over 65 years with high amount of physical activity yielded a significant effect in 3 studies. CONCLUSIONS: Physical activity in leisure and in work fails to be protective but substantial evidence exists for an effective prevention by intensive physical activity.

Differential effects of indoleamines on auditory choice reaction, selective attention, and pitch discrimination.

The indoleamines serotonin and melatonin (MT) affected visual processing such as choice reaction. This study determined whether the indoleamines influence the processing of auditory stimuli. Serotonergic activity was increased using citalopram (CIT). We compared effects of single doses of 40 mg CIT, 1 mg MT, and placebo (randomized double-blind, cross-over design) in 18 healthy men. The applied tests assessed auditory choice reaction, selective attention, and serial discrimination using pitch variations as stimuli in each task. CIT reduced the performance in choice reaction and selective attention but not discrimination. MT tended to reduce selective attention and to improve discrimination. The findings suggest that indoleamines had different effects on distinct kinds of auditory processing. Serotonergic activation improved visual choice reaction, whereas the opposite effect was found in the auditory domain. We conclude that disorders and drugs affecting the indoleamines must be considered differentially in the auditory and the visual system.

[Leisure-time sport activities and cardiac outpatient therapy in coronary patients]. / Freizeitsportaktivität und Herzgruppentherapie bei Koronarpatienten.

BACKGROUND: Exercise intensity in coronary patients is controlled by heart rate measurements. Very few investigations have compared the maximum heart rate in cardiac outpatient groups, in leisure-time sport activities, and especially in swimming. PATIENTS AND METHODS: Within different exercise conditions 21 coronary patients, nine in well-compensated cardiac condition joining a training group and twelve joining the exercise group with lower intensity, without signs of heart failure, engaged in an incremental bicycle ergometry. A six-lead ECG was derived at the same time with a 24-h ECG. The performance tolerance was measured by the pulse limit derived in 20 patients; one patient failed to show signs of subjective or objective ischemia. During a 24-h ECG monitoring, the patients took part in a 1-h standardized cardiac outpatient program, a standardized swimming program 4 x 25 m, and a typical self-selected leisure-time activity. RESULTS: The patients showed a peak work capacity of 2.2 W/kg and a symptom-free work capacity of 1.3 W/kg. The derived upper heart rate limit was passed during swimming by 19, during leisure-time activity by 16, and during cardiac outpatient program by two patients. The maximum of the mean overriding the limit occurred in leisure-time activity. Signs of ischemia occurred during ergometry in 15, during swimming training in ten patients, during leisure-time activity in eight, and during cardiac outpatient therapy in one. Arrhythmia < Lown IVa was documented on the ergometer in 15, during leisure-time sport activity in 15, during cardiac outpatient therapy in 17, and during swimming in eight patients. Arrhythmia Lown IVa occurred in one patient each during ergometry, leisure sports, and during the night. CONCLUSION: Coronary patients are in danger to exercise beyond the pulse limit during swimming and other leisure-time sports and not during cardiac outpatient therapy. The upper heart rate limit should be observed during swimming and other endurance leisure-time activities, and is of little importance during cardiac outpatient therapy.