Effects of a 10-Week Exercise and Nutritional Intervention with Variable Dietary Carbohydrates and Glycaemic Indices on Substrate Metabolism, Glycogen Storage, and Endurance Performance in Men: A Randomized Controlled Trial.

BACKGROUND: Daily nutrition plays an important role in supporting training adaptions and endurance performance. The objective of this 10-week study was to investigate the consequences of varying carbohydrate consumption and the glycaemic index (GI) together with an endurance training regimen on substrate oxidation, muscle energy storage and endurance performance under free-living conditions. Sixty-five moderately trained healthy men (29 ± 4 years; VO2 peak 55 ± 8 mL min-1 kg-1) were randomized to one of three different nutritional regimes (LOW-GI: 50-60% CHO with ≥ 65% of these CHO with GI < 50 per day, n = 24; HIGH-GI: 50-60% CHO with ≥ 65% CHO with GI > 70 per day, n = 20; LCHF: ≤ 50 g CHO daily, n = 21). Metabolic alterations and performance were assessed at baseline (T0) and after 10 weeks (T10) during a graded exercise treadmill test. Additionally, a 5 km time trial on a 400-m outdoor track was performed and muscle glycogen was measured by magnet resonance spectroscopy. RESULTS: Total fat oxidation expressed as area under the curve (AUC) during the graded exercise test increased in LCHF (1.3 ± 2.4 g min-1 × km h-1, p < 0.001), remained unchanged in LOW-GI (p > 0.05) and decreased in HIGH-GI (- 1.7 ± 1.5 g min-1 × km h-1, p < 0.001). After the intervention, LOW-GI (- 0.4 ± 0.5 mmol L-1 × km h-1, p < 0.001) and LCHF (- 0.8 ± 0.7 mmol L-1 × km h-1, p < 0.001) showed significantly lower AUC of blood lactate concentrations. Peak running speed increased in LOW-GI (T0: 4.3 ± 0.4 vs. T10: 4.5 ± 0.3 m s-1, p < 0.001) and HIGH-GI (T0: 4.4 ± 0.5 vs. T10: 4.6 ± 0.4 m s-1), while no improvement was observed in LCHF. Yet, time trial performance improved significantly in all groups. Muscle glycogen content increased for participants in HIGH-GI (T0: 97.3 ± 18.5 vs. T10: 144.5 ± 39.8 mmol L wet-tissue-1, p = 0.027) and remained unchanged in the LOW-GI and the LCHF group. At the last examination, muscle glycogen concentration was significantly higher in LOW-GI compared to LCHF (p = 0.014). CONCLUSION: Changes in fat oxidation were only present in LCHF, however, lower lactate concentrations in LOW-GI resulted in changes indicating an improved substrate metabolism. Compared to a LCHF diet, changes in peak running speed, and muscle glycogen stores were superior in LOW- and HIGH-GI diets. The low GI diet seems to have an influence on substrate metabolism without compromising performance at higher intensities, suggesting that a high-carbohydrate diet with a low GI is a viable alternative to a LCHF or a high GI diet. TRIAL REGISTRATION: Clinical Trials, NCT05241730. https://clinicaltrials.gov/study/NCT05241730 . Registered 25 January 2021.

The oral contraceptive cycle and its influences on maximal and submaximal endurance parameters in elite handball players.

The usage of the oral contraceptive pill is widespread among athletes of various levels. However, there is limited knowledge on how the intake of the pill alters the submaximal and maximal endurance parameters between the oral contraceptive phases. Therefore, the aim of this study was to examine potential differences between the pill intake and withdrawal phase on endurance-related parameters in first-division handball players. In total, 15 female team handball players performed two graded exercise tests until volitional exhaustion on a motorized treadmill. Tests were performed during the pill intake (days 16-17) and withdrawal phase (day 2-3). Throughout the test, respiratory gases were measured breath-by-breath, and the heart rate was measured continuously. Before and after the graded exercise test, blood samples were obtained in order to assess the blood lactate concentration. Before each test, venous blood samples were taken to determine endogenous sex hormone levels. Ventilatory parameters (V˙O2, V˙CO2, and V˙E, and respiratory equivalents for V˙O2 and V˙CO2) were measured, and the oxidation of fat and carbohydrates was calculated. A paired-sample t-test was used to assess differences between the two time points, and the significance was accepted as p < 0.050. Significant differences with lower values during the consumption phase were found for absolute (mean difference ± SD: 88 ± 131 mL∙min-1; p = 0.021) and relative V˙O2peak (mean difference ± SD: 1 ± 2 mL∙min-1∙kg-1; p = 0.012). Higher values during the consumption phase were found for submaximal respiratory equivalents for V˙O2 (mean difference ± SD: -1.1 ± 1.7; p = 0.028) and V˙CO2 (mean difference ± SD: -0.9 ± 1.5; p = 0.032). No differences were found for all other parameters, including differences for endogenous sex hormones (p > 0.050). The results of the current study suggest only marginal and physiologically insignificant differences in endurance-related parameters between oral contraceptive phases.

Does a Physical Activity Intervention on Classroom-Based Ergometers During Teaching Lessons Effect Physical Fitness, Body Composition, and Health-Related Blood Parameters? A Pilot Cluster Randomized Controlled Study.

BACKGROUND: Time constraints comprise one limiting factor for implementing school-based physical activity programs. The aim of this pilot cluster randomized controlled study was to explore the effects of a cycle ergometer intervention during regular lessons on physical fitness, body composition, and health-related blood parameters. METHODS: Participants attended one of 2 classes selected from one school, which were randomly assigned to an intervention group (n = 23, 11.2 [0.5] y) consisting of cycling on classroom-based ergometers during 3 lessons per week at a self-selected intensity and a control group (n = 21, 11.3 [0.5] y) not receiving any treatment. Prior to and after the 5-month intervention period, physical fitness (with ventilatory threshold as primary outcome), body composition, and parameters of glucose and lipid metabolism were assessed. RESULTS: A significant time × group interaction was revealed for ventilatory threshold (P = .035), respiratory compensation point (P = .038), gross efficiency (P < .001), maximal aerobic power (P = .024), triglycerides (P = .041), and blood glucose levels (P = .041) with benefits for the intervention group. Peak oxygen uptake and body composition were not affected. CONCLUSIONS: Children's aerobic capacity benefited from the low-intensity school-based cycling intervention, while body composition and most blood parameters were not affected. The intervention using cycle ergometers is a feasible and time-saving strategy to elevate submaximal physical fitness.

Influence of an increased number of physical education lessons on the motor performance of adolescents-A non-interventional cohort study.

Increasing the amount of regular physical education lessons in school is currently discussed in many countries in order to increase physical activity in youth. The purpose of this study was to compare the motor performance of pupils from an observation group participating in a school trial of two additional physical education lessons (5 lessons of each 50 min/week) without a specific intervention program to a control group with a regular amount of three physical education lessons (3 lessons of each 50 min/week) as indicated by the standard Austrian school curriculum. In this cohort study motor performance of 140 adolescents (12.7±0.5 years) was assessed by means of the German Motor Performance Test 6-18 over a period of 1.5 years with measurement time points before (T1), after eight months (T2) and at the end of the observation period (T3). Two- and three-way mixed analysis of variance were used to detect time, group and interaction effects. Although the observation group demonstrated a higher total motor performance score at all time points (P = 0.005), the improvement over time in total motor performance (P < 0.001) was more pronounced in the control group. Girls and boys developed differently over time (time*gender interaction: P = 0.001), whereby group allocation did not affect this interaction (time*gender*group: P = 0.167). Anyway, girls of control group tend to benefit most of additional physical education lessons. Sports club members scored significantly higher in motor performance across the observation period (P = 0.018) irrespective of group allocation. These findings indicate that there could be a ceiling effect in what the pupils could achieve in terms of motor performance as the pupils of the observation group might have reached this point earlier than their counterparts in the control group. Nevertheless, sports club membership seems to reveal some benefits. Whether improving quality and specificity of the single physical lessons might be superior to merely adding additional ones needs to be confirmed in future studies.

Strength Performance Across the Oral Contraceptive Cycle of Team Sport Athletes: A Cross-Sectional Study.

Oral contraceptive pills (OCP) are very popular in female athletes not only for contraceptive effects but also due to the possibility of cycle manipulation. Moreover, it is debatable whether the manipulation of the menstrual cycle has a beneficial effect on exercise performance. Therefore, the aim of this study was to investigate potential differences in knee-extensor and flexor strength performance of first division team sport athletes between phases of the oral contraceptive cycle. Sixteen female handball players (age: 23.3 ± 3.1 years; body mass: 67.0 ± 8.52 kg; body stature: 1.68 ± 0.05 m) using a monophasic OCP participated in strength performance tests, once during OCP consumption (CONS) and once during withdrawal (WITH). Tests were performed on a dynamometer to measure knee-extensor and flexor maximal voluntary isokinetic and isometric torque. Prior to each test, body mass was assessed, and venous blood samples were collected. Wilcoxon signed-rank test and magnitude-based inferences have been conducted to analyze differences between WITH and CONS. Significance was accepted at P < 0.05. No significant differences between oral contraceptive cycle phases of knee-extensor and flexor strength parameters and body mass have been indicated (all at P > 0.05). Follicle-stimulating hormone (FSH) (P = 0.001) and luteinizing hormone (P = 0.013) were significantly higher in WITH, whereby estradiol and progesterone showed no significant difference between phases (both at P > 0.05). These results support the notion that knee-extensor and flexor isokinetic and isometric strength performance does not differ between phases of oral contraceptive cycle in well-trained team sport athletes. OCP intake is suggested to cause a stable but downregulated hormone cycle, which has no effect on knee-extensor and flexor strength when comparing oral contraceptive cycle phases. Therefore, manipulation of the female cycle using OCP in order to achieve a higher knee-extensor and flexor strength performance does not seem to be justified; however, it is currently unclear if cycle manipulation might affect other physiological systems.

A 30-Min Rest Protocol Does Not Affect W', Critical Power, and Systemic Response.

PURPOSE: This study aimed to assess and compare the systemic response of oxygen uptake kinetics and muscle deoxygenation between a 30-min rest protocol and a multivisit protocol on the parameters of the power-duration relationship (i.e., critical power [CP] and W'). METHODS: Nine endurance-trained triathletes reported to the laboratory on five occasions: a preliminary graded exercise test and a familiarization, a 30-min single-visit protocol (time trials of 10, 5, and 2 min in that order interspersed with 30 min rest), and a multivisit protocol (time trials of 10, 5, and 2 min in randomized order interspersed by >24 h rest). Heart rate (HR) was recorded continuously, respiratory gases were measured breath by breath, and deoxygenation was recorded at 10 Hz using near-infrared spectroscopy (NIRS) during all tests. Blood lactate (BLa-) concentration was measured before all time trials. Maximal HR (HRmax), oxygen uptake (V˙O2) during the first 2 min (V˙O2onset), mean response time, end-exercise V˙O2 (V˙O2peak), V˙O2 amplitude (amplV˙O2), O2 deficit, NIRS τ, amplitude (amplNIRS), and time delay were assessed. To compare the two protocols and to assess the differences in W' and CP, a paired sample t-test was used as well as a two-way ANOVA to assess the differences between trials and/or protocols, including trial-protocol interactions. RESULTS: No significant differences, and trivial effect sizes, were found for W' and CP between protocols (P = 0.106-0.114, d < 0.01-0.08). Furthermore, no significant differences between protocols were found for all parameters, except for [BLa-]. Significant differences between trials were found for V˙O2ampl, V˙O2onset, NIRS τ, amplNIRS, [BLa-], and HRmax. CONCLUSION: Results suggest that W' and CP can be determined using the 30-min rest protocol without confounding effects of previous severe exercise compared with the multivisit protocol.

Effects of course design (curves and elevation undulations) on marathon running performance: a comparison of Breaking 2 in Monza and the INEOS 1:59 Challenge in Vienna.

Eliud Kipchoge made two attempts to break the 2-hour marathon, in Monza and then Vienna. Here we analyse only the effects of course elevation profile and turn curvatures on his performances. We used publicly available data to determine the undulations in elevation and the radii of the curves on the course. With previously developed equations for the effects of velocity, slope, and curvature on oxygen uptake, we performed simulations to quantify how much the elevation changes and curves of the Vienna course affect a runner's oxygen uptake (at a fixed velocity) or velocity (at a fixed oxygen uptake). We estimate that, after the initial downhill benefit, the course led to an overall oxygen uptake penalty of only 0.03%. When compared to a perfectly level straight course, we estimate that the combined effects of the undulations and curves of the Vienna course incurred a penalty of just 1.37 seconds. Kipchoge ran 2:00:25 in Monza Italy. Comparison with the Monza course profile indicates a 46.2 second (1.09% oxygen uptake) advantage of Vienna's course while the fewer curves of Vienna contributed ~ 1 second. The Vienna course was very well-chosen because it minimized the negative effects of elevation changes and curves.Abbreviations: CoT: Oxygen cost of transport; CV˙O2: Curved rate of oxygen consumption; V˙O2: Rate of oxygen consumption; WA: World Athletics.

Relationship Between the Critical Power Test and a 20-min Functional Threshold Power Test in Cycling.

To investigate the agreement between critical power (CP) and functional threshold power (FTP), 17 trained cyclists and triathletes (mean ± SD: age 31 ± 9 years, body mass 80 ± 10 kg, maximal aerobic power 350 ± 56 W, peak oxygen consumption 51 ± 10 mL⋅min-1⋅kg-1) performed a maximal incremental ramp test, a single-visit CP test and a 20-min time trial (TT) test in randomized order on three different days. CP was determined using a time-trial (TT) protocol of three durations (12, 7, and 3 min) interspersed by 30 min passive rest. FTP was calculated as 95% of 20-min mean power achieved during the TT. Differences between means were examined using magnitude-based inferences and a paired-samples t-test. Effect sizes are reported as Cohen's d. Agreement between CP and FTP was assessed using the 95% limits of agreement (LoA) method and Pearson correlation coefficient. There was a 91.7% probability that CP (256 ± 50 W) was higher than FTP (249 ± 44 W). Indeed, CP was significantly higher compared to FTP (P = 0.041) which was associated with a trivial effect size (d = 0.04). The mean bias between CP and FTP was 7 ± 13 W and LoA were -19 to 33 W. Even though strong correlations exist between CP and FTP (r = 0.969; P < 0.001), the chance of meaningful differences in terms of performance (1% smallest worthwhile change), were greater than 90%. With relatively large ranges for LoA between variables, these values generally should not be used interchangeably. Caution should consequently be exercised when choosing between FTP and CP for the purposes of performance analysis.

Methodological Approaches and Related Challenges Associated With the Determination of Critical Power and Curvature Constant.

Muniz-Pumares, D, Karsten, B, Triska, C, and Glaister, M. Methodological approaches and related challenges associated with the determination of critical power and W'. J Strength Cond Res 33(2): 584-596, 2019-The relationship between exercise intensity and time to task failure (P-T relationship) is hyperbolic, and characterized by its asymptote (critical power [CP]) and curvature constant (W'). The determination of these parameters is of interest for researchers and practitioners, but the testing protocol for CP and W' determination has not yet been standardized. Conventionally, a series of constant work rate (CWR) tests to task failure have been used to construct the P-T relationship. However, the duration, number, and recovery between predictive CWR and the mathematical model (hyperbolic or derived linear models) are known to affect CP and W'. Moreover, repeating CWR may be deemed as a cumbersome and impractical protocol. Recently, CP and W' have been determined in field and laboratory settings using time trials, but the validity of these methods has raised concerns. Alternatively, a 3-minute all-out test (3MT) has been suggested, as it provides a simpler method for the determination of CP and W', whereby power output at the end of the test represents CP, and the amount of work performed above this end-test power equates to W'. However, the 3MT still requires an initial incremental test and may overestimate CP. The aim of this review is, therefore, to appraise current methods to estimate CP and W', providing guidelines and suggestions for future research where appropriate.

Differences in Muscle Metabolism Between Triathletes and Normally Active Volunteers Investigated Using Multinuclear Magnetic Resonance Spectroscopy at 7T.

Purpose: The influence of endurance training on skeletal muscle metabolism can currently be studied only by invasive sampling or through a few related parameters that are investigated by either proton (1H) or phosphorus (31P) magnetic resonance spectroscopy (MRS). The aim of this study was to compare the metabolic differences between endurance-trained triathletes and healthy volunteers using multi-parametric data acquired by both, 31P- and 1H-MRS, at ultra-high field (7T) in a single experimental protocol. This study also aimed to determine the interrelations between these MRS-derived metabolic parameters. Methods: Thirteen male triathletes and ten active male volunteers participated in the study. Proton MRS data from the vastus lateralis yielded concentrations of acetylcarnitine, carnosine, and intramyocellular lipids (IMCL). For the measurement of phosphodiesters (PDEs), inorganic phosphate (Pi), phosphocreatine (PCr), and maximal oxidative capacity (Qmax) phosphorus MRS data were acquired at rest, during 6 min of submaximal exercise and following immediate recovery. Results: The triathletes exhibited significantly higher IMCL levels, higher initial rate of PCr resynthesis (VPCr) during the recovery period, a shorter PCr recovery time constant (τPCr), and higher Qmax. Multivariate stepwise regression analysis identified PDE as the strongest independent predictor of whole-body maximal oxygen uptake (VO2max). Conclusion: In conclusion, we cannot suggest a single MRS-based parameter as an exclusive biomarker of muscular fitness and training status. There is, rather, a combination of different parameters, assessable during a single multi-nuclear MRS session that could be useful for further cross-sectional and/or focused interventional studies on skeletal muscle fitness and training effects.

Different durations within the method of best practice affect the parameters of the speed-duration relationship.

The aim of the study was to determine whether estimates of the speed-duration relationship are affected using different time-trial (TT) field-based testing protocols, where exhaustive times were located within the generally recommended durations of 2-15 min. Ten triathletes (mean ± SD age: 31.0 ± 5.7 years; height: 1.81 ± 0.05 m; body mass: 76.5 ± 6.8 kg) performed two randomly assigned field tests to determine critical speed (CS) and the total distance covered above CS (D́). CS and D́ were obtained using two different protocols comprising three TT that were interspersed by 60 min passive rest. The TTs were 12, 7, and 3 min in Protocol I and 10, 5, and 2 min in Protocol II. A linear relationship of speed vs. the inverse of time (s = D́ × 1/t + CS) was used to determine parameter estimates. Significant differences were found for CS (p = 0.026), but not for D́ (p = 0.123). The effect size for CS (d = 0.305) was considered small, while that for D́ was considered moderate (d = 0.742). CS was significantly correlated between protocols (r = 0.934; p < 0.001), however, no correlation was found for D́ (r = 0.053; p = 0.884). The 95% limits of agreement were ±0.28m s-1 and ±73.9 m for CS and D́, respectively. These findings demonstrate that the choice of exhaustive times within commonly accepted durations results in different estimates of CS and D́, and thus protocols cannot be used interchangeably. The use of a consistent protocol is therefore recommended, when investigating or monitoring the speed-duration relationship estimates in well-trained athletes.

Reliability of the parameters of the power-duration relationship using maximal effort time-trials under laboratory conditions.

The purpose of this study was to assess the reliability of critical power (CP) and the total amount of work accomplished above CP (W´) across repeated tests using ecologically valid maximal effort time-trials (TT) under laboratory conditions. After an initial incremental exercise test, ten well-trained male triathletes (age: 28.5 ± 4.7 years; body mass: 73.3 ± 7.9 kg; height: 1.80 ± 0.07 m; maximal aerobic power [MAP]: 329 ± 41 W) performed three testing sessions (Familiarization, Test I and Test II) each comprising three TT (12, 7, and 3 min with a passive recovery of 60 min between trials). CP and W´ were determined using a linear regression of power vs. the inverse of time (1/t) (P = W´ ∙ 1/t + CP). A repeated-measures ANOVA was used to detect differences in CP and W´ and reliability was assessed using the intra-class correlation coefficient (ICC) and the coefficient of variation (CoV). CP and W´ values were not significantly different between repeated tests (P = 0.171 and P = 0.078 for CP and W´, respectively). The ICC between Familiarization and Test I was r = 0.86 (CP) and r = 0.58 (W´) and between Tests I and II it was r = 0.94 (CP) and r = 0.95 (W´). The CoV notably decreased from 4.1% to 2.6% and from 25.3% to 8.2% for CP and W´, respectively. Despite the non-significant differences for both parameter estimates between Familiarization, Test I, and Test II, ICC and CoV values improved notably after the familiarization trial. Our novel findings indicate that for both, CP and W´ a familiarization trial increased reliability. It is therefore advisable to familiarize well-trained athletes when determining the power-duration relationship using TT under laboratory conditions.

Iso-duration Determination of D' and CS under Laboratory and Field Conditions.

Whilst Critical Speed (CS) has been successfully translated from the laboratory into the field, this translation is still outstanding for the related maximum running distance (D'). Using iso-duration exhaustive laboratory and field runs, this study investigated the potential interchangeable use of both parameters, D' and CS. After an incremental exercise test, 10 male participants (age: 24.9±2.1 yrs; height: 180.8±5.8 cm; body mass: 75.3±8.6 kg; V̇ ˙VO2peak 52.9±3.1 mL∙min-1∙kg-1) performed 3 time-to-exhaustion runs on a treadmill followed by 3 exhaustive time-trial runs on a-400 m athletics outdoor track. Field time-trial durations were matched to their respective laboratory time-to-exhaustion runs. D' and CS were calculated using the inverse-time model (speed=D'/t+CS). Laboratory and field values of D' and CS were not significantly different (221±7 m vs. 225±72 m; P=0.73 and 3.75±0.36 m∙s-1 vs. 3.77±0.35 m∙s-1, P=0.68), and they were significantly correlated (r=0.86 and 0.94). The 95% LoA were ±75.5 m and ±0.24 m∙s-1 for D' and CS, respectively. Applying iso-durations provides non-significant differences for D' and CS and a significant correlation between conditions. This novel translation method can consequently be recommended to coaches and practitioners, however a questionable level of agreement indicates to use D' with caution.

Validity of Treadmill-Derived Critical Speed on Predicting 5000-Meter Track-Running Performance.

Nimmerichter, A, Novak, N, Triska, C, Prinz, B, and Breese, BC. Validity of treadmill-derived critical speed on predicting 5,000-meter track-running performance. J Strength Cond Res 31(3): 706-714, 2017-To evaluate 3 models of critical speed (CS) for the prediction of 5,000-m running performance, 16 trained athletes completed an incremental test on a treadmill to determine maximal aerobic speed (MAS) and 3 randomly ordered runs to exhaustion at the [INCREMENT]70% intensity, at 110% and 98% of MAS. Critical speed and the distance covered above CS (D') were calculated using the hyperbolic speed-time (HYP), the linear distance-time (LIN), and the linear speed inverse-time model (INV). Five thousand meter performance was determined on a 400-m running track. Individual predictions of 5,000-m running time (t = [5,000-D']/CS) and speed (s = D'/t + CS) were calculated across the 3 models in addition to multiple regression analyses. Prediction accuracy was assessed with the standard error of estimate (SEE) from linear regression analysis and the mean difference expressed in units of measurement and coefficient of variation (%). Five thousand meter running performance (speed: 4.29 ± 0.39 m·s; time: 1,176 ± 117 seconds) was significantly better than the predictions from all 3 models (p < 0.0001). The mean difference was 65-105 seconds (5.7-9.4%) for time and -0.22 to -0.34 m·s (-5.0 to -7.5%) for speed. Predictions from multiple regression analyses with CS and D' as predictor variables were not significantly different from actual running performance (-1.0 to 1.1%). The SEE across all models and predictions was approximately 65 seconds or 0.20 m·s and is therefore considered as moderate. The results of this study have shown the importance of aerobic and anaerobic energy system contribution to predict 5,000-m running performance. Using estimates of CS and D' is valuable for predicting performance over race distances of 5,000 m.