Heart rate performance curve during incremental cycle ergometer exercise in healthy young male subjects

Biomechanical, physiological and anthropometrical predictors of performance in recreational runners

Background

The maximal running speed (VMAX) determined on a graded treadmill test is well-recognized as a running performance predictor. However, few studies have assessed the variables that predict VMAX in recreationally active runners.

Methods

We used a mathematical procedure combining Fick's law and metabolic cost analysis to verify the relation between (1) VMAX versus anthropometric and physiological determinants of running performance and, (2) theoretical metabolic cost versus running biomechanical parameters. Linear multiple regression and bivariate correlation were applied. We aimed to verify the biomechanical, physiological, and anthropometrical determinants of VMAX in recreationally active runners. Fifteen recreationally active runners participated in this observational study. A Conconi and a stead-steady running test were applied using a heart rate monitor and a simple video camera to register the physiological and mechanical variables, respectively.

Results

Statistical analysis revealed that the speed at the second ventilatory threshold, theoretical metabolic cost, and fat-mass percentage confidently estimated the individual running performance as follows: VMAX = 58.632 + (-0.183 * fat percentage) + (-0.507 * heart rate percentage at second ventilatory threshold) + (7.959 * theoretical metabolic cost) (R2 = 0.62, p = 0.011, RMSE = 1.50 km.h-1). Likewise, the theoretical metabolic cost was significantly explained (R2 = 0.91, p = 0.004, RMSE = 0.013 a.u.) by the running spatiotemporal and elastic-related parameters (contact and aerial times, stride length and frequency, and vertical oscillation) as follows: theoretical metabolic cost = 10.421 + (4.282 * contact time) + (-3.795 * aerial time) + (-2.422 * stride length) + (-1.711 * stride frequency) + (0.107 * vertical oscillation).

Conclusion

Critical determinants of elastic mechanism, such as maximal vertical force and vertical and leg stiffness were unrelated to the metabolic economy. VMAX, a valuable marker of running performance, and its physiological and biomechanical determinants can be effectively evaluated using a heart rate monitor, treadmill, and a digital camera, which can be used in the design of training programs to recreationally active runners.

Physical workload and cardiopulmonary parameters in relation to individual capacity of bulk waste workers - a cross-sectional field-study

PURPOSE

Waste collection is considered particularly heavy work, although no previous study has yet investigated the strain of bulk waste collection. The aim of this study is to determine the workload of bulk waste workers in practice.

METHOD

We conducted a cross-sectional field-study. Fourteen male volunteers from the bulk waste collection of the municipal sanitation department in Hamburg, Germany, were included. Performance was determined by cardiopulmonary exercise testing under laboratory conditions. During the shift, each worker was accompanied by a researcher, and heart rate (HR) was recorded under field conditions using an HR watch with a belt system. We examined mean HR, relative heart rate (RHR), relative aerobic strain (RAS), calculated oxygen uptake ([Formula: see text])  and individual ventilatory threshold 1 (VT1) as parameters of workload during their daily work.

RESULTS

During the shift, HR was scaled: 102 bpm (SD 10.2), RHR: 36.9%, [Formula: see text]: 1267 ml/min (SD 161), RAS: 49.4% (SD 9.3), and [Formula: see text] in relation to VT1: 75% (SD 18.5). There was no significant difference between oxygen consumption during the main task of lifting and carrying bulky waste and the individual [Formula: see text] at VT1.

CONCLUSION

Although the burden of the main task of lifting and carrying bulky waste is very high (at VT1 for more than 3 h), interruptions from other tasks or formal breaks spread the burden over the entire shift. The total workload exceeded most recommendations in the literature across the different work periods. However, the total burden remains below VT1, the only parameter that takes individual endurance performance into account. We recommend again VT1 as an individual upper limit for prolonged occupational work.

Accelerometer-Derived Intensity Thresholds Are Equivalent to Standard Ventilatory Thresholds in Incremental Running Exercise

Accelerometer cut-points are commonly used to prescribe the amount of physical activity, but this approach includes no individual performance measures. As running kinetics change with intensity, acceleration measurements may provide more individual information. Therefore, the aim was to determine two intensity thresholds from accelerometer measures. A total of 33 participants performed a maximal incremental running test with spirometric and acceleration (Axivity AX3) measures at the left and right tibia. Ventilatory equivalents (VE/VO2, VE/VCO2) were used to determine a first and second ventilatory threshold (VT1/VT2). A first and second accelerometer threshold (ACT1/ACT2) were determined within the same regions of interest from vector magnitude (|v| = √(ax2 + ay2 + az2). Accelerometer data from the tibia presented a three-phase increase with increasing speed. Speed at VT1/VT2 (7.82 ± 0.39/10.91 ± 0.87 km/h) was slightly but significantly lower compared to the speed at ACT1/ACT2 from the left (7.71 ± 0.35/10.62 ± 0.72 km/h) and right leg (7.79 ± 0.33/10.74 ± 0.77 km/h). Correlation analysis revealed a strong relationship between speed at thresholds determined from spriometric data or accelerations (r = 0.98; p < 0.001). It is therefore possible to determine accelerometer thresholds from tibia placement during a maximal incremental running test comparable to standard ventilatory thresholds.

Maximal oxygen uptake prediction from submaximal bicycle ergometry using a differential model

The maximal oxygen uptake (VO₂max) estimation has been a subject of research for many years. Cardiorespiratory measurements during incremental tests until exhaustion are considered the golden yard stick to assess VO₂max. However, precise VO₂max determination based on submaximal tests is attractive for athlete as well for clinical populations. Here, we propose and verify such a method based on experimental data. Using a recently developed model of heart rate (HR) and VO₂ kinetics in graded exercise tests, we applied a protocol, which is terminated at 80% of the estimated maximal HR during ergometer cycling. In our approach, initially, formula for maximal HR is selected by retrospective study of a reference population (17 males, 23.5 ± 2.0 years, BMI: 23.9 ± 3.2 kg/m²). Next, the subjects for experimental group were invited (nine subjects of both sexes: 25.1 ± 2.1 years, BMI 23.2 ± 2.2 kg/m²). After calculation of maximal HR using cardiorespiratory recordings from the submaximal test, VO₂max is predicted. Finally, we compared the prediction with the values from the maximal exercise test. The differences were quantified by relative errors, which vary from 1.2% up to 13.4%. Some future improvements for the procedure of VO₂max prediction are discussed. The experimental protocol may be useful for application in rehabilitation assessment and in certain training monitoring settings, since physical exertion is not a prerequisite and the approach provides an acceptable VO₂max estimation accuracy.

Pattern of the heart rate performance curve in maximal graded treadmill running from 1100 healthy 18-65 Years old men and women: the 4HAIE study

Introduction: The heart rate performance curve (HRPC) in maximal incremental cycle ergometer exercise demonstrated three different patterns such as downward, linear or inverse versions. The downward pattern was found to be the most common and therefore termed regular. These patterns were shown to differently influence exercise prescription, but no data are available for running. This study investigated the deflection of the HRPC in maximal graded treadmill tests (GXT) of the 4HAIE study. Methods: Additional to maximal values, the first and second ventilatory thresholds as well as the degree and the direction of the HRPC deflection (k_HR) were determined from 1,100 individuals (489 women) GXTs. HRPC deflection was categorized as downward (k_HR < -0.1), linear (-0.1 ≤ k_HR ≤ 0.1) or inverse (k_HR > 0.1) curves. Four (even split) age- and two (median split) performance-groups were used to investigate the effects of age and performance on the distribution of regular (= downward deflection) and non-regular (= linear or inverse course) HR curves for male and female subjects. Results: Men (age: 36.8 ± 11.9 years, BMI: 25.0 ± 3.3 kg m^-2, VO_2max: 46.4 ± 9.4 mL min^-1. kg^-1) and women (age: 36.2 ± 11.9 years, BMI: 23.3 ± 3.7 kg m^-2, VO_2max: 37.4 ± 7.8 mL min^-1. kg^-1) presented 556/449 (91/92%) downward deflecting, 10/8 (2/2%) linear and 45/32 (7/6%) inverse HRPC´s. Chi-squared analysis revealed a significantly higher number of non-regular HRPC´s in the low-performance group and with increasing age. Binary logistic regression revealed that the odds ratio (OR) to show a non-regular HRPC is significantly affected by maximum performance (OR = 0.840, 95% CI = 0.754-0.936, p = 0.002) and age (OR = 1.042, 95% CI = 1.020-1.064, p < 0.001) but not sex. Discussion: As in cycle ergometer exercise, three different patterns for the HRPC were identified from the maximal graded treadmill exercise with the highest frequency of regular downward deflecting curves. Older subjects and subjects with a lower performance level had a higher probability to show a non-regular linear or inverted curve which needs to be considered for exercise prescription.

VO2max and Velocity at VO2max Play a Role in Ultradistance Trail-Running Performance

PURPOSE

Previous research has shown that maximal oxygen uptake (VO2max) significantly influences performance in trail-running races up to 120 km but not beyond. Similarly, the influence of running economy on performance in ultratrail remains unclear. The aim of our study was, therefore, to determine the physiological predictors of performance in a 166-km trail-running race.

METHODS

Thirty-three experienced trail runners visited the laboratory 4 to 8 weeks before the race to undergo physiological testing including an incremental treadmill test and strength assessments. Correlations and regression analyses were used to determine the physiological variables related to performance.

RESULTS

Average finishing time was 37:33 (5:52) hours. Performance correlated significantly with VO2max (r = -.724, P < .001), velocity at VO2max (r = -.813, P < .001), lactate turn point expressed as percentage of VO2max (r = -.510, P = .018), cost of running (r = -.560, P = .008), and body fat percentage (r = .527, P = .012) but was not related to isometric strength. Regression analysis showed that velocity at VO2max predicted 65% of the variability in performance (P < .001), while a model combining VO2max and cost of running combined predicted 62% of the variability (P = .008).

CONCLUSION

This is the first study to show that VO2max and velocity at VO2max are significant predictors of performance in a 166-km trail-running race. This suggests that ultratrail runners should focus on the development of these 2 qualities to optimize their race performance.

Glucose and Fructose Supplementation and Their Acute Effects on Electrocardiographic Time Intervals during Anaerobic Cycling Exercise in Healthy Individuals: A Secondary Outcome Analysis of a Double-Blind Randomized Crossover-Controlled Trial

The impact of glucose and fructose supplementation on acute cardiac effects during cardiopulmonary exercise testing (CPET) is a topic that is rarely investigated. The aim of the presented secondary outcome analysis of a double-blind, randomized crossover-controlled trial was to investigate the impact of glucose (Glu), fructose (Fru), glucose and fructose (GluFru), and sucralose on electrocardiogram (ECG), heart rate variability (HRV), premature ventricular complexes (PVCs), and heart rate turn points (HRTP) during CPET. Fourteen healthy individuals (age 25.4 ± 2.5 years, body mass index (BMI) 23.7 ± 1.7 kg/m2, body mass (BM) of 76.3 ± 12.3 kg) participated in this study, of which 12 were included for analysis. Participants received 1 g/kg BM of Glu, 1 g/kg BM of Fru, 0.5 g/kg BM of GluFru (each), and 0.2 g sucralose dissolved in 300 mL 30 min prior to each exercise session. No relevant clinical pathology or significant inter-individual differences between our participants could be revealed for baseline ECG parameters, such as heart rate (HR) (mean HR 70 ± 16 bpm), PQ interval (146 ± 20 ms), QRS interval (87 ± 16 ms) and the QT (405 ± 39 ms), and QTc interval (431 ± 15 ms). We found preserved cardiac autonomic function by analyzing the acute effects of different Glu, Fru, GluFru, or sucralose supplementation on cardiac autonomic function by Schellong-1 testing. SDNN and RMSSD revealed normal sympathetic and parasympathetic activities displaying a balanced system of cardiac autonomic regulation across our participating subjects with no impact on the metabolism. During CPET performance analyses, HRV values did not indicate significant changes between the ingested drinks within the different time points. Comparing the HRTP of the CPET with endurance testing by variable metabolic conditions, no significant differences were found between the HRTP of the CPET data (170 ± 12 bpm), Glu (171 ± 10 bpm), Fru (171 ± 9 bpm), GluFru (172 ± 9 bpm), and sucralose (170 ± 8 bpm) (p = 0.83). Additionally, the obtained time to reach HRTP did not significantly differ between Glu (202 ± 75 s), Fru (190 ± 88 s), GluFru (210 ± 89 s), and sucralose (190 ± 34 s) (p = 0.59). The significance of this study lies in evaluating the varying metabolic conditions on cardiac autonomic modulation in young healthy individuals. In contrast, our participants showed comparable cardiac autonomic responses determined by ECG and CPET.

Effects of Different Durations at Fixed Intensity Exercise on Internal Load and Recovery-A Feasibility Pilot Study on Duration as an Independent Variable for Exercise Prescription

Duration is a rarely investigated marker of exercise prescription. The aim of this study was to test the feasibility of the methodological approach, assessing effects of different duration constant-load exercise (CLE) on physiological responses (internal load) and recovery kinetics. Seven subjects performed an incremental exercise (IE) test, one maximal duration CLE at 77.6 ± 4.8% V˙O2max, and CLE's at 20%, 40%, and 70% of maximum duration. Heart rate (HR), blood lactate (La), and glucose (Glu) concentrations were measured. Before, 4, 24, and 48 h after CLE's, submaximal IE tests were performed. HR variability (HRV) was assessed in orthostatic tests (OT). Rating of perceived exertion (RPE) was obtained during all tests. CLE's were performed at 182 ± 27 W. HR_peak, La_peak, V˙Epeak, and RPE_peak were significantly higher in CLE's with longer duration. No significant differences were found between CLE's for recovery kinetics for HR, La, and Glu in the submaximal IE and for HRV or OT. Despite no significant differences, recovery kinetics were found as expected, indicating the feasibility of the applied methods. Maximum tests and recovery tests closer to CLE's termination are suggested to better display recovery kinetics. These findings are a first step to prescription of exercise by both intensity and duration on an individual basis.

miRNAs as markers for the development of individualized training regimens: A pilot study

Small, non‐coding RNAs (microRNAs) have been shown to regulate gene expression in response to exercise in various tissues and organs, thus possibly coordinating their adaptive response. Thus, it is likely that differential microRNA expression might be one of the factors that are responsible for different training responses of different individuals. Consequently, determining microRNA patterns might be a promising approach toward the development of individualized training strategies. However, little is known on (1) microRNA patterns and their regulation by different exercise regimens and (2) possible correlations between these patterns and individual training adaptation. Here, we present microarray data on skeletal muscle microRNA patterns in six young, female subjects before and after six weeks of either moderate‐intensity continuous or high‐intensity interval training on a bicycle ergometer. Our data show that n = 36 different microRNA species were regulated more than twofold in this cohort (n = 28 upregulated and n = 8 downregulated). In addition, we correlated baseline microRNA patterns with individual changes in VO₂max and identified some specific microRNAs that might be promising candidates for further testing and evaluation in the future, which might eventually lead to the establishment of microRNA marker panels that will allow individual recommendations for specific exercise regimens.

Electromyographic and Systemic Physiological Thresholds in Single-Joint Elbow Flexion Movements

PURPOSE

Reported relationships between electromyographic (EMG) thresholds and systemic thresholds based on lactate, ventilation, or heart rate are contradictory. This might be related to the complexity of the investigated whole-body movements involving many muscles with different activation patterns. Therefore, the aim of the study was to investigate these relationships during an incremental single-joint exercise.

METHODS

Eighteen male subjects (29.7 [4.4] y) performed single-arm elbow flexions on a biceps curl machine with loads increasing every minute until exhaustion. EMG signals of the main elbow flexors (short and long head of the biceps brachii, flexor carpi radialis, and brachioradialis) as well as gas exchange variables, blood lactate concentration, and heart rate were measured, and 2 turn points based on a 3-phase model of metabolism were determined for each variable.

RESULTS

The first and second turn points for EMG were determined at 32.0% to 33.1% and 64.4% to 66.5% of maximal achieved performance (maximum weight), respectively. Systemic turn points were determined at 33.3% to 34.4% and 65.9% to 66.7% of maximum weight and were not significantly different from EMG turn points. Furthermore, systemic and EMG turn points showed a strong or very strong relationship at the first (ρ = .54-.93, P < .05) and second turn point (ρ = .76-.93, P < .01).

CONCLUSIONS

A close relationship between EMG and systemic turn points could be confirmed for the applied movement of a small muscle group. The determination of local single muscle thresholds using EMG provides additional muscle-specific information about performance-limiting properties of muscles involved in endurance-type incremental exercise.

Pattern of the Heart Rate Performance Curve in Subjects with Beta-Blocker Treatment and Healthy Controls

(1): Heart rate performance curve (HRPC) in incremental exercise was shown to be not uniform, causing false intensity estimation applying percentages of maximal heart rate (HR_max). HRPC variations are mediated by β-adrenergic receptor sensitivity. The aim was to study age and sex dependent differences in HRPC patterns in adults with β-blocker treatment (BB) and healthy controls (C). (2): A total of 535 (102 female) BB individuals were matched 1:1 for age and sex (male 59 ± 11 yrs, female 61 ± 11 yrs) in C. From the maximum incremental cycle ergometer exercise a first and second heart rate (HR) threshold (Th1 and Th2) was determined. Based on the degree of the deflection (kHR), HRPCs were categorized as regular (downward deflection (kHR > 0.1)) and non-regular (upward deflection (kHR < 0.1), linear time course). (3): Logistic regression analysis revealed a higher odds ratio to present a non-regular curve in BB compared to C (females showed three times higher odds). The odds for non-regular HRPC in BB versus C decreased with older age (OR interaction = 0.97, CI = 0.94-0.99). Maximal and submaximal performance and HR variables were significantly lower in BB (p < 0.05). %HR_max was significantly lower in BB versus C at Th2 (male: 77.2 ± 7.3% vs. 80.8 ± 5.0%; female: 79.2 ± 5.1% vs. 84.0 ± 4.3%). %P_max at Th2 was similar in BB and C. (4): The HRPC pattern in incremental cycle ergometer exercise is different in individuals receiving β-blocker treatment compared to healthy individuals. The effects were also dependent on age and sex. Relative HR values at Th2 varied substantially depending on treatment. Thus, the percentage of Pmax seems to be a stable and independent indicator for exercise intensity prescription.

Individual cardiovascular responsiveness to work-matched exercise within the moderate- and severe-intensity domains

Purpose

We investigated the cardiovascular individual response to 6 weeks (3×/week) of work-matched within the severe-intensity domain (high-intensity interval training, HIIT) or moderate-intensity domain (moderate-intensity continuous training, MICT). In addition, we analyzed the cardiovascular factors at baseline underlying the response variability.

Methods

42 healthy sedentary participants were randomly assigned to HIIT or MICT. We applied the region of practical equivalence-method for identifying the levels of responders to the maximal oxygen uptake (V̇O_2max) response. For investigating the influence of cardiovascular markers, we trained a Bayesian machine learning model on cardiovascular markers.

Results

Despite that HIIT and MICT induced significant increases in V̇O_2max, HIIT had greater improvements than MICT (p < 0.001). Greater variability was observed in MICT, with approximately 50% classified as “non-responder” and “undecided”. 20 “responders”, one “undecided” and no “non-responders” were observed in HIIT. The variability in the ∆V̇O_2max was associated with initial cardiorespiratory fitness, arterial stiffness, and left-ventricular (LV) mass and LV end-diastolic diameter in HIIT; whereas, microvascular responsiveness and right-ventricular (RV) excursion velocity showed a significant association in MICT.

Conclusion

Our findings highlight the critical influence of exercise-intensity domains and biological variability on the individual V̇O_2max response. The incidence of “non-responders” in MICT was one third of the group; whereas, no “non-responders” were observed in HIIT. The incidence of “responders” was 11 out of 21 participants in MICT, and 20 out of 21 participants in HIIT. The response in HIIT showed associations with baseline fitness, arterial stiffness, and LV-morphology; whereas, it was associated with RV systolic function in MICT.

Agreement between heart rate deflection point and maximal lactate steady state in young adults with different body masses

We examined the agreement between heart rate deflection point (HRDP) variables with maximal lactate steady state (MLSS) in a sample of young males categorized to different body mass statuses using body mass index (BMI) cut-off points. One hundred and eighteen young males (19.9 ± 4.4 years) underwent a standard running incremental protocol with individualized speed increment between 0.3 and 1.0 km/h for HRDP determination. HRDP was determined using the modified Dmax method called S.Dmax. MLSS was determined using 2-5 series of constant-speed treadmill runs. Heart rate (HR) and blood lactate concentration (La) were measured in all tests. MLSS was defined as the maximal running speed yielding a La increase of less than 1 mmol/L during the last 20 min. Good agreement was observed between HRDP and MLSS for HR for all participants (±1.96; 95% CI = -11.5 to +9.2 b/min, ICC = 0.88; P < 0.001). Good agreement was observed between HRDP and MLSS for speed for all participants (±1.96; 95% CI = -0.40 to +0.42 km/h, ICC = 0.98; P < 0.001). The same findings were observed when participants were categorized in different body mass groups. In conclusion, HRDP can be used as a simple, non-invasive and time-efficient method to objectively determine submaximal aerobic performance in nonathletic young adult men with varying body mass status, according to the chosen standards for HRDP determination.

The complex relationship between effort and heart rate: a hint from dynamic analysis

OBJECTIVE

Dynamic analysis can be used to study the changes of self-regulated biological processes driven by external stimuli. Recently, the changes of heart rate during effort tests has successfully been adjusted using a simple first-order differential equation model driven by body power expenditure. Although this approach produces valid estimates and yields pertinent indices for the analysis of such measurements, it suffers from an inability to model the saturation of the heart-rate increase at high power expenditures and the change of heart-rate equilibrium following effort.

APPROACH

We propose a new analysis allowing the estimation of changes of the heart rate in response to effort (gain) as a function of the power expenditure value.

MAIN RESULTS

When applied to the measured heart rates of 30 amateur athletes performing a maximum graded-effort treadmill test, the proposed model was able to predict 99% of the heart rate change measured during exercise. The estimated gains decreased with a power increase above the first ventilatory threshold. This trend was stronger above the second ventilatory threshold and was strongly correlated with the maximum oxygen consumption.

SIGNIFICANCE

The proposed approach yields a highly precise model of heart rate dynamics during variable effort that reflects the changes of metabolic energy systems at play during exercise.

The First Lactate Threshold Is a Limit for Heavy Occupational Work

Long-term heavy physical work often leads to early retirement and disability pension due to chronic overload, with a need to define upper limits. The aim of this study was to evaluate the value of the first lactate threshold (LTP₁) as a physiological marker for heavy occupational work. A total of 188 male and 52 female workers performed an incremental cycle ergometer test to determine maximal exercise performance and the first and second lactate (LTP₁; LTP₂) and ventilatory thresholds (VT₁; VT₂). Heart rate (HR) recordings were obtained during one eight-hour shift (HR_8h) and oxygen uptake was measured during 20 minutes of a representative work phase. Energy expenditure (EE) was calculated from gas-exchange measures. Maximal power output (P_max), maximal oxygen consumption (VO_{2 max}) and power output at LTP₁ and LTP₂ were significantly different between male and female workers. HR_8h was not significantly different between male and female workers. A significant relationship was found between P_max and power output at LTP₁. HR_8h as a percentage of maximum HR significantly declined with increasing performance (P_max:r = −0.56; p < 0.01; P_LTP1:r = −0.49; p < 0.01). Despite different cardio-respiratory fitness-levels; 95.4% of all workers performed their usual work below LTP₁. It is therefore suggested that LTP₁ represents the upper limit for sustained heavy occupational work; which supports its use to determine work capability and assessing the limits of heavy occupational work.

Validity of dynamical analysis to characterize heart rate and oxygen consumption during effort tests

Performance is usually assessed by simple indices stemming from cardiac and respiratory data measured during graded exercise test. The goal of this study is to characterize the indices produced by a dynamical analysis of HR and VO₂ for different effort test protocols, and to estimate the construct validity of these new dynamical indices by testing their links with their standard counterparts. Therefore, two groups of 32 and 14 athletes from two different cohorts performed two different graded exercise testing before and after a period of training or deconditioning. Heart rate (HR) and oxygen consumption (VO₂) were measured. The new dynamical indices were the value without effort, the characteristic time and the amplitude (gain) of the HR and VO₂ response to the effort. The gain of HR was moderately to strongly associated with other performance indices, while the gain for VO₂ increased with training and decreased with deconditioning with an effect size slightly higher than VO₂ max. Dynamical analysis performed on the first 2/3 of the effort tests showed similar patterns than the analysis of the entire effort tests, which could be useful to assess individuals who cannot perform full effort tests. In conclusion, the dynamical analysis of HR and VO₂ obtained during effort test, especially through the estimation of the gain, provides a good characterization of physical performance, robust to less stringent effort test conditions.

Intensity Thresholds and Maximal Lactate Steady State in Small Muscle Group Exercise

The aim of our study is to determine the first (LTP₁) and the second (LTP₂) lactate turn points during an incremental bicep curl test and to verify these turn points by ventilatory turn points (VT₁ and VT₂) and constant-load exercise tests. Twelve subjects performed a one-arm incremental bicep curl exercise (IET) after a one repetition maximum (1RM) test to calculate the step rate for the incremental exercise (1RM/45). Workload was increased every min at a rate of 30 reps/min until maximum. To verify LTPs, VT₁ and VT₂ were determined from spirometric data, and 30 min constant-load tests (CL) were performed at 5% P_max below and above turn points. Peak load in IET was 5.3 ± 0.9 kg (La_max: 2.20 ± 0.40 mmol·L⁻¹; HR_max: 135 ± 15 b·min⁻¹; VO_2max: 1.15 ± 0.30 L·min⁻¹). LTP₁ was detected at 1.9 ± 0.6 kg (La: 0.86 ± 0.36 mmol·L⁻¹; HR 90 ± 13 b·min⁻¹; VO₂: 0.50 ± 0.05 L·min⁻¹) and LTP₂ at 3.8 ± 0.7 kg (La: 1.38 ± 0.37 mmol·L⁻¹; 106 ± 10 b·min⁻¹; VO₂: 0.62 ± 0.11 L·min⁻¹). Constant-load tests showed a lactate steady-state in all tests except above LTP₂, with early termination after 16.5 ± 9.1 min. LTP₁ and LTP₂ could be determined in IET, which were not significantly different from VT₁/VT₂. Constant-load exercise validated the three-phase concept, and a steady-state was found at resting values below VT₁ and in all other tests except above LTP₂. It is suggested that the three-phase model is also applicable to small muscle group exercise.

Heart Rate Performance Curve Is Dependent on Age, Sex, and Performance

Introduction: The Heart Rate Performance Curve (HRPC) is neither linear nor uniform and related to ß1-adrenoceptor sensitivity. As aging and exercise influence ß1-adrenoceptors we suggested age, sex and performance effects on the HRPC. Aim of the study was to examine the effects of aging on the deflection of the HRPC in maximal incremental cycle ergometer exercise (CE) in a large cohort of healthy subjects.

Methods: Heart rate (HR) data of 2,980 men (51 ± 15 years) and 1,944 women (52 ± 14 years) were classified into age groups (≤20 up to >80 years). We analyzed age and performance (P_low 25%-quartile and P_high 75%-quartile of age predicted power) effects on HR_max and on the degree (k) and the type (regular downward deflection k > 0.1, linear −0.1 ≤ k ≤ 0.1 and atypical upward deflection k < −0.1) of the HRPC.

Results:k-values decreased significantly with age in men and women and were significantly higher in women. Atypical HRPC's increased by a linear trend from ≤20 to 70 years (m) respectively 80 years (w) from 10 to 43% (m) and 9 to 30% (w). HR_max of all age groups was lower in P_low and overall number of atypical HRPC's was 21% (m) and 16% (w) higher compared to P_high.

Conclusion: Aging increased the number of atypical HRPC's with upward deflection in CE tests, which influences exercise intensity prescription especially when using fixed percentages of HR_max. Changes in HRPC's were affected by sex and performance, where women generally and subjects with higher performance presented less atypical HRPC's even at older age.

The iReAct study - A biopsychosocial analysis of the individual response to physical activity

Background

Physical activity is a substantial promoter for health and well-being. Yet, while an increasing number of studies shows that the responsiveness to physical activity is highly individual, most studies focus this issue from only one perspective and neglect other contributing aspects. In reference to a biopsychosocial framework, the goal of our study is to examine how physically inactive individuals respond to two distinct standardized endurance trainings on various levels. Based on an assessment of activity- and health-related biographical experiences across the life course, our mixed-method study analyzes the responsiveness to physical activity in the form of a transdisciplinary approach, considering physiological, epigenetic, motivational, affective, and body image-related aspects.

Methods

Participants are randomly assigned to two different training programs (High Intensity Interval Training vs. Moderate Intensity Continuous Training) for six weeks. After this first training period, participants switch training modes according to a two-period sequential-training-intervention (STI) design and train for another six weeks. In order to analyse baseline characteristics as well as acute and adaptive biopsychosocial responses, three extensive mixed-methods diagnostic blocks take place at the beginning (t₀) of the study and after the first (t₁) and the second (t₂) training period resulting in a net follow-up time of 15 weeks. The study is divided into five modules in order to cover a wide array of perspectives.

Discussion

The study's transdisciplinary mixed-method design allows to interlace a multitude of subjective and objective data and therefore to draw an integrated picture of the biopsychosocial efficacy of two distinct physical activity programs. The results of our study can be expected to contribute to the development and design of individualised training programs for the promotion of physical activity.

Trial registration

The study was retrospectively registered in the German Clinical Trials Register on 12 June 2019 (DRKS00017446).

Exercise-based cardiac rehabilitation is associated with a normalization of the heart rate performance curve deflection

The heart rate (HR) rises with increased power output, whereby in most healthy individuals, the slope of HR levels off with higher intensity. This corresponds to a downward deflection of the heart rate performance curve (HRPC). Conversely, in patients after myocardial infarction, an upward HRPC deflection is frequently observed that is especially pronounced in patients with compromised left ventricular ejection fraction. To investigate whether regular endurance training during cardiac rehabilitation might normalize HRPC, data of 128 male patients were analyzed. All patients performed three exercise tests: at baseline, after 6 weeks, and after 1 year. Ninety‐six patients exercised regularly according to guidelines for 1 year (training group, TG), and 32 stopped after 6 weeks (control group, CG). Similarly, upward‐deflected HRPCs were observed at baseline and after 6 weeks in both groups. After 1 year, TG patients had less upward‐deflected HRPCs compared with CG ones, corresponding to a partial normalization. Greater changes in HRPC deflection were associated with larger improvements in cardiorespiratory fitness. Our results might indicate improved myocardial function due to long‐term rehabilitation. Further, HRPC alterations over time should be considered when prescribing exercise intensities using a target HR, as deflection flattening might render the intensity of corresponding exercise insufficient.

Heart rate dynamics during cardio-pulmonary exercise testing are associated with glycemic control in individuals with type 1 diabetes

INTRODUCTION

This study investigated the degree and direction (kHR) of the heart rate to performance curve (HRPC) during cardio-pulmonary exercise (CPX) testing and explored the relationship with diabetes markers, anthropometry and exercise physiological markers in type 1 diabetes (T1DM).

MATERIAL AND METHODS

Sixty-four people with T1DM (13 females; age: 34 ± 8 years; HbA1c: 7.8 ± 1% (62 ± 13 mmol.mol-1) performed a CPX test until maximum exhaustion. kHR was calculated by a second-degree polynomial representation between post-warm up and maximum power output. Adjusted stepwise linear regression analysis was performed to investigate kHR and its associations. Receiver operating characteristic (ROC) curve was performed based on kHR for groups kHR < 0.20 vs. > 0.20 in relation to HbA1c.

RESULTS

We found significant relationships between kHR and HbA1c (β = -0.70, P < 0.0001), age (β = -0.23, P = 0.03) and duration of diabetes (β = 0.20, P = 0.04). Stepwise linear regression resulted in an overall adjusted R2 of 0.57 (R = 0.79, P < 0.0001). Our data revealed also significant associations between kHR and percentage of heart rate at heart rate turn point from maximum heart rate (β = 0.43, P < 0.0001) and maximum power output relativized to bodyweight (β = 0.44, P = 0.001) (overall adjusted R2 of 0.44 (R = 0.53, P < 0.0001)). ROC curve analysis based on kHR resulted in a HbA1c threshold of 7.9% (62 mmol.mol-1).

CONCLUSION

Our data demonstrate atypical HRPC during CPX testing that were mainly related to glycemic control in people with T1DM.

Different Heart Rate Patterns During Cardio-Pulmonary Exercise (CPX) Testing in Individuals With Type 1 Diabetes

To investigate the heart rate during cardio-pulmonary exercise (CPX) testing in individuals with type 1 diabetes (T1D) compared to healthy (CON) individuals. Fourteen people (seven individuals with T1D and seven CON individuals) performed a CPX test until volitional exhaustion to determine the first and second lactate turn points (LTP₁ and LTP₂), ventilatory thresholds (VT₁ and VT₂), and the heart rate turn point. For these thresholds cardio-respiratory variables and percentages of maximum heart rate, heart rate reserve, maximum oxygen uptake and oxygen uptake reserve, and maximum power output were compared between groups. Additionally, the degree and direction of the deflection of the heart rate to performance curve (k_HR) were compared between groups. Individuals with T1D had similar heart rate at LTP₁ (mean difference) -11, [(95% confidence interval) -27 to 4 b.min^-1], at VT₁ (-12, -8 to 33 b.min^-1) and at LTP₂ (-7, -13 to 26 b.min^-1), at VT₂ (-7, -13 to 28 b.min^-1), and at the heart rate turn point (-5, -14 to 24 b.min^-1) (p = 0.22). Heart rate expressed as percentage of maximum heart rate at LTP₁, VT₁, LTP₂, VT₂ and the heart rate turn point as well as expressed as percentages of heart rate reserve at LTP₂, VT₂ and the heart rate turn point was lower in individuals with T1D (p < 0.05). k_HR was lower in T1D compared to CON individuals (0.11 ± 0.25 vs. 0.51 ± 0.32, p = 0.02). Our findings demonstrate that there are clear differences in the heart rate response during CPX testing in individuals with T1D compared to CON individuals. We suggest using submaximal markers to prescribe exercise intensity in people with T1D, as the heart rate at thresholds is influenced by k_HR. Clinical Trial Identifier: NCT02075567 (https://clinicaltrials.gov/ct2/show/NCT02075567).

Intensity- and Duration-Based Options to Regulate Endurance Training

The regulation of endurance training is usually based on the prescription of exercise intensity. Exercise duration, another important variable of training load, is rarely prescribed by individual measures and mostly set from experience. As the specific exercise duration for any intensity plays a substantial role regarding the different kind of cellular stressors, degree, and kind of fatigue as well as training effects, concepts integrating the prescription of both intensity and duration within one model are needed. An according recent approach was the critical power concept which seems to have a physiological basis; however, the mathematical approach of this concept does not allow applying the three zones/two threshold model of metabolism and its different physiological consequences. Here we show the combination of exercise intensity and duration prescription on an individual basis applying the power/speed to distance/time relationship. The concept is based on both the differentiation of intensities by two lactate or gas exchange variables derived turn points, and on the relationship between power (or velocity) and duration (or distance). The turn points define three zones of intensities with distinct acute metabolic, hormonal, and cardio-respiratory responses for endurance exercise. A maximal duration exists for any single power or velocity such as described in the power-duration relationship. Using percentages of the maximal duration allows regulating fatigue, recovery time, and adaptation for any single endurance training session. Four domains of duration with respect to induced fatigue can be derived from maximal duration obtained by the power-duration curve. For any micro-cycle, target intensities and durations may be chosen on an individual basis. The model described here is the first conceptual framework of integrating physiologically defined intensities and fatigue related durations to optimize high-performance exercise training.

Poor glycaemic control is associated with reduced exercise performance and oxygen economy during cardio-pulmonary exercise testing in people with type 1 diabetes

BACKGROUND

To explore the impact of glycaemic control (HbA_1c) on functional capacity during cardio-pulmonary exercise testing in people with type 1 diabetes.

METHODS

Sixty-four individuals with type 1 diabetes (age: 34 ± 8 years; 13 females, HbA_1c: 7.8 ± 1% (62 ± 13 mmol/mol), duration of diabetes: 17 ± 9 years) performed a cardio-pulmonary cycle ergometer exercise test until volitional exhaustion. Stepwise linear regression was used to explore relationships between HbA_1c and cardio-respiratory data with p ≤ 0.05. Furthermore, participants were divided into quartiles based on HbA_1c levels and cardio-respiratory data were analysed by one-way ANOVA. Multiple regression analysis was performed to explore the relationships between changes in time to exhaustion and cardio-respiratory data. Data were adjusted for confounder.

RESULTS

HbA_1c was related to time to exhaustion and oxygen consumption at the power output elicited at the sub-maximal threshold of the heart rate turn point (r = 0.47, R² = 0.22, p = 0.03). Significant differences were found at time to exhaustion between QI vs. QIV and at oxygen consumption at the power output elicited at the heart rate turn point between QI vs. QII and QI vs. QIV (p < 0.05). Changes in oxygen uptake, power output and in oxygen consumption at the power output elicited at the heart rate turn point and at maximum power output explained 55% of the variance in time to exhaustion (r = 0.74, R² = 0.55, p < 0.01).

CONCLUSIONS

Poor glycaemic control is related to less economical use of oxygen at sub-maximal work rates and an earlier time to exhaustion during cardio-pulmonary exercise testing. However, exercise training could have the same potential to counteract the influence of poor glycaemic control on functional capacity. Trial registration NCT01704417. Date of registration: October 11, 2012.

Graded Exercise Testing Protocols for the Determination of VO2max: Historical Perspectives, Progress, and Future Considerations

Graded exercise testing (GXT) is the most widely used assessment to examine the dynamic relationship between exercise and integrated physiological systems. The information from GXT can be applied across the spectrum of sport performance, occupational safety screening, research, and clinical diagnostics. The suitability of GXT to determine a valid maximal oxygen consumption (VO₂max) has been under investigation for decades. Although a set of recommended criteria exists to verify attainment of VO₂max, the methods that originally established these criteria have been scrutinized. Many studies do not apply identical criteria or fail to consider individual variability in physiological responses. As an alternative to using traditional criteria, recent research efforts have been directed toward using a supramaximal verification protocol performed after a GXT to confirm attainment of VO₂max. Furthermore, the emergence of self-paced protocols has provided a simple, yet reliable approach to designing and administering GXT. In order to develop a standardized GXT protocol, additional research should further examine the utility of self-paced protocols used in conjunction with verification protocols to elicit and confirm attainment of VO₂max.

Determination of Anaerobic Threshold by Monitoring the O2 Pulse Changes in Endurance Cyclists

The purpose of this study was to determine the validity of anaerobic threshold (AnT)-equivalent to the second turn point for lactate (LTP2)-estimation using the O2 pulse changes in highly trained endurance cyclists who do not show heart rate deflection point (HRDP) during incremental testing. Sixteen endurance cyclists (age, 24.8 ± 4.7 years) and fifteen active men (age, 24.8 ± 3.7 years) performed an incremental cycling test to exhaustion. Pulmonary oxygen uptake (V[Combining Dot Above]O2) and other hemodynamic variables, heart rate, and blood lactate concentration were measured continuously throughout the test. O2 pulse anaerobic threshold (O2 pulse-AnT) was defined as the second turn point in O2 pulse-workload curve. LTP2 was considered as gold standard assessment of AnT and was applied to confirm the validity of O2 pulse-AnT. Intraclass correlation coefficients and the Bland-Altman method were used to determine the relationship and agreement between the O2 corresponding to LTP2 and O2 pulse-AnT, respectively. The active men and 68.7% of the endurance cyclists showed HRDP, whereas all subjects showed O2 pulse-AnT during incremental testing. In both groups, the values for V[Combining Dot Above]O2 corresponding to LTP2 were not significantly different from the V[Combining Dot Above]O2 at O2 pulse-AnT. The V[Combining Dot Above]O2 at LTP2 and O2 pulse-AnT were highly correlated (endurance cyclists: R = 0.68; standard error of estimate [SEE] = 3.74 ml·kg·min and active men: R = 0.58; SEE = 2.91 ml·kg·min) and Bland-Altman plot revealed the limit of agreement of O2 at LTP2 and O2 pulse-AnT differences between 5.1 and 8.6 ml·kg·min (95% CI). In summary, results of this study showed that the second turn point in the O2 pulse-workload curve occurs around LTP2. Therefore, using O2 pulse-AnT is recommended for the noninvasive determination of AnT in highly trained endurance cyclists who do not show HRDP during incremental exercise.

Using heart rate to predict energy expenditure in large domestic dogs

The aim of this study was to establish heart rate as a measure of energy expenditure in large active kennel dogs (28 ± 3 kg bw). Therefore, the heart rate (HR)-oxygen consumption (V˙O2) relationship was analysed in Foxhound-Boxer-Ingelheim-Labrador cross-breds (FBI dogs) at rest and graded levels of exercise on a treadmill up to 60-65% of maximal aerobic capacity. To test for effects of training, HR and V˙O2 were measured in female dogs, before and after a training period, and after an adjacent training pause to test for reversibility of potential effects. Least squares regression was applied to describe the relationship between HR and V˙O2. The applied training had no statistically significant effect on the HR-V˙O2 regression. A general regression line from all data collected was prepared to establish a general predictive equation for energy expenditure from HR in FBI dogs. The regression equation established in this study enables fast estimation of energy requirement for running activity. The equation is valid for large dogs weighing around 30 kg that run at ground level up to 15 km/h with a heart rate maximum of 190 bpm irrespective of the training level.

Interactive effects of body position and perceived exertion during spinning exercises

Spinning is a popular group exercise taught in health and fitness facilities worldwide. Throughout a Spinning workout session, intensity is variable and is controlled by body position on the Spinning stationary cycle and perceived resistance. This study examined the effects of 3 body positions and 4 levels of perceived exertion (RPE) on cardiorespiratory response and vastus lateralis normalized electromyographical activity (NrmsEMGVL). Eleven participants (24.4 ± 6.3 years) with 3.2 ± 2.2 years of Spinning experience completed twelve 3-minute randomly assigned Spinning conditions across 4 separate testing days after an 8-hour fast. Conditions were determined by body position (seated, running, and standing climb [SC]) and RPE (low, low-medium, medium-high, and high). Cardiorespiratory data and NrmsEMGVL were recorded continuously during each Spinning condition. Respiratory rate and oxygen consumption were significantly higher for running and SC than seated, and minute ventilation was significantly higher for running than seated. All cardiorespiratory values were higher at medium-high and high RPE, than low or medium-low RPE, and high RPE generated higher respiratory rate and respiratory exchange ratio than medium-high RPE. Significant body position × RPE interactions were observed for heart rate (HR) and NrmsEMGVL with running and SC producing higher HRs than seated at low and high RPE, and running producing higher NrmsEMGVL than seated at low RPE. Results indicate that running and SC provide the greatest cardiorespiratory responses, and maximal efforts are not needed for these responses. Additionally, HR seems to be a poor marker of oxygen consumption, especially at high RPEs.

Anaerobic Threshold and Salivary α-amylase during Incremental Exercise

[Purpose] The purpose of this study was to clarify the validity of salivary α-amylase as a method of quickly estimating anaerobic threshold and to establish the relationship between salivary α-amylase and double-product breakpoint in order to create a way to adjust exercise intensity to a safe and effective range. [Subjects and Methods] Eleven healthy young adults performed an incremental exercise test using a cycle ergometer. During the incremental exercise test, oxygen consumption, carbon dioxide production, and ventilatory equivalent were measured using a breath-by-breath gas analyzer. Systolic blood pressure and heart rate were measured to calculate the double product, from which double-product breakpoint was determined. Salivary α-amylase was measured to calculate the salivary threshold. [Results] One-way ANOVA revealed no significant differences among workloads at the anaerobic threshold, double-product breakpoint, and salivary threshold. Significant correlations were found between anaerobic threshold and salivary threshold and between anaerobic threshold and double-product breakpoint. [Conclusion] As a method for estimating anaerobic threshold, salivary threshold was as good as or better than determination of double-product breakpoint because the correlation between anaerobic threshold and salivary threshold was higher than the correlation between anaerobic threshold and double-product breakpoint. Therefore, salivary threshold is a useful index of anaerobic threshold during an incremental workload.

Narita target heart rate equation underestimates the predicted adequate exercise level in sedentary young boys

Purpose

Optimal training intensity and the adequate exercise level for physical fitness is one of the most important interests of coaches and sports physiologists. The aim of this study was to investigate the validity of the Narita et al target heart rate equation for the adequate exercise training level in sedentary young boys.

Methods

Forty two sedentary young boys (19.07±1.16 years) undertook a blood lactate transition threshold maximal treadmill test to volitional exhaustion with continuous respiratory gas measurements according to the Craig method. The anaerobic threshold (AT) of the participants then was calculated using the Narita target heart rate equation.

Results

Hopkin's spreadsheet to obtain confidence limit and the chance of the true difference between gas measurements and Narita target heart rate equation revealed that the Narita equation most likely underestimates the measured anaerobic threshold in sedentary young boys (168.76±15 vs. 130.08±14.36) (Difference ±90% confidence limit: 38.1±18). Intraclass correlation coefficient (ICC) showed a poor agreement between the criterion method and Narita equation (ICC= 0.03).

Conclusion

According to the results, the Narita equation underestimates the measured AT. It seems that the Narita equation is a good predictor of aerobic not AT which can be investigated in the future studies.

Programming exercise intensity in patients on beta-blocker treatment: the importance of choosing an appropriate method

AIM

To verify the usefulness of current recommended level of target exercise heart rate (HR) and of different HR-based methods for calculating target HR in patients with and without beta-blocker treatment.

METHODS

We studied 53 patients not treated with beta-blocker and 159 patients on beta-blocker treatment. All patients underwent a maximal exercise test with gas analysis, and first ventilatory threshold (VT1 or aerobic threshold), second ventilatory threshold (VT2 or anaerobic threshold), time of exercise, maximum load, metabolic parameters, HR at rest (HRrest), HRpeak, HR at VT1 (HRVT1) and at VT2 (HRVT2), and 75, 80, and 85% of HRmax (HR75%, HR80%, HR85%) were calculated. Exercise HR was also determined using the Karvonen formula, applying 60, 70, and 80% of the heart rate reserve (HRR) (HRKarv0.6, HRKarv0.7, and HRKarv0.8).

RESULTS

This study included 102 patients on a beta-blocker and 39 not treated with negative cronotropic effect drugs. Maximum load, metabolic parameters, HRrest, HRpeak, HRVT1, and HRVT2 were significantly lower in patients on beta-blocker treatment. The proportion of patients with a HR75%, HR80%, HR85%, ​​HRKarv0.6, HRKarv0.7, and HRKarv0.8 <VT1 and >VT2 was very high and depended on whether patients were on beta-blocker treatment.

CONCLUSIONS

Prescribed exercise intensity should be within VT1 and VT2, so that the efficacy and safety is guaranteed. If determining VT1 and VT2 is not possible, HR-based methods can be used, but with caution. In fact, there will be always a proportion of patients training below VT1 or above VT2. On the other hand, recommendations for patients on a beta-blocker should be different from patients not receiving a beta-blocker. Patients not treated with a beta-blocker should exercise at HRKarv0.7 or at HR85%. In patients on a beta-blocker, we recommend preferentially a target HR of HRKarv0.6 or HR80%.

Direct and indirect lactate oxidation in trained and untrained men

Lactate has been shown to be an important oxidative fuel. We aimed to quantify the total lactate oxidation rate (Rox) and its direct vs. indirect (glucose that is gluconeogenically derived from lactate and subsequently oxidized) components (mg·kg(-1)·min(-1)) during rest and exercise in humans. We also investigated the effects of endurance training, exercise intensity, and blood lactate concentration ([lactate]b) on direct and indirect lactate oxidation. Six untrained (UT) and six trained (T) men completed 60 min of constant load exercise at power outputs corresponding to their lactate threshold (LT). T subjects completed two additional 60-min sessions of constant load exercise at 10% below the LT workload (LT-10%), one of which included a lactate clamp (LC; LT-10%+LC). Rox was higher at LT in T [22.7 ± 2.9, 75% peak oxygen consumption (Vo2peak)] compared with UT (13.4 ± 2.5, 68% Vo2peak, P < 0.05). Increasing [lactate]b (LT-10%+LC, 67% Vo2peak) significantly increased lactate Rox (27.9 ± 3.0) compared with its corresponding LT-10% control (15.9 ± 2.2, P < 0.05). Direct and indirect Rox increased significantly from rest to exercise, and their relative partitioning remained constant in all trials but differed between T and UT: direct oxidation comprised 75% of total lactate oxidation in UT and 90% in T, suggesting the presence of training-induced adaptations. Partitioning of total carbohydrate (CHO) use showed that subjects derived one-third of CHO energy from blood lactate, and exogenous lactate infusion increased lactate oxidation significantly, causing a glycogen-sparing effect in exercising muscle.

Low endogenous thrombin potential in trained subjects

INTRODUCTION

A paradox seems to exist: exercising leads to clotting activation in conventional clotting tests, but exercising persons have a low risk of thrombosis. In this study we tried to evaluate the effect of exercise performance status on in vitro plasma thrombin generation, which represents an overall function test of hemostasis.

MATERIALS AND METHODS

We compared 56 trained subjects to 98 healthy age matched sedentary volunteers. Blood samples were analyzed for thrombin generation using calibrated automated thrombography. Microparticles were quantified using ELISA. Additionally prothrombin fragments 1 + 2, thrombin-antithrombin complex, tissue factor pathway inhibitor, antithrombin and prothrombin were measured. The group of the trained subjects performed an incremental cycle-ergometer exercise test after taking the blood sample.

RESULTS

A significantly lower endogenous thrombin potential was observed in the group of the trained subjects compared to the sedentary individuals (p = 0.007). Microparticles (ELISA) were significantly lower in the trained subjects compared to the sedentary subjects (p = 0.001). Prothrombin fragments 1 + 2 (p < 0.001) and thrombin-antithrombin complex (p = 0.01) were significant higher in the trained subjects and antithrombin (p = 0.02) as well as prothrombin (p < 0.0001) were significantly lower in this group, whereas tissue factor pathway inhibitor values did not show significant differences. Both maximal and submaximal power output was significantly negatively related to endogenous thrombin potential (r = -0.43, r = -0.45) and thrombin peak (r = -0.44, r = -0.42).

CONCLUSIONS

Trained subjects have a lower endogenous thrombin potential than sedentary subjects possibly explaining the lower incidence of thrombosis in this group despite a higher acute clotting activation during strenuous exercise.

Energy expenditure and sex differences of golf playing

The purpose of the study was to assess the average physical intensity and energy expenditure during a single round of golf on hilly and flat courses in a heterogeneous group of healthy men and women of varying age and golf handicap. Forty-two males and 24 females completed an incremental cycle-ergometer exercise test to determine exercise performance markers. The heart rate (HR), duration, distance, walking speed, ascent and descent were measured via a global positioning system (GPS)/HR monitor during the game and energy expenditure was calculated. Playing 9 or 18-holes of golf, independent of the golf course design, the average HR was not significantly different between sexes or the subgroups. The intensities were light with respect to the percentage of maximal HR and metabolic equivalents of task (METs). Total energy expenditure of all participants was not significantly different for hilly (834 ± 344 kcal) vs. flat courses (833 ± 295 kcal) whereas male players expended significantly greater energy than female players (926 ± 292 vs. 556 ± 180 kcal), but did not have significantly greater relative energy expenditure (2.8 ± 0.8 vs. 2.2 ± 0.7 METs). As a high volume physical activity, playing golf is suggested to yield health benefits. Since the intensity was well below recommended limits, golf may have health related benefits unrelated to the intensity level of the activity.

Gluconeogenesis and hepatic glycogenolysis during exercise at the lactate threshold

Because the maintenance of glycemia is essential during prolonged exercise, we examined the effects of endurance training, exercise intensity, and plasma lactate concentration ([lactate]) on gluconeogenesis (GNG) and hepatic glycogenolysis (GLY) in fasted men exercising at, and just below, the lactate threshold (LT), where GNG precursor lactate availability is high. Twelve healthy men (6 untrained, 6 trained) completed 60 min of constant-load exercise at power outputs corresponding to their individual LT. Trained subjects completed two additional 60-min sessions of constant-load exercise: one at 10% below the LT workload (LT-10%), and the other with a lactate clamp (LT-10%+LC) to match the [lactate] of the LT trial. Flux rates were determined by primed continuous infusion of [6,6-(2)H(2)]glucose, [3-(13)C]lactate, and [(13)C]bicarbonate tracers during 90 min of rest and 60 min of cycling. Exercise at LT corresponded to 67.6 ± 1.3 and 74.8 ± 1.7% peak O(2) consumption in the untrained and trained subjects, respectively (P < 0.05). Relative exercise intensity was matched between the untrained group at LT and the trained group at LT-10%, and [lactate] during exercise was matched in the LT and LT-10%+LC trials via exogenous lactate infusion. Glucose kinetics (rate of appearance, rate of disposal, and metabolic clearance rate) were augmented with the lactate clamp. GNG was decreased in the trained subjects exercising at LT and LT-10% compared with the untrained subjects, but increasing [lactate] in the LT-10%+LC trial significantly increased GNG (4.4 ± 0.9 mg·kg(-1)·min(-1)) compared with its corresponding control (1.7 ± 0.4 mg·kg(-1)·min(-1), P < 0.05). Hepatic GLY was higher in the trained than untrained subjects, but not significantly different across conditions. We conclude that GNG plays an essential role in maintaining total glucose production during exercise in fasted men, regardless of training state. However, endurance training increases the ability to achieve a higher relative exercise intensity and absolute power output at the LT without a significant decrease in GNG. Furthermore, raising systemic precursor substrate availability increases GNG during exercise, but not at rest.

Blood lactate concentration at the maximal lactate steady state is not dependent on endurance capacity in healthy recreationally trained individuals

The aim of the study was to investigate the independent relationship between maximal lactate steady state (MLSS), blood lactate concentration [La] and exercise performance as reported frequently. Sixty-two subjects with a wide range of endurance performance (MLSS power output 199 ± 55 W; range: 100-302 W) were tested on an electronically braked cycle ergometer. One-min incremental exercise tests were conducted to determine maximal variables as well as the respiratory compensation point (RCP) and the second lactate turn point (LTP2). Several continuous exercise tests were performed to determine the MLSS. Subjects were divided into three clusters of exercise performance. Dietary control was employed throughout all testing. No significant correlation was found between MLSS [La] and power output at MLSS. Additionally, the three clusters of subjects with different endurance performance levels based on power output at MLSS showed no significant difference for MLSS [La]. MLSS [La] was not significantly different between men and women (average of 4.80 ± 1.50 vs. 5.22 ± 1.52 mmol l(-1)). MLSS [La] was significantly related to [La] at RCP, LTP2 and at maximal power. The results of this study support previous findings that MLSS [La] is independent of endurance performance. Additionally, MLSS [La] was not influenced by sex. Correlations found between MLSS [La] and [La] at maximal power and at designated anaerobic thresholds indicate only an association of [La] response during incremental and MLSS exercise when utilizing cycle ergometry.

Strong relationship between heart rate deflection point and ventilatory threshold in trained rowers

The purpose of this study was to assess the relationship between heart rate deflection point (HRDP) and ventilatory threshold (VT) to the physiological and performance variables in a relatively large group of trained men rowers. We proposed the hypothesis that physiological and performance variables corresponding to HRDP are not significantly different from corresponding variables at VT, which would justify the use of HRDP as a simple, affordable, and noninvasive method of anaerobic threshold assessment in trained rowers. Eighty-nine trained men rowers (mean ± SD: age 21.2 ± 4.1 years; stature 1.89 ± 0.06 m; body mass 89.2 ± 8.4 kg; VO₂max [maximum oxygen uptake] 5.39 ± 0.62 L/min⁻¹) completed an incremental rowing ergometer exercise test to exhaustion. Three independent, experienced observers determined both HRDP and VT. HRDP was determined by visual and computer-aided regression analyses and was evident in all rowers. The main findings include (a) there is a strong relationship among all observed physiological and performance variables corresponding to HR(HRDP) and HR(VT) (r = 0.79-0.96; p < 0.001) and (b) power output, oxygen uptake, ventilation, tidal volume and breathing rate corresponding to HR(HRDP) and HR(VT) were not significantly different (p ≥ 0.011), whereas HR(HRDP) was slightly but significantly higher than HR(VT) (174.5 vs. 172.8 beats·min⁻¹; p = 0.003). The standard error of the estimate in predicting the HR(VT) based on HR(HRDP) was 5.1 beats·min⁻¹. The subsequent data suggest that, in general, trained rowers may be able to periodically assess their aerobic endurance and evaluate the effects of training programs using the HRDP method.

Special needs to prescribe exercise intensity for scientific studies

There is clear evidence regarding the health benefits of physical activity. These benefits follow a dose-response relationship with a particular respect to exercise intensity. Guidelines for exercise testing and prescription have been established to provide optimal standards for exercise training. A wide range of intensities is used to prescribe exercise, but this approach is limited. Usually percentages of maximal oxygen uptake (VO₂) or heart rate (HR) are applied to set exercise training intensity but this approach yields substantially variable metabolic and cardiocirculatory responses. Heterogeneous acute responses and training effects are explained by the nonuniform heart rate performance curve during incremental exercise which significantly alters the calculations of %HR_max and %HRR target HR data. Similar limitations hold true for using %VO_2max and %VO₂R. The solution of these shortcomings is to strictly apply objective submaximal markers such as thresholds or turn points and to tailor exercise training within defined regions.

Value of the Application of the Heart Rate Performance Curve in Sports

The heart rate performance curve (HRPC) has been shown to be nonlinearly related to work load. This phenomenon has been used to determine a defection point and to be related to the lactate anaerobic threshold. The original method was heavily criticized, and the method was challenged by several authors. However, some authors also demonstrated a high value for this method’s application in various sports conditions. Unfortunately, the HRPC was shown to be not uniform and three different patterns were found. Basic investigations have shown a dependence of the HR-defection on beta1-receptor sensitivity, which gave a plausible explanation of the phenomenon. Important details regarding the testing protocol and the method of turn point determination are given in this review. As a conclusion, we may state that based on numerous studies the method is plausible and valid to determine aerobic exercise performance in various laboratory ergometer and specific sports-related field conditions. Standard protocol conditions adjusted to the exercise performance level of subjects and a computer-supported determination of turn points are necessary to obtain reliable results. Large-scale investigations to validate the heart rate turn point with maximal lactate steady state are still needed. However, from the available literature, the application of this noninvasive method can be recommended to determine aerobic exercise performance in various sports. This noninvasive test is easy to perform repeatedly, which gives interesting possibilities for the monitoring of training adaptation in the short term, such as altitude training or specifc taper forms.

Identification of a Vo2 deflection point coinciding with the heart rate deflection point and ventilatory threshold in cycling

The purposes of this study were to compare the patterns of the work rate (WR)-Vo2 and WR-heart rate (HR) relationships in incremental cycling, to ascertain the occurrence of a Vo2 deflection (Vo2def) coinciding with the HR deflection point (HRdef ), and to determine whether the Vo2def, if present, coincides with the ventilatory anaerobic threshold (VT). Twenty-four professional cyclists performed a maximal incremental test on a wind-load cycle ergometer. Work rate, HR, Vo2, and Vco2 were recorded. The WR-Vo2 relationships obtained were linear up to submaximal WR and curvilinear thereafter and thus described a Vo2def. The WR and Vo2 at Vo2def were mathematically determined for all subjects. The ratio of DeltaWR.DeltaVo2 up to Vo2def was significantly lower than that above Vo2def (90 +/- 11 W.L.min versus 133 +/- 35 W.L.min, p < 0.0001). The WR-HR relationships obtained were linear up to submaximal WR and curvilinear thereafter. The WR and HR at HRdef were mathematically determined for all subjects. The WR values at Vo2def and at HRdef (329 +/- 32 W and 326 +/- 34 W) were significantly correlated (R = 0.96, p < 0.0001) and in good concordance (limits of agreement from -4.7% to 3.2%, Bland-Altman analysis). The Vo2 at VT was then determined for all subjects. The Vo2 values at Vo2def and at VT were significantly correlated (R = 0.99, p < 0.0001) and in strong concordance (limits of agreement from -1.9% to 1.0%, Bland-Altman analysis). In conclusion, a Vo2def coinciding with HRdef and VT was shown. This confirms that the determination of the WR-HR relationship and of HRdef is a practical and noninvasive means of identifying anaerobic threshold.

Single bouts of exercise affect albumin redox state and carbonyl groups on plasma protein of trained men in a workload-dependent manner

The purpose of this study was to investigate the effect of single bouts of exercise at three different intensities on the redox state of human serum albumin (HSA) and on carbonyl groups on protein (CP) concentrations in plasma. Trained men [n = 44, maximal oxygen consumption (Vo(2max)): 55 +/- 5 ml.kg(-1).min(-1), nonsmokers, 34 +/- 5 years of age] from a homogenous population, volunteers from a police special forces unit, were randomly assigned to perform on a cycle ergometer either at 70% (n = 14), 75% (n = 14), or 80% (n = 16) of Vo(2max) for 40 min. Blood was collected before exercise, immediately after the exercise test (IE), and 30 min after each test (30M) and 30 h after each test (30H). The reduced fraction of HSA, human mercaptalbumin (HMA), decreased at all three exercise intensities IE and 30M, returning to preexercise values by 30H (P < 0.05). HMA was primarily oxidized to its reversible fraction human nonmercaptalbumin 1 (HNA1). CP concentrations increased at 75% of Vo(2max) IE and 30M with a tendency (P < 0.1) and at 80% Vo(2max) IE and 30M significantly, returning to preexercise concentrations by 30H (P < 0.01). These results indicate that the HSA redox system in plasma is activated after a single bout of cycle ergometer exercise at 70% Vo(2max) and 40 min duration. The extent of the HSA modification increased with exercise intensity. Oxidative protein damage, as indicated by CP, was only significantly increased at 80% Vo(2max) intensity in this homogenous cohort of trained men.