Mechanical power output during cycling: The efficacy of mobile power meters for monitoring exercise intensity during cycling

One of the most meaningful technical innovations in cycling over the past two decades was the development of mobile power meters. With the ability to measure the physical strain under “real world” outdoor conditions, the knowledge of the demand during cycling has improved enormously. Power output has been described as the most direct measure of intensity during cycling and consequently power meters becomes a popular tool to monitor the training and racing of cyclists. However, only limited research data are available on the utilisation of power meters for performance assessment in the field or the analysis of training data. Therefore, the aims of the thesis were to evaluate the ecological validity of a field test, to provide an extensive insight into the longitudinal training strategies of world-class cyclists and to investigate the effects of interval training in the field at difference cadences. The first study aimed to assess the reproducibility of power output during a 4-min (TT4) and a 20-min (TT20) time-trial and the relationship with performance markers obtained during a laboratory graded exercise test (GXT). Ventilatory and lactate thresholds during a GXT were measured in competitive male cyclists (n = 15; VO2max 67 ± 5 mL . min−1 . kg−1; Pmax 440 ± 38 W ). Two 4- min and 20-min time-trials were performed on flat roads. Strong intraclass-correlations for TT4 (r = 0.98; 95 % CL: 0.92-0.99) and TT20 (r = 0.98; 95 % CL: 0.95-0.99) were observed. TT4 showed a bias ± random error of −0.8 ± 23W or −0.2 ± 5.5%. During TT20 the bias ± random error was −1.8 ± 14 W or 0.6 ± 4.4 %. Both time-trials were strongly correlated with performance measures from the GXT (p < 0.001). Significant differences were observed between power output during TT4 and GXT measures (p < 0.001). No significant differences were found between TT20 and power output at the second lactate-turn-point (LTP 2) (p = 0.98) and respiratory compensation point (RCP) (p = 0.97). In conclusion, TT4 and TT20 mean power outputs are reliable predictors of endurance performance. TT20 was in agreement with power output at RCP and LTP 2. Study two aimed to quantify power output (PO) and heart rate (HR) distributions across a whole season in elite cyclists. Power output and heart rate were monitored for 11 months in ten male (age: 29.1 ± 6.7 y; VO2max: 66.5 ± 7.1 mL . min−1 . kg−1) and one female (age: 23.1y; VO2max: 71.5 mL . min−1 . kg−1) cyclist. In total, 1802 data sets were sampled and divided into workout categories according to training goals. The PO at the RCP was used to determine seven intensity zones (Z1-Z7). PO and HR distributions into Z1-Z7 were calculated for all data and workout categories. The ratio of mean PO to RCP (intensity factor, IF) was assessed for each training session and for each interval during the training sessions (IFINT). Variability of PO was calculated as coefficient of variation (CV ). There was no significant difference in the distribution of PO and HR for the total season (p = 0.15), although significant differences between workout categories were observed (p < 0.001). Compared with PO, HR distributions showed a shift from low to high intensities. IF was significantly different between categories (p < 0.001). The IFINT was related to performance (p < 0.01), although the overall IF for the session was not. Also, total training time was related to performance (p < 0.05). The variability in PO was inversely associated with performance (p < 0.01). In conclusion, HR accurately reflects exercise intensity over a total season or low intensity workouts but is limited when applied to high intensity workouts. Better performance by cyclists was characterised by lower variability in PO, greater training volume and the production of higher exercise intensities during intervals. The third study tested the effects of low-cadence (60 rev . min−1) uphill (Int60) or high-cadence (100 rev . min−1) flat (Int100) interval training on PO during 20 min uphill (TTup) and flat (TTflat) time-trials. Eighteen male cyclists (VO2max: 58.6 ± 5.4 mL . min−1 . kg−1) were randomly assigned to Int60, Int100 or a control group (Con). The interval training comprised of two training sessions per week over four weeks, which consisted of 6 bouts of 5 min at the PO at RCP. For the control group, no interval training was conducted. A two-factor ANOVA revealed significant increases on performance measures obtained from GXT (Pmax: 2.8 ± 3.0 %; p < 0.01; PO and VO2 at RCP: 3.6 ± 6.3 % and 4.7 ± 8.2 %, respectively; p < 0.05; and VO2 at ventilatory threshold: 4.9 ± 5.6 %; p < 0.01), with no significant group effects. Significant interactions between group and the uphill and flat time-trials, pre vs. post-training on time-trial PO were observed (p < 0.05). Int60 increased PO during both, TTup (4.4 ± 5.3 %) and TTflat (1.5 ± 4.5 %), whereas the changes were − 1.3 ± 3.6 %; 2.6 ± 6.0 % for Int100 and 4.0 ± 4.6 %; − 3.5 ± 5.4 % for Con, during TTup and TTflat, respectively. PO was significantly higher during TTup than TTflat (4.4 ± 6.0 %; 6.3 ± 5.6 %; pre and post-training, respectively; p < 0.001). These findings suggest that higher forces during the low-cadence intervals are potentially beneficial to improve performance. In contrast to the GXT, the time-trials are ecologically valid to detect specific performance adaptations

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, ten male participants (age: 24.9±2.1 yrs; height: 180.8±5.8 cm; body mass: 75.3±8.6 kg; V ̇O2peak 52.9±3.1 mL∙min-1∙kg-1) performed three time-to-exhaustion runs on a treadmill followed by three 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 ±75.5m 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 testing method can consequently be recommended to coaches and practitioners, however a questionable level of agreement indicates to use D´ with caution

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 ecological valid maximal effort time-trials (TTs) under laboratory conditions. After an initial incremental exercise test, ten well-trained male triathletes (age: 28.5 ± 4.7 yrs; body mass: 73.3 ± 7.9 kg; height: 1.80 ± 0.07 m; maximal aerobic power (MAP): 328.6 ± 41.2 W) performed three testing sessions (Familiarization, Test I and Test II) each comprising three TTs (12 min, 7 min 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 measure 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 the repeated tests, ICC and CoV values improved notably after the Familiarization trial. Our novel findings indicate that for both, CP and W´ post familiarization ICC and CoV values indicated high reliability. It is therefore advisable to familiarize well-trained athletes when determining the power-duration relationship using TTs under laboratory conditions

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 to 15 min. Ten triathletes (mean±SD age: 31.0±5.7yrs; height: 1.81±0.05m; body mass: 76.5±6.8kg) performed two randomly assigned field-tests to determine critical speed (CS) and the total distance covered above CS (D´). CS and D´ 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=D´x1/t+CS) was used to determine parameter estimates. Significant differences were found for CS (P=.026), but not for D´ (P=.123). The effect size for CS (d=.305) was considered small, whilst that for D´ was considered moderate (d=.742). CS was significantly correlated between protocols (r=.934; P<.001), however, no correlation was found for D´ (r=.053; P=.884). The 95% limits of agreement were ±0.28m∙s-1 and ±73.9m for CS and D´, respectively. These findings demonstrate that the choice of exhaustive times within commonly accepted durations, results in different estimates of CS and D´ 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

Validation of automated detection of physical and mental stress during work in a Hühnermobil 225

Introduction The effects of the use of mobile henhouses and their equipment on the physical and mental stress of farmers in the organic egg production, and the reliability of the sensor-based detection of these in work processes are insufficiently known. There are neither measurement results nor key figures, according to operation and gender especially, available in the literature. Objective The aim of this case study is to quantify the physical and mental stress of work processes on the basis of heart rate and the Baevsky Stress Index, as measured by the ECG- and activity sensor Movisens®, which is used mainly in the sports and rehabilitation sectors. To analyse the impact, daily routine work was divided into operations and the data collected for this purpose analysed descriptively and analytically. Conclusions In summary, it can be concluded that measurement technology has the potential to capture the activity-related exceedances of the endurance limit of the work severity by means of the heart rate reliably, to identify risk areas of employment and to quantify stress situations. The accuracy and reliability of data acquisition with Movisens® should be validated by a larger sample size and further measurements. In particular, the algorithm for calculating the data to quantify the mental and physical stress without movement needs to be improved significantly through further development

Mechanical power output during cycling : the efficacy of mobile power meters for monitoring exercise intensity during cycling

One of the most meaningful technical innovations in cycling over the past two decades was the development of mobile power meters. With the ability to measure the physical strain under “real world” outdoor conditions, the knowledge of the demand during cycling has improved enormously. Power output has been described as the most direct measure of intensity during cycling and consequently power meters becomes a popular tool to monitor the training and racing of cyclists. However, only limited research data are available on the utilisation of power meters for performance assessment in the field or the analysis of training data. Therefore, the aims of the thesis were to evaluate the ecological validity of a field test, to provide an extensive insight into the longitudinal training strategies of world-class cyclists and to investigate the effects of interval training in the field at difference cadences. The first study aimed to assess the reproducibility of power output during a 4-min (TT4) and a 20-min (TT20) time-trial and the relationship with performance markers obtained during a laboratory graded exercise test (GXT). Ventilatory and lactate thresholds during a GXT were measured in competitive male cyclists (n = 15; VO2max 67 ± 5 mL . min−1 . kg−1; Pmax 440 ± 38 W ). Two 4- min and 20-min time-trials were performed on flat roads. Strong intraclass-correlations for TT4 (r = 0.98; 95 % CL: 0.92-0.99) and TT20 (r = 0.98; 95 % CL: 0.95-0.99) were observed. TT4 showed a bias ± random error of −0.8 ± 23W or −0.2 ± 5.5%. During TT20 the bias ± random error was −1.8 ± 14 W or 0.6 ± 4.4 %. Both time-trials were strongly correlated with performance measures from the GXT (p < 0.001). Significant differences were observed between power output during TT4 and GXT measures (p < 0.001). No significant differences were found between TT20 and power output at the second lactate-turn-point (LTP 2) (p = 0.98) and respiratory compensation point (RCP) (p = 0.97). In conclusion, TT4 and TT20 mean power outputs are reliable predictors of endurance performance. TT20 was in agreement with power output at RCP and LTP 2. Study two aimed to quantify power output (PO) and heart rate (HR) distributions across a whole season in elite cyclists. Power output and heart rate were monitored for 11 months in ten male (age: 29.1 ± 6.7 y; VO2max: 66.5 ± 7.1 mL . min−1 . kg−1) and one female (age: 23.1y; VO2max: 71.5 mL . min−1 . kg−1) cyclist. In total, 1802 data sets were sampled and divided into workout categories according to training goals. The PO at the RCP was used to determine seven intensity zones (Z1-Z7). PO and HR distributions into Z1-Z7 were calculated for all data and workout categories. The ratio of mean PO to RCP (intensity factor, IF) was assessed for each training session and for each interval during the training sessions (IFINT). Variability of PO was calculated as coefficient of variation (CV ). There was no significant difference in the distribution of PO and HR for the total season (p = 0.15), although significant differences between workout categories were observed (p < 0.001). Compared with PO, HR distributions showed a shift from low to high intensities. IF was significantly different between categories (p < 0.001). The IFINT was related to performance (p < 0.01), although the overall IF for the session was not. Also, total training time was related to performance (p < 0.05). The variability in PO was inversely associated with performance (p < 0.01). In conclusion, HR accurately reflects exercise intensity over a total season or low intensity workouts but is limited when applied to high intensity workouts. Better performance by cyclists was characterised by lower variability in PO, greater training volume and the production of higher exercise intensities during intervals. The third study tested the effects of low-cadence (60 rev . min−1) uphill (Int60) or high-cadence (100 rev . min−1) flat (Int100) interval training on PO during 20 min uphill (TTup) and flat (TTflat) time-trials. Eighteen male cyclists (VO2max: 58.6 ± 5.4 mL . min−1 . kg−1) were randomly assigned to Int60, Int100 or a control group (Con). The interval training comprised of two training sessions per week over four weeks, which consisted of 6 bouts of 5 min at the PO at RCP. For the control group, no interval training was conducted. A two-factor ANOVA revealed significant increases on performance measures obtained from GXT (Pmax: 2.8 ± 3.0 %; p < 0.01; PO and VO2 at RCP: 3.6 ± 6.3 % and 4.7 ± 8.2 %, respectively; p < 0.05; and VO2 at ventilatory threshold: 4.9 ± 5.6 %; p < 0.01), with no significant group effects. Significant interactions between group and the uphill and flat time-trials, pre vs. post-training on time-trial PO were observed (p < 0.05). Int60 increased PO during both, TTup (4.4 ± 5.3 %) and TTflat (1.5 ± 4.5 %), whereas the changes were − 1.3 ± 3.6 %; 2.6 ± 6.0 % for Int100 and 4.0 ± 4.6 %; − 3.5 ± 5.4 % for Con, during TTup and TTflat, respectively. PO was significantly higher during TTup than TTflat (4.4 ± 6.0 %; 6.3 ± 5.6 %; pre and post-training, respectively; p < 0.001). These findings suggest that higher forces during the low-cadence intervals are potentially beneficial to improve performance. In contrast to the GXT, the time-trials are ecologically valid to detect specific performance adaptations.EThOS - Electronic Theses Online ServiceGBUnited Kingdo

Validation of automated detection of physical and mental stress during work in a Hühnermobil 225

Introduction The effects of the use of mobile henhouses and their equipment on the physical and mental stress of farmers in the organic egg production, and the reliability of the sensor-based detection of these in work processes are insufficiently known. There are neither measurement results nor key figures, according to operation and gender especially, available in the literature. Objective The aim of this case study is to quantify the physical and mental stress of work processes on the basis of heart rate and the Baevsky Stress Index, as measured by the ECG- and activity sensor Movisens®, which is used mainly in the sports and rehabilitation sectors. To analyse the impact, daily routine work was divided into operations and the data collected for this purpose analysed descriptively and analytically. Conclusions In summary, it can be concluded that measurement technology has the potential to capture the activity-related exceedances of the endurance limit of the work severity by means of the heart rate reliably, to identify risk areas of employment and to quantify stress situations. The accuracy and reliability of data acquisition with Movisens® should be validated by a larger sample size and further measurements. In particular, the algorithm for calculating the data to quantify the mental and physical stress without movement needs to be improved significantly through further development

Comparative determination of physical stress and strain on milkers in milking parlours on dairy farms in Upper Austria, using ECG, an activity sensor and spirometer

To-date, the impact of modern milking parlors in dairy farming on physical strain has not been the subject of many studies. Therefore, this case study aims to record and evaluate the physical strain during the entire milking process, including the oxygen consumption (VO2), heart rate (HR) and metabolic rate (WkJ, Watt) of milkers. The recording was conducted with a portable respiratory gas analysis system and an ECG and activity sensor on 4 dairy farms in Austria. Eight subjects aged from 45–52 years, with a mean age 50±2.4 SD, participated and the data were recorded during the milking process in 2 types of milking parlours. For assessment, the entire milking process was divided into preparation, milking and follow-up work. The entire milking process was performed with an average oxygen consumption of 46.5 l/h and a heart rate of 98 bpm, which is below the anaerobic threshold; whereas in the preparation and follow-up work, this threshold was exceeded. Generally, during the milking process, a moderate physical strain (32.4%) and a balanced metabolic rate (143 watt/m2) were determined. The physical strain in female milkers was 9.2% higher than in male milkers throughout the entire process. Reduction of physical strain can be achieved through additional breaks, reduced work speed, division of labour and technical devices

Reliability of the Single-Visit Field Test of Critical Speed in Trained and Untrained Adolescents

Recent studies in adults have shown that the critical intensity during running and cycling estimated from three prediction trials interspersed by 30 min is valid and reliable. To establish the reliability of the single-visit field test to determine critical speed (CS) and the distance above critical speed (D′) in adolescents, 29 trained and 14 untrained participants (mean ± SD age: 17.5 ± 0.5 years) performed three tests on a 400-m outdoor track separated by 48 h. Each test consisted of three distances selected to result in finishing times between 2 and 15 min that must be completed as fast as possible. CS and D′ were modeled using the linear 1/time model (Speed = D′(1/t) + CS). While the coefficient of variation (CV) of CS was between 2.4% and 4.3%, the CV of D′ was 9.3% to 13.6%. Also the intraclass correlation coefficient ranged from 0.919 to 0.983 for CS and from 0.325 to 0.828 for D′. The results show that the single-visit field test provides reliable estimates of CS but not D′ in trained and untrained adolescents

Comparative determination of physical stress and strain on milkers in milking parlours on dairy farms in Upper Austria, using ECG, an activity sensor and spirometer

To-date, the impact of modern milking parlors in dairy farming on physical strain has not been the subject of many studies. Therefore, this case study aims to record and evaluate the physical strain during the entire milking process, including the oxygen consumption (VO2), heart rate (HR) and metabolic rate (WkJ, Watt) of milkers. The recording was conducted with a portable respiratory gas analysis system and an ECG and activity sensor on 4 dairy farms in Austria. Eight subjects aged from 45–52 years, with a mean age 50±2.4 SD, participated and the data were recorded during the milking process in 2 types of milking parlours. For assessment, the entire milking process was divided into preparation, milking and follow-up work. The entire milking process was performed with an average oxygen consumption of 46.5 l/h and a heart rate of 98 bpm, which is below the anaerobic threshold; whereas in the preparation and follow-up work, this threshold was exceeded. Generally, during the milking process, a moderate physical strain (32.4%) and a balanced metabolic rate (143 watt/m2) were determined. The physical strain in female milkers was 9.2% higher than in male milkers throughout the entire process. Reduction of physical strain can be achieved through additional breaks, reduced work speed, division of labour and technical devices