Fixed Blood Lactate Concentration Research Articles

The Science of Handcycling: A Narrative Review.

The aim of this narrative review is to provide insight as to the history, biomechanics, and physiological characteristics of competitive handcycling. Furthermore, based upon the limited evidence available, this paper aims to provide practical training suggestions by which to develop competitive handcycling performance. Handbike configuration, individual physiological characteristics, and training history all play a significant role in determining competitive handcycling performance. Optimal handcycling technique is highly dependent upon handbike configuration. As such, seat positioning, crank height, crank fore-aft position, crank length, and handgrip position must all be individually configured. In regard to physiological determinants, power output at a fixed blood lactate concentration of 4mmol·L-1, relative oxygen consumption, peak aerobic power output, relative upper body strength, and maximal anaerobic power output have all been demonstrated to impact upon handcycling performance capabilities. Therefore, it is suggested that that an emphasis be placed upon the development and frequent monitoring of these parameters. Finally, linked to handcycling training, it is suggested that handcyclists should consider adopting a concurrent strength and endurance training approach, based upon a block periodization model that employs a mixture of endurance, threshold, interval, and strength training sessions. Despite our findings, it is clear that several gaps in our scientific knowledge of handcycling remain and that further research is necessary in order to improve our understanding of factors that determine optimal performance of competitive handcyclists. Finally, further longitudinal research is required across all classifications to study the effects of different training programs upon handcycling performance.

Predicting Cardiorespiratory Fitness in Female Soccer Players: The Basque Female Football Cohort Study.

To develop gender-specific operational equations for prediction of cardiorespiratory fitness in female footballers. Forty-eight semiprofessional female footballers performed an intermittent progressive maximal running test for determination of fixed blood lactate concentration (FBLC) thresholds. Relationships between FBLC thresholds and the physiological responses to submaximal running were examined. Developed equations (n = 48) were compared with equations previously obtained in another investigation performed in males (n = 100). Submaximal velocity associated with 90% maximal heart rate was related to FBLC thresholds (r = .76 to .79; P < .001). Predictive power (R2 = .82 to .94) of a single blood lactate concentration (BLC) sample measured at 10 or 11.5km·h-1 was very high. A single BLC sample taken after a 5-minute running bout at 8.5km·h-1 was related to FBLC thresholds (r = -.71; P < .001). No difference (P = .15) in the regression lines predicting FBLC thresholds from velocity associated with 90% maximal heart rate was observed between the female and male cohorts. However, regressions estimating FBLC thresholds by a single BLC sample were different (P = .002). Velocity associated with 90% maximal heart rate was robustly related to FBLC thresholds and might serve for mass field testing independently of sex. BLC equations accurately predicted FBLC thresholds. However, these equations are gender-specific. This is the first study reporting operational equations to estimate the FBLC thresholds in female footballers. The use of these equations reduces the burden associated with cardiorespiratory testing. Further cross-validation studies are warranted to validate the proposed equations and establish them for mass field testing.

The Effectiveness of a 30-Week Concurrent Strength and Endurance Training Program in Preparation for an Ultra-Endurance Handcycling Challenge: A Case Study.

The aim of the following case study was to evaluate the effectiveness of a 30-week concurrent strength and endurance training program designed to prepare a trained H4 male handcyclist (aged 28y, bilateral, above knee amputee, and body mass 65.6kg) for a 1407-km ultra-endurance handcycling challenge. This observational case study tracked selected physiological measures, training intensity distribution, and total training load over the course of a 30-week concurrent training protocol. Furthermore, the athlete's performance profile during the ultra-endurance challenge was monitored with power output, cadence, speed, and heart rate recorded throughout. Findings revealed considerable improvements in power output at a fixed blood lactate concentration of 4mmol·L-1 (+25.7%), peak aerobic power output (+18.9%), power-to-mass ratio (+18.3%), relative peak oxygen uptake (+13.9%), gross mechanical efficiency (+4.6%), bench press 1-repetition maximum (+4.3%), and prone bench pull 1-repetition maximum (+14.9%). The athlete completed the 1407-km route in a new handcycling world record time of 89:55hours. Average speed was 18.7 (2.1)km·h-1; cadence averaged 70.0 (2.6)rpm, while average power output was 67 (12)W. In terms of internal load, the athlete's average heart rate was 111 (11)beats per minute. These findings demonstrate how a long-term concurrent strength and endurance training program can be used to optimize handcycling performance capabilities in preparation for an ultra-endurance cycling event. Knowledge emerging from this case study provides valuable information that can guide best practices with respect to handcycling training for ultra-endurance events.

The Relationship Between Absolute and Relative Upper-Body Strength and Handcycling Performance Capabilities.

To explore the relationship between absolute and relative upper-body strength and selected measures of handcycling performance. A total of 13 trained H3/H4-classified male handcyclists (mean [SD] age 37 [11]y; body mass 76.6 [10.1]kg; peak oxygen consumption 2.8 [0.6]L·min-1; relative peak oxygen consumption 36.5 [10]mL·kg·min-1) performed a prone bench-pull and bench-press 1-repetition-maximum strength assessment, a 15-km individual time trial, a graded exercise test, and a 15-second all-out sprint test. Relationships between all variables were assessed using Pearson correlation coefficient. Absolute strength measures displayed a large correlation with gross mechanical efficiency and maximum anaerobic power output (P = .05). However, only a small to moderate relationship was identified with all other measures. In contrast, relative strength measures demonstrated large to very large correlations with gross mechanical efficiency, 15-km time-trial velocity, maximum anaerobic power output, peak aerobic power output, power at a fixed blood lactate concentration of 4mmol·L-1, and peak oxygen consumption (P = .05). Relative upper-body strength demonstrates a significant relationship with time-trial velocity and several handcycling performance measures. Relative strength is the product of one's ability to generate maximal forces relative to body mass. Therefore, the development of one's absolute strength combined with a reduction in body mass may influence real-world handcycling race performance.

The Anthropometric, Physiological, and Strength-Related Determinants of Handcycling 15-km Time-Trial Performance.

The aim of this study was to investigate the relationship between selected anthropometric, physiological, and upper-body strength measures and 15-km handcycling time-trial (TT) performance. Thirteen trained H3/H4 male handcyclists performed a 15-km TT, graded exercise test, 15-second all-out sprint, and 1-repetition-maximum assessment of bench press and prone bench pull strength. Relationship between all variables was assessed using a Pearson correlation coefficient matrix with mean TT velocity representing the principal performance outcome. Power at a fixed blood lactate concentration of 4mmol·L-1 (r = .927; P < .01) showed an extremely large correlation with TT performance, whereas relative V˙O2peak (peak oxygen uptake) (r = .879; P < .01), power-to-mass ratio (r = .879; P < .01), peak aerobic power (r = .851; P < .01), gross mechanical efficiency (r = 733; P < .01), relative prone bench pull strength (r = .770; P = .03) relative bench press strength (r = .703; P = .11), and maximum anaerobic power (r = .678; P = .15) all demonstrated a very large correlation with performance outcomes. Findings of this study indicate that power at a fixed blood lactate concentration of 4mmol·L-1, relative V˙O2peak, power-to-mass ratio, peak aerobic power, gross mechanical efficiency, relative upper-body strength, and maximum anaerobic power are all significant determinants of 15-km TT performance in H3/H4 handcyclists.

The acute effects of lower limb blood flow restriction on physiology and performance of competitive cyclists

Background: Training in conjunction with limb Blood flow restriction (BFR) is an increasingly popular method of producing increased physiological stress without the strain of high exercise loads. However little is known about the physiological responses to BFR with trained cyclists or how best to prescribe appropriate BFR training intensities. Purpose: In this study, we investigate the acute responses to different levels of BFR with trained cyclists to enable identification of specific training intensity criteria. Methods: Nine trained male cyclist (age 39.2 ± 8.1 years, height 179.1 ± 6.7 cm, weight 75.4 ± 6.7 kg, Max VO 2 4.4 ± 0.5 L.min -1 ) completed a series of tests under conditions of no BFR (N-BFR; 0mmHg), moderate BFR (M-BFR; ~40mmHg) or high BFR (H-BFR; ~80mmHg). During BFR trials restriction was applied to the proximal thighs using 11cm wide pneumatic cuffs. Testing consisted of an incremental maximal cycle test and a self-paced 3-km time-trial. Measurement of Oxygen uptake (VO 2 ), Muscle Oxygen saturation (MO 2 ) blood lactate concentration (Bla) and perceived exertion (RPE) were taken during the incremental test along with performance data from the time trial.  Physiological responses from the three trials were examined across a range of comparable power outputs and at pre-determined blood lactate concentrations of 2 and 4 Mmol. Results: At comparable power outputs, heart rate and RPE was significantly higher (p>0.05) in the H-BFR condition compared to all other conditions. However, there were no significant differences between conditions in VO 2 and MO 2 at equivalent powers. Compared to the N-BFR condition power output was lower by ~9% and ~21 % in the M-BFR and H-BFR condition respectively (fig 1) for fixed blood lactate concentration of 2 and 4mMol. Discussion: Using moderate and high levels of BFR during cycling exercise leads to substantial reductions (left shift) in power output at fixed blood lactate values. The reduced power was associated with increases in heart rate and RPE, at equivalent power outputs. However, measures of O 2 and MO 2 were not significantly different at comparable exercise intensities between the conditions. Conclusions: the decrease in attainable power output in BFR conditions appears predominately due to an increased reliance on anaerobic metabolism and an elevation in blood lactate concentration. Cardiovascular O2 delivery and extraction does not appear to be significantly affected by BFR. Â

Functional Threshold Power Is Not Equivalent to Lactate Parameters in Trained Cyclists.

Jeffries, O, Simmons, R, Patterson, SD, and Waldron, M. Functional threshold power is not equivalent to lactate parameters in trained cyclists. J Strength Cond Res 35(10): 2790-2794, 2021-Functional threshold power (FTP) is derived from a maximal self-paced 20-minute cycling time trial whereby the average power output is scaled by 95%. However, the physiological basis of the FTP concept is unclear. Therefore, we evaluated the relationship of FTP with a range of laboratory-based blood lactate parameters derived from a submaximal threshold test. Twenty competitive male cyclists completed a maximal 20-minute time trial and an incremental exercise test to establish a range of blood lactate parameters. Functional threshold power (266 ± 42 W) was strongly correlated (r = 0.88, p < 0.001) with the power output associated with a fixed blood lactate concentration 4.0 mmol·L-1 (LT4.0) (268 ± 30 W) and not significantly different (p > 0.05). While mean bias was 2.9 ± 24.6 W, there were large limits of agreement (LOA) between FTP and LT4.0 (-45 to 51 W). All other lactate parameters, lactate threshold (LT) (236 ± 32 W), individual anaerobic threshold (244 ± 33 W), and LT thresholds determined using the Dmax method (221 ± 25 W) and modified Dmax method (238 ± 32 W) were significantly different from FTP (p < 0.05). While FTP strongly correlated with LT4.0, the large LOA refutes any equivalence as a measure with physiological basis. Therefore, we would encourage athletes and coaches to use alternative field-based methods to predict cycling performance.

Characterizing the plasma metabolome during and following a maximal exercise cycling test.

Although complex in nature, a number of metabolites have been implicated in the onset of exercise-induced fatigue. The purpose of this study was to identify changes in the plasma metabolome and specifically, to identify candidate metabolites associated with the onset of fatigue during prolonged cycling. Eighteen healthy and recreationally active men (mean ± SD; age: 24.7 ± 4.8 yr; mass 67.1 ± 6.1 kg; body mass index: 22.8 ± 2.2; peak oxygen uptake: 40.9 ± 6.1 ml·kg-1·min-1) were recruited to this study. Participants performed a prolonged cycling time-to-exhaustion (TTE) test at an intensity corresponding to a fixed blood lactate concentration (3 mmol/l). Plasma samples collected at 10 min of exercise, before fatigue (last sample before fatigue <10 min before fatigue), immediately after fatigue (point of exhaustion), and 20 min after fatigue were assessed using a liquid chromatography-mass spectrometry-based metabolomic approach. Eighty metabolites were putatively identified, with 68 metabolites demonstrating a significant change during the cycling task (duration: ~80.9 ± 13.6 min). A clear multivariate structure in the data was revealed, with the first principal component (36% total variance) describing a continuous increase in metabolite concentration throughout the TTE trial and recovery, whereas the second principal component (14% total variance) showed an increase in metabolite concentration followed by a recovery trajectory, peaking at the point of fatigue. Six clusters of correlated metabolites demonstrating unique metabolite trajectories were identified, including significant separation in the metabolome between prefatigue and postfatigue time points. In accordance with our hypothesis, free-fatty acids and tryptophan contributed to differences in the plasma metabolome at fatigue.NEW & NOTEWORTHY Metabolites have long been implicated in the onset of fatigue. This study applied a metabolomic approach to track 80 plasma-borne metabolites during a cycle to fatigue task. Of these, 68 metabolites demonstrated significant change, with the plasma metabolome at fatigue being clearly distinguishable from other time points. Six unique clusters of metabolites were identified, and free fatty acids were strongly associated with fatigue onset therein lending support to the central fatigue hypothesis.

A "Blood Relationship" Between the Overlooked Minimum Lactate Equivalent and Maximal Lactate Steady State in Trained Runners. Back to the Old Days?

Maximal Lactate Steady State (MLSS) and Lactate Threshold (LT) are physiologically-related and fundamental concepts within the sports and exercise sciences. Literature supporting their relationship, however, is scarce. Among the recognized LTs, we were particularly interested in the disused “Minimum Lactate Equivalent” (LEmin), first described in the early 1980s. We hypothesized that velocity at LT, conceptually comprehended as in the old days (LEmin), could predict velocity at MLSS (VMLSS) more accurate than some other blood lactate-related thresholds (BLRTs) routinely used nowadays by many sport science practitioners. Thirteen male endurance-trained [VMLSS 15.0 ± 1.1 km·h−1; maximal oxygen uptake () 67.6 ± 4.1 ml·kg−1·min−1] homogeneous (coefficient of variation: ≈7%) runners conducted 1) a submaximal discontinuous incremental running test to determine several BLRTs followed by a maximal ramp incremental running test for determination, and 2) several (4–5) constant velocity running tests to determine VMLSS with a precision of 0.20 km·h−1. Determined BLRTs include LEmin and LEmin-related LEmin plus 1 (LEmin+1mM) and 1.5 mmol·L−1 (LEmin+1.5mM), along with well-established BLRTs such as conventionally-calculated LT, Dmax and fixed blood lactate concentration thresholds. LEmin did not differ from LT (P = 0.71; ES: 0.08) and was 27% lower than MLSS (P < 0.001; ES: 3.54). LEmin+1mM was not different from MLSS (P = 0.47; ES: 0.09). LEmin was the best predictor of VMLSS (r = 0.91; P < 0.001; SEE = 0.47 km·h−1), followed by LEmin+1mM (r = 0.86; P < 0.001; SEE = 0.58 km·h−1) and LEmin+1.5mM (r = 0.84; P < 0.001; SEE = 0.86 km·h−1). There was no statistical difference between MLSS and estimated MLSS using LEmin prediction formula (P = 0.99; ES: 0.001). Mean bias and limits of agreement were 0.00 ± 0.45 km·h−1 and ±0.89 km·h−1. Additionally, LEmin, LEmin+1mM and LEmin+1.5mM were the best predictors of (r = 0.72–0.79; P < 0.001). These results support LEmin, an objective submaximal overlooked and underused BLRT, to be one of the best single MLSS predictors in endurance trained runners. Our study advocates factors controlling LEmin to be shared, at least partly, with those controlling MLSS.

A Field-Based Cycling Test to Assess Predictors of Endurance Performance and Establishing Training Zones.

Sanders, D, Taylor, RJ, Myers, T, and Akubat, I. A field-based cycling test to assess predictors of endurance performance and establishing training zones. J Strength Cond Res 34(12): 3482-3488, 2020-This study evaluates the relationship between a field-based 8-minute time trial (8MTT) and physiological endurance variables assessed with an incremental laboratory test. Second, lactate thresholds assessed in the laboratory were compared with estimated functional threshold power (FTP) from the 8MTT. Nineteen well-trained road cyclists (aged 22 ± 2 years, height 185.9 ± 4.5 cm, body mass 72.8 ± 4.6 kg, V[Combining Dot Above]O2max 64 ± 4 ml·min·kg) participated. Linear regression revealed that mean 8MTT power output (PO) was strongly to very strongly related to PO at 4 mmol·L, PO at initial rise of 1.00 mmol·L, PO at Dmax and modified (mDmax) (r = 0.61-0.82). Mean 8MTT PO was largely to very largely different compared with PO at fixed blood lactate concentration of 2 mmol·L (ES = 3.20) and 4 mmol·L (ES = 1.90), PO at initial rise 1.00 mmol·L (ES = 2.33), PO at Dmax (ES = 3.47) and mDmax (ES = 1.79) but only trivially different from maximal PO (Wmax) (ES = 0.09). The 8MTT based estimated FTP was moderate to very largely different compared with PO at initial rise of 1 mmol·L (ES = 1.37), PO at Dmax (ES = 2.42), PO at mDmax (ES = 0.77) and PO at 4 mmol·L (ES = 0.83). Therefore, even though the 8MTT can be valuable as a performance test in cycling shown through its relationships with predictors of endurance performance, coaches should be cautious when using FTP and PO at laboratory-based thresholds interchangeably to inform training prescription.

On-field prediction vs monitoring of aerobic capacity markers using submaximal lactate and heart rate measures.

This study aimed to validate the use of a single blood lactate concentration measurement taken following a 5-minute running bout at 10km·h-1 (BLC10 ) and the speed associated with 90% of maximal heart rate (S90 ) to predict and monitor fixed blood lactate concentration (FBLC) thresholds in athletes. Three complementary studies were undertaken. Study I: A cross-sectional study examining the associations of BLC10 and S90 with running speeds at FBLC of 3 (S3mM) and 4mmol·L-1 (S4mM) in 100 athletes. Study II: A cross-validation study assessing the predictive capacity of BLC10 and S90 to estimate FBLC thresholds in real practice. Study III: A longitudinal study examining whether training-induced changes in FBLC thresholds could be monitored using BLC10 and S90 in 80 athletes tested before and after an intensified training period. Study I: BLC10 (r=-.87 to -.89) and S90 (r=.73-.79) were very largely (P<.001) related to FBLC thresholds. Study II: Predictive models yielded robust correlations between estimated and measured FBLC thresholds (r=.75-.91; P<.001). The limits of agreements, however, revealed that prediction of FBLC thresholds could be biased up to 9%-15%. Study III: BLC10 was very largely related to training-induced changes in FBLC thresholds (r=-.72 to -.76; P<.001). Increases in S90 were associated with improvements in FBLC thresholds, but decreases in S90 led to unclear changes in FBLC thresholds. This study supports the use of BLC10 as a simple, low-cost, non-fatiguing, and time-efficient functional variable to monitor, but not predict, FBLC thresholds in athletes. The present results also question the use of S90 to detect declines in endurance performance.

Validity of a single lactate measure to predict fixed lactate thresholds in athletes

ABSTRACTThis study aimed to validate the use of a single blood lactate concentration measure taken following a 12 km h−1 running stage (BLC12) to predict and monitor fixed blood lactate concentration (FBLC) thresholds. Three complementary studies were undertaken. Study I: the relationships between BLC12 and the running speeds at FBLC of 3 mmol L−1 (S3mM) and 4 mmol L−1 (S4mM) measured during a multistage running field test were examined in 136 elite athletes. Study II: data from 30 athletes tested one year apart were used to test the predictive capacity of the equations obtained in Study I. Study III: 80 athletes were tested before and after an intensified training period to examine whether training-induced changes in FBLC thresholds could be predicted and monitored by BLC12. Study I: BLC12 was significantly (P < 0.001) and inversely related to S3mM (R2 = 0.89) and S4mM (R2 = 0.95). Study II: prediction models yielded robust correlations between the estimated and measured FBLC thresholds (r = 0.94–0.99; P < 0.001). Study III: estimated changes predicted actual training-induced changes in FBLC thresholds (r = 0.81–0.91; P < 0.001). This study gives empirical support to use a single lactate measure during a sub-maximal running field test as a simple, low-cost and practical alternative to FBLC thresholds in athletes.

Influence of electrically assisted cycling on physiological parameters in untrained subjects

Electrically assisted bicycles (EAB) as a form of transport not only offer the potential to reduce energy use and environmental impact but could also be an effective way of encouraging active living. The purpose of this study is to assess the influence of physical active commuting to work using an EAB, on physiological parameters in 20 untrained men and women. Tests were performed at three different time points over a 10-week period, including four weeks of passive (control period) and six weeks of active commuting (intervention period). ANOVA for repeated measures was used to test differences between the testing series for the most important physiological parameters: Pmax·kg−1, V˙O2peak·kg−1, fixed blood lactate concentration (2, 4 mmol·l−1). The subjects performed over a 6-week period a mean total cycling distance of 405.1±156.0 km with a weekly frequency of 4.1±1.7 days·week−1 for men and 246.0±116.3 km with a frequency of 2.9±1.0 days·week−1 for women. Pmax·kg−1 significantly increased in men and women after 6 weeks of active commuting. Power output at 2 mmol·l−1 significantly increased in women (P=0.001) but not in men (P=0.0604). Power output at 4 mmol·l−1 significantly increased for men and women. V˙O2peak·kg−1 did not differ. With respect to the study limitations, it is concluded that cycling to work on an EAB was effective in increasing the maximal power output and power output at 4 mmol·l−1 in these untrained subjects. Cycling on an EAB seems to be a promising tool as a health enhancing physical activity, for those who will benefit the most in terms of health related fitness, namely the physically inactive, unfit and older people.

Seasonal Aerobic Performance Variations in Elite Soccer Players

The purpose of this study was to examine the seasonal changes in body composition and aerobic performance in elite soccer players. Twelve elite professional soccer players (aged 25 6 5 years, weight 75.7 6 5.3 kg, height 1.79 6 0.06 m) were measured for body fat (%), maximum oxygen consumption (VO2max), running velocity at VO2max (VO2max), running velocity at a fixed blood lactate concentration of 4 mmol · L21 (v-4 mM) at the start of the preseason period, at the beginning of the competitive period, and at midseason. VO2max, v-4 mM, and vVO2max increased significantly (p , 0.05) by 4.5, 10.5, and 7.8,respectively, after the preseason period. Thereafter, the aerobic performance parameters remained relatively constant, with no significant changes throughout the competitive period. The results of this study suggest that moderate improvements were observed in VO2max, and the %VO2max at 4 v-4 mM, whereas higher improvements were observed in VO2max and v-4 mmol · L21 after the preseason training period. On the other hand, during the competitive period, aerobic performance remained unchanged.In addition, this study suggests that heart rate, lactate, vVO2, and VO2max are useful and practical predictors that help monitor aerobic performance changes during a soccer season.

Limiar anaeróbio em corrida e natação para ratos: determinação utilizando dois métodos matemáticos

The study aimed to determine the anaerobic threshold (AT) with incremental test in swimming and running rats, using two mathematical methods for analysis: fixed blood lactate concentration and visual inspection of inflection point preceded by bi-segmental linear regression. Swimming (n=19) and running rats (n=29) were used. The incremental test was composed by 5 minutes of exercise with blood collection after loads for lactate concentration determination. The AT was determined by fixed lactate concentration (4.0; 4.5;5.0; 5.0mmol/L) and the visual inspection of inflection point of the lactate curve, preceded by intersection of the bi-segmental linear regression. The AT intensities were compared by one-way Anova. In swimming rats the best analysis for AT determination seems to be fixed blood lactate in concentrations (5.0 and 5.5mmol/L, load=4.2±0.1%bw). In treadmill running, the bi-segmental linear regression was possible with 67.2% of animals (AT=21.1±0.9 m/min) and this method seems to be the adequate for running rats.

Physiological correlates of 2-mile run performance as determined using a novel on-demand treadmill

The purpose of this study was to assess the reproducibility of an on-demand motorised treadmill to measure 2-mile (3.2 km) race performance and to examine the physiological variables that best predict this free-running performance in active men. Twelve men (mean (SD): age, 28 (9) years; stature, 1.79 (0.05) m; body mass, 72 (9) kg) completed the study in which maximum oxygen uptake (VO2 max), running economy, and running speedin the abstract section. They appear in the rest of the paper.), running economy, and running speed at VO2 max (vVO2 max), lactate threshold (vLT), and 4 mmol.L-1 fixed blood lactate concentration (v4) were measured. Subsequently, the maximal lactate steady state (MLSS) was identified using a series of 30-min treadmill runs. Finally, each participant completed a 2-mile running performance trial on 2 separate occasions, using an on-demand treadmill that adjusts belt speed according to the participant's position on the moving belt. The average 2-mile run speed was 15.7 (SD, 1.9) km.h-1, with small individual differences between repeat-performance trials (intraclass correlation coefficient = 0.99, 95% CI 0.953 to 0.996; standard error of measurement as coefficient of variation = 1.5%, 95% CI 1.0% to 2.5%). Bivariate regression analyses identified VO2 max, vVO2 max, VO2 (mL.kg-1.min-1) at MLSS, vLT, v4, and velocity at MLSS (vMLSS) as the strongest individual predictor variables (r2 = 0.69 to 0.87; standard error of the estimate = 1.08 to 0.72 km.h-1) for 2-mile running performance. The vLT and vMLSS explained 85% and 87% of the variance in running performance, respectively, suggesting that there is considerable shared variance between these parameters. In conclusion, the on-demand treadmill system provided a reliable measure of distance running performance. Both vLT and vMLSS were strong predictors of 2-mile running performance, with vMLSS explaining marginally more of the variance.

Non-invasive detection of the anaerobic threshold by a neural network model of the heart rate—work rate relationship

The heart rates (HRs) indicating the anaerobic threshold, which corresponds to a fixed blood lactate concentration of 4mmol/l (heart rate at the onset of blood lactate accumulation (HR-OBLA)); are predicted on the basis of the heart rate—work rate relationship during exercise performance. The predictor is a multi-layer perceptron (MLP). For training and testing, 225 male soccer players (mean age, 21.6±4.5 years) performed an incremental running test on a treadmill with 3-min runs and 30-s blood sampling sessions for lactate assessment. In addition to the treadmill test data, the ages, masses, heights, body mass indices, and playing positions of half of the subjects ( n=113) were used to train the MLP and the remaining 112 were used for external validation. The results showed that the HR values recorded in the last stages before exhaustion were strong predictors of HR-OBLA ( r=0.875; standard error of estimates, 4.17). Inclusion of other parameters did not improve the prediction rate. Although additional work is needed to generalize the method to training prescription, results suggest that a neural network is a promising non-invasive tool for accurately estimating the HR-OBLA from exercise test data.

Acute exercise performed close to the anaerobic threshold improves cognitive performance in elderly females

The objective of the present study was to compare the effect of acute exercise performed at different intensities in relation to the anaerobic threshold (AT) on abilities requiring control of executive functions or alertness in physically active elderly females. Forty-eight physically active elderly females (63.8 +/- 4.6 years old) were assigned to one of four groups by drawing lots: control group without exercise or trial groups with exercise performed at 60, 90, or 110% of AT (watts) and submitted to 5 cognitive tests before and after exercise. Following cognitive pretesting, an incremental cycle ergometer test was conducted to determine AT using a fixed blood lactate concentration of 3.5 mmol/L as cutoff. Acute exercise executed at 90% of AT resulted in significant (P < 0.05, ANOVA) improvement in the performance of executive functions when compared to control in 3 of 5 tests (verbal fluency, Tower of Hanoi test (number of movements), and Trail Making test B). Exercising at 60% of AT did not improve results of any tests for executive functions, whereas exercise executed at 110% of AT only improved the performance in one of these tests (verbal fluency) compared to control. Women from all trial groups exhibited a remarkable reduction in the Simple Response Time (alertness) test (P = 0.001). Thus, physical exercise performed close to AT is more effective to improve cognitive processing of older women even if conducted acutely, and using a customized exercise prescription based on the anaerobic threshold should optimize the beneficial effects.

Influence of exercise mode and maximal lactate-steady-state concentration on the validity of OBLA to predict maximal lactate-steady-state in active individuals

The aim of this study was to analyze the effects of exercise mode on the validity of onset of blood lactate accumulation (OBLA-3.5-mM fixed blood lactate concentration) to predict the work-rate at maximal lactate steady state (MLSS(work-rate)). Eleven recreationally active males (21.3+/-2.9 years, 72.8+/-6.7kg, 1.78+/-0.1m) performed randomly incremental tests to determine OBLA (stage duration of 3min), and 2 to 4 constants work-rate exercise tests to directly determine maximal lactate steady state parameters on a cycle-ergometer and treadmill. For both exercise modes, the OBLA was significantly correlated to MLSS(work-rate), (cycling: r=0.81 p=0.002; running: r=0.94, p<0.001). OBLA (156.2+/-41.3W) was lower than MLSS(work-rate) (179.6+/-26.4W) during cycling exercise (p=0.007). However, for running exercise, there was no difference between OBLA (3.2+/-0.6ms(-1)) and MLSS(work-rate) (3.1+/-0.4ms(-1)). The difference between OBLA and MLSS(work-rate) on the cycle-ergometer (r=0.86; p<0.001) and treadmill (r=0.64; p=0.048) was significantly related to the specific MLSS. We can conclude that the validity of OBLA on predicting MLSS(work-rate) is dependent on exercise mode and that its disagreement is related to individual variations in MLSS.

Using a general purpose spreadsheet software package to estimate exponential plus constant model fits for blood lactate concentration versus work rate data

The objective of this analysis was to evaluate the accuracy of a standard spreadsheet software package to estimate best-fit parameters for an exponential plus constant model (y=a+b.e cx ) applied to blood lactate concentration versus work rate data. During an incremental cycle test, blood lactate concentrations were measured in six endurance-trained athletes. A spreadsheet (Microsoft ® Excel) and a dedicated curvefitting software programme (GraphPad Prism ® ) were used to obtain model coefficients, model fit parameters, interpolated work rate at a fixed blood lactate concentration (WR 4mmol/l ) and work rate at a curve gradient of 1 mmol/l per watt (WR dy/dx=1 ). Model coefficients and model fit parameters were identical to the sixth decimal place for four subjects and differed by ≤0.000006 in two subjects. WR 4mmol/l differed by dy/dx=1 differed by 0.0018 watts in only one subject. These findings suggest that a general purpose spreadsheet software package can be used by sport and exercise physiologists to accurately determine model coefficients, model fit parameters, WR 4mmol/l and WR dy/dx=1 . South African Journal for Research in Sport, Physical Education and Recreation Vol. 28(2) 2006: 27-37