Heart Rate Deflection Research Articles

A comparison of different heart rate deflection methods to predict the anaerobic threshold

There is perhaps no greater controversy in exercise physiology than the validity, or lack thereof, of the heart rate breakpoint theory in general, and the Conconi test in particular, in assessing the anaerobic threshold. Three heart rate breakpoint methods have been proposed as methods of detecting the anaerobic threshold have appeared in the literature: (1) a breakpoint in linearity of the heart rate–work rate relationship (heart rate breakpoint); (2) a log function curve of the heart rate–work rate relationship (log function); and (3) a combination of linear regression and logarithmic function of the heart rate–work rate relationship (log-linear). The main aim of this study was to assess the validity of these methods compared with that of gas analysis assessment of the anaerobic threshold. This was a descriptive study of 115 endurance athletes undergoing simultaneous gas analysis and heart rate determination during incremental exercise to exhaustion. The participants were 115 competitive cyclists and/or triathletes (71 males: mean age 38.5 years, s=6.2; 44 females: mean age 37.8 years, s=5.1). Incremental exercise testing to exhaustion was performed on an electrically braked cycle ergometer, commencing at 25 W and increasing by 25 W · min−1 to volitional fatigue. Heart rate was recorded each minute and at exhaustion. Gas analysis was performed using breath-by-breath analysis with 10-s averaging. The anaerobic threshold based on ventilatory parameters was used as the criterion test. Compared with the criterion threshold, no significant differences were observed for the heart rate breakpoint (t=1.12, P=0.268) or log function (t=0.0, P=0.998) methods. However, the log-linear method (t=2.25, P=0.026) significantly overestimated the anaerobic threshold. Although two of the three heart rate methods were validated in this study, the relatively large total errors for these methods (13.7 beats · min−1 for heart rate breakpoint, 12.5 beats · min−1 for log function, and 14.3 beats · min−1 for log-linear) indicate that they would have little practical value.

Determination of the intensity of a power jump session by means of heart rate monitoring

A Power Jump (PJ) session is considered to be a safe and easy class that also involves intermittent exercises that prolong the time to exhaustion. However, there is not enough information about this subject in the literature. The purpose of this study was to determine the intensity of a PJ session by means of heart rate (HR) monitoring. Eleven physically active females participated in the study (age: 21.7 ± 1.9 years; body mass: 59.3 ± 4.8 kg; height: 162.6 ± 5.6 cm; percentage body fat: 22.6 ± 3.2 %). Participants were asked to perform an incremental test (IT), in order to obtain values for oxygen uptake (VO2), maximal heart rate (HRmax), heart rate deflection point (HRDP) and energy expenditure (EE). The HR of the subjects was monitored during a special type of Power Jump session called “mix nine” on two different occasions. According to the HRDP values, physiological domains could be divided into three exercise intensity classes: moderate, heavy and severe. Descriptive statistics were adopted (mean ± SD). Student’s t test was used to compare HR and EE between PJ1 and PJ2. For comparisons between domains, two-way ANOVA and the Scheffe test were used. The level of significance was set at p<0.05. Mean HRmax obtained during the IT was 195±10bpm. The velocities, HR and %HRmax corresponding to HRDP and 80% of HRDP were 10.1±0.95km.h-1, 178±7bpm and 91.7±4.0%; and 8.1±0.76km.h-1, 143±5bpm and 73.4±3.2%, respectively. Values for HRmean and EE were significantly different when PJ1 (161±11bpm, 386±58.2kcal) and PJ2 (156±10bpm, 355.1±53.8kcal) were compared. The times spent in each exercise intensity domain were: heavy 51±14.5%; severe 27±19.7% and moderate 23±8.7%. These results show that the subjects spent most of the time in the heavy exercise domain which, in turn, appears to be the most indicated for improving aerobic capacity.

Rebuttal from Drs. Warburton and Gledhill

Rebuttal from Drs. Warburton and Gledhill

Validity of the Modified Conconi Running Test

The aim of this study was to assess the validity of a fast ramp treadmill protocol for determination of the heart rate deflection point (HR (dp)) and speed of deflection (S (dp)) in trained runners. Fifty-one trained male runners performed a standard (T (stand); speed increase 1 km . h (-1) every 60 s) and a fast (T (fast); speed increase 1 km . h (-1) every 30 s) incremental treadmill test until volitional exhaustion. Heart rate was continuously recorded, and the HR (dp) was estimated after data averaging as the point of deflection in the linear speed/HR relationship. The HR (dp) and S (dp) recorded in T (fast) were compared with the corresponding values obtained in T (stand) by examining the Student's T-test, correlation coefficient (r), and limits of agreement (LoA). The HR (dp) recorded during standard and fast treadmill protocol were highly correlated (r = 0.92, p < 0.001) and similar to each other (p = 0.79). In contrast, S (dp) was highly correlated (r = 0.91, p < 0.001), but increased significantly with the faster ramp function (p < 0.001). No evidence of systematic bias was evident in the HR (dp) (95 % LoA of 0.2 +/- 7.3 bpm), while a uniform, systematic bias was evident for S (dp) in the T (fast) (95 % LoA of 1.6 +/- 1.5 km x h (-1)). We conclude that a fast ramp treadmill protocol (speed increase 1 km x h (-1) every 30 s) may be used for determination of the HR (dp) in trained runners, while S (dp) is protocol dependent and caution is warranted regarding its practical applicability.

Utility of the Conconi's Heart Rate Deflection to Monitor the Intensity of Aerobic Training

The Conconi's heart-rate deflection point (HRd) in the heart rate (HR)/speed curve is often used to set aerobic training loads. Training could either be set in percentage running speed or HR at HRd. In order to establish the limits and usefulness of various aerobic-training modalities for intermediate athletic level (physical-education students), acute responses were analyzed while running for a typical 40-minute training session. Speed, HR, lactate, and cortisol were thus recorded during training at 90 and 100% of running speed (RS: n = 14) and HR (HR: n = 16) at HRd (90% running speed [RS90], 100% running speed [RS100], 90% HR [HR90], and 100% HR [HR100]). During constant HR training, RS decreases while HR drifts upward during constant RS training. Half of the subjects can not finish the 40-minute RS100 session. For HR90, RS90, HR100, and RS100, average intensities are 67, 69, 74.9, and 77% maximal aerobic speed (multistage test), respectively. This study indicates that (1) training at HR100 and RS100 is more appropriate to improve high-intensity metabolic capacities (increased cortisol and lactate) while RS100 is too difficult to be maintained for 40 minutes for subjects at that level at least, (2) training at HR90, however, is better to improve endurance and capacity to do a large amount of work considering cortisol and lactate homeostasis, and (3) training at a constant HR using a HR monitor is a good method to control the intensity of the training with subjects not used to pacing themselves with the split-time approach.

Relationship between laboratory-measured variables and heart rate during an ultra-endurance triathlon

The aim of the present study was to examine the relationship between the performance heart rate during an ultra-endurance triathlon and the heart rate corresponding to several demarcation points measured during laboratory-based progressive cycle ergometry and treadmill running. Less than one month before an ultra-endurance triathlon, 21 well-trained ultra-endurance triathletes (mean ± s: age 35 ± 6 years, height 1.77 ± 0.05 m, mass 74.0 ± 6.9 kg, = 4.75 ± 0.42 l · min−1) performed progressive exercise tests of cycle ergometry and treadmill running for the determination of peak oxygen uptake ( ), heart rate corresponding to the first and second ventilatory thresholds, as well as the heart rate deflection point. Portable telemetry units recorded heart rate at 60 s increments throughout the ultra-endurance triathlon. Heart rate during the cycle and run phases of the ultra-endurance triathlon (148 ± 9 and 143 ± 13 beats · min−1 respectively) were significantly (P < 0.05) less than the second ventilatory thresholds (160 ± 13 and 165 ± 14 beats · min−1 respectively) and heart rate deflection points (170 ± 13 and 179 ± 9 beats · min−1 respectively). However, mean heart rate during the cycle and run phases of the ultra-endurance triathlon were significantly related to (r = 0.76 and 0.66; P < 0.01), and not significantly different from, the first ventilatory thresholds (146 ± 12 and 148 ± 15 beats · min−1 respectively). Furthermore, the difference between heart rate during the cycle phase of the ultra-endurance triathlon and heart rate at the first ventilatory threshold was related to marathon run time (r = 0.61; P < 0.01) and overall ultra-endurance triathlon time (r = 0.45; P < 0.05). The results suggest that triathletes perform the cycle and run phases of the ultra-endurance triathlon at an exercise intensity near their first ventilatory threshold.

Protocol for the Conconi Test and Determination of the Heart Rate Deflection Point

Recently Ozcelik and Kelestimur (2004) have assessed the validity of the heart rate deflection point in the power output-heart rate relationship (Conconi test) for estimating the anaerobic threshold in different experimental conditions (normoxia and hypoxia). In their study, the tests were performed with an electromagnetically braked cycle ergometer at constant cadence with increments in power output obtained by increasing the pedalling resistance.

Heart rate deflection point as a strategy to defend stroke volume during incremental exercise

The purpose of this study was to examine whether the heart rate (HR) deflection point (HRDP) in the HR-power relationship is concomitant with the maximal stroke volume (SV(max)) value achievement in endurance-trained subjects. Twenty-two international male cyclists (30.3 +/- 7.3 yr, 179.7 +/- 7.2 cm, 71.3 +/- 5.5 kg) undertook a graded cycling exercise (50 W every 3 min) in the upright position. Thoracic impedance was used to measure continuously the HR and stroke volume (SV) values. The HRDP was estimated by the third-order curvilinear regression method. As a result, 72.7% of the subjects (HRDP group, n = 16) presented a break point in their HR-work rate curve at 89.9 +/- 2.8% of their maximal HR value. The SV value increased until 78.0 +/- 9.3% of the power associated with maximal O(2) uptake (Vo(2 max)) in the HRDP group, whereas it increased until 94.4 +/- 8.6% of the power associated with Vo(2 max) in six other subjects (no-HRDP group, P = 0.004). Neither SV(max) (ml/beat or ml.beat(-1).m(-2)) nor Vo(2 max) (ml/min or ml.kg(-1).min(-1)) were different between both groups. However, SV significantly decreased before exhaustion in the HRDP group (153 +/- 44 vs. 144 +/- 40 ml/beat, P = 0.005). In the HRDP group, 62% of the variance in the power associated with the SV(max) could also be predicted by the power output at which HRDP appeared. In conclusion, in well-trained subjects, the power associated with the SV(max)-HRDP relationship supposed that the HR deflection coincided with the optimal cardiac work for which SV(max) was attained.

Validity of the Heart Rate Deflection Point As a Predictor of Lactate Threshold Concepts During Cycling

Validity of the Heart Rate Deflection Point As a Predictor of Lactate Threshold Concepts During Cycling

Effects of Acute Hypoxia on the Determination of Anaerobic Threshold Using the Heart Rate-Work Rate Relationships during Incremental Exercise Tests.

Anaerobic threshold which describes the onset of systematic increase in blood lactate concentration is a widely used concept in clinical and sports medicine. A deflection point between heart rate-work rate has been introduced to determine the anaerobic threshold non-invasively. However, some researchers have consistently reported a heart rate deflection at higher work rates, while others have not. The present study was designed to investigate whether the heart rate deflection point accurately predicts the anaerobic threshold under the condition of acute hypoxia. Eight untrained males performed two incremental exercise tests using an electromagnetically braked cycle ergometer: one breathing room air and one breathing 12 % O2. The anaerobic threshold was estimated using the V-slope method and determined from the increase in blood lactate and the decrease in standard bicarbonate concentration. This threshold was also estimated by in the heart rate-work rate relationship. Not all subjects exhibited a heart rate deflection. Only two subjects in the control and four subjects in the hypoxia groups showed a heart rate deflection. Additionally, the heart rate deflection point overestimated the anaerobic threshold. In conclusion, the heart rate deflection point was not an accurate predictor of anaerobic threshold and acute hypoxia did not systematically affect the heart rate-work rate relationships.

The Relationship of the Heart Rate Deflection Point to the Ventilatory Threshold in Trained Cyclists

The Relationship of the Heart Rate Deflection Point to the Ventilatory Threshold in Trained Cyclists

Lactic acidosis, potassium, and the heart rate deflection point in professional road cyclists

Objective: To determine the influence of lactic acidosis, the Bohr effect, and exercise induced hyperkalaemia on the occurrence of the heart rate deflection point (HRDP) in elite (professional) cyclists. Methods:...

Ventilatory Threshold in Children: A Review

Ventilatory threshold (VT) is an important index of aerobic exercise function. The non-invasive nature of assessing VT and the fact that VT can be determined without obtaining a maximal exertion makes it broadly appealing to study in both healthy and diseased populations. Much of the understanding of the physiological and biochemical events underlying the occurrence and significance of VT is based on research involving adults. Several conclusions can be made from the studies which have examined VT in children. First, VT can be determined in a reliable manner. Second, heart rate deflection has been used as an alternative method to estimate VT and, based on limited information, appears to have reasonable accuracy. Third, although there is some evidence suggesting that VT (relative to maximal oxygen uptake [V̇O2max]) declines with maturation, the evidence is not overwhelming and it is based primarily on cross-sectional comparisons. Fourth, endurance training will increase VT in children to a greater extent than the increase in V̇O2max. Lastly, the physiological significance of VT and the metabolic consequences when exercise intensities exceeds VT are not well understood in children and are fruitful areas of research.

The Relationship of the Heart Rate Deflection Point to the Ventilatory Threshold in Trained Cyclists

The purpose of this study was to assess the relationship of the heart rate deflection point (HRDP) to the ventilatory threshold (VT) in trained cyclists. Twenty-one endurance-trained cyclists (mean +/- SD: Vo(2)max = 67.6 +/- 4.7 ml x kg x min(-1)) completed a maximal cycle ergometer test of volitional fatigue using a ramped protocol. Ventilatory variables (Ve, Vo(2), Vco(2)) and power were measured online with averages reported every 20 seconds. Heart rate (HR) was recorded every 20 seconds using a Polar monitor. VT was calculated using the excess CO(2) elimination curve. The first derivative of a logistic growth curve fit to the HR-power data produced the HRDP. No significant differences (p > 0.01) existed between HR values at HRDP (171.7 +/- 9.6 b x min(-1)) and VT (169.8 +/- 9.9 b x min(-1)) or between Vo(2) values at HRDP (53.6 +/- 4.2 ml x kg x min(-1)) and VT (52.2 +/- 4.8 ml x kg x min(-1)). But power values at HRDP (318.7 +/- 30.7 W) were significantly different (p < 0.01) from those at VT (334.8 +/- 36.7 W). There were significant relationships between HRDP and VT for the physiological variables of HR (r = 0.92, p < 0.001), Vo(2) (r = 0.72, p < 0.001), and power (r = 0.77, p < 0.001). These findings indicate that HR and Vo(2) at HRDP are not significantly different from the values at VT in trained cyclists. HR values derived from HRDP may be used to set parameters for training intensity. Variability in the speed/power-HRDP relationship across detrained/trained states may be used to evaluate training programs.

A review of the concept of the heart rate deflection point.

The heart rate deflection point (HRDP) is a downward or upward change from the linear HR-work relationship evinced during progressive incremental exercise testing. The HRDP is reported to be coincident with the anaerobic threshold. In 1982, Conconi and colleagues suggested that this phenomenon could be used as a noninvasive method to assess the anaerobic threshold. These researchers developed a field test to assess the HRDP, which has become popularised as the 'Conconi test'. Concepts used to define and assess the anaerobic threshold as well as methodological procedures used to determine the HRDP are diverse in the literature and have contributed to controversy surrounding the HRDP concept. Although the HRDP may be assessed in either field or laboratory settings, the degree of HR deflection is highly dependent upon the type of protocol used. The validity of HRDP to assess the anaerobic threshold is uncertain, although a high degree of relationship exists between HRDP and the second lactate turnpoint. The HRDP appears to be reliable when a positive identification is made; however, not all studies report 100% reproducibility. Although the physiological mechanisms explaining the HRDP are unresolved, a relationship exists between the degree and direction of HRDP and left ventricular function. The HRDP has potential to be used for training regulation purposes. Clinically, it may be incorporated to set exercise intensity parameters for cardiac rehabilitation.

Heart dimensions may influence the occurrence of the heart rate deflection point in highly trained cyclists.

OBJECTIVES: To determine whether the heart rate (HR) response to exercise in 21 highly trained cyclists (mean (SD) age 25 (3) years) was related to their heart dimensions. METHODS: Before...

Validity of the heart rate deflection point as a predictor of lactate threshold during running.

During an incremental run test, some researchers consistently observe a heart rate (HR) deflection at higher speeds, but others do not. The present study was designed to investigate whether differences in test protocols could explain the discrepancy. Additionally, we sought to determine whether the HR deflection point accurately predicts lactate threshold (LT). Eight trained runners performed four tests each: 1) a treadmill test for maximal O(2) uptake, 2) a Conconi test on a 400-m track with speeds increasing approximately 0.5 km/h every 200 m, 3) a continuous treadmill run with speeds increasing 0.5 km/h every minute, and 4) a continuous LT treadmill test in which 3-min stages were used. All subjects demonstrated an HR deflection on the track, but only one-half of the subjects showed an HR deflection on the treadmill. On the track the shortening of stages with increasing speeds contributed to a loss of linearity in the speed-HR relationship. Additionally, the HR deflection point overestimated the LT when a continuous treadmill LT protocol was used. In conclusion, the HR deflection point was not an accurate predictor of LT in the present study.

Comparison of a Mathematical Model to Predict 10-km Performance From the Conconi Test and Ventilatory Threshold Measurements

The purpose of this study was to validate a mathematical model (MM) that evaluates the Conconi test and predicts 10-km race time. In addition, the relationship between ventilatory threshold (Tvent) determined from a laboratory test and heart rate deflection (HRd) from the Conconi test were examined. Seventeen trained runners performed the Conconi test, and performance times were predicted using a MM based on a logistics function. A correlational analysis indicated a highly significant relationship (r = .98, p < .01) between MM predicted time and actual time. Significant relationships were found between velocity at Tvent and HRd (r = .95, p < .01), and predicted times from each method (r = .96, p < .01). Heart rates from Tvent and HRd were also related (r = .79, p < .01). These results suggest that a MM of the Conconi test is a valid method of predicting 10-km performance and is closely related to traditional laboratory measures.

Possible effect of the supplementation of branched chain aminoacids, aspartate and asparagine on anaerobic threshold

Recentemente o conceito “Limiar Anacróbio” tem sido muito criticado. As principais críticas repousam sobre os mecanismos considerados para o aumento da concentração de laclato sangüíneo, hipóxia muscular principalmente, c sobre a suposta relação de causa-c-cfeito entre os limiares mctabólico e ventilatório. Apesar de criticado, o conceito Limiar Anacróbio encontrou muitas aplicações, c por esta razão, vários estudos foram realizados para facilitar a sua determinação não invasivamente, a partir de parâmetros ventilatórios c da dcílexão da curva de freqüência cardíaca. Recentemente o uso de aminoácidos tem se difundido largamente entre os praticantes de atividades motoras, tornando-se objeto de estudo para vários pesquisadores. Foi proposto que a suplementação de aminoácidos de cadeia ramificada, aspartalo c asparagina promove aumento da resistência ao esforço físico prolongado, em decorrência do aumento do conteúdo de glicogênio muscular c síntese de oxaloacetato para manutenção da atividade do ciclo de Krebs c do própio metabolismo oxidativo. Com isto o transporte de glicose para o interior da célula muscular diminui, retardando a dcplcção de glicogênio muscular e a acidose metabólica, causas evidentes de fadiga. Em conseqüência, a oxidação de AGLs durante o exercício contínuo moderado aumenta, retardando o acúmulo de lactato sangüíneo c muscular. Isto retardaria o estímulo mctabólico para o processo de tamponamento pelo H C 03' c a conseqüente compensação venlilalória para C 0 2, podendo dissociar os limiares mctabólico c ventilatório. A dissociação dos limiares reforçaria as críticas sobre o conceito Limiar Anacróbio c poderia, inclusive, prejudicar a sua identificação através de outros métodos, como por exemplo, a dcílexão da curva de freqüência cardíaca

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

In 1992 Conconi et al. (20) presented an indirect and noninvasive method for the determination of anaerobic threshold (AnT) in an incremental field test for runners. This noninvasive method for the determination of anaerobic threshold is dependent on the occurrence of a deflection of the heart rate performance curve (HRPC). The aim of our study was to evaluate the degree and direction of the deflection of the HRPC and the relationship of the heart rate threshold (HRT) to the lactate turn point in a group of 227 healthy young subjects (age: 23 +/- 4 yr). The subjects were divided into three groups by means of second degree polynomial fitting (GI: regular deflection, kHR > 0.1; G II: no deflection, 0 < kHR < 0.1; G II: inverse deflection, k < -0.1). No significant differences between the groups were found in the anthropometric data or in the power output and the blood lactate concentration at both the first (LTP1) and second (LTP2) lactate turn points and at maximum performance (Pmax). Using the method of Conconi et al. (20), 85.9% of the subjects showed a "regular" deflection, 6.2% showed no deflection at all, and 7.9% showed even an inverted deflection of the HRPC. An HRT could be obtained in both G I and G III, and power output at HRT was not significantly different in comparison to that at the LTP2. No HRT could be assessed in G II. The heart rate at HRT and the LTP2 were significantly lower in G III compared with G I. The phenomenon of heart rate break point may be attractive in training regulation, but its application is limited because a heart rate deflection cannot be found even in young subjects in some cases.