Q for Rob - Linear limit HR

[kieran]

Hi Rob, on your outputs what is linear limit HR? and does it have any relation to max HR?

[Robh]

Hi Kieran,

After I've done the LBP test I use the FaCT software to find the lower linear limit & upper linear limit. This is found by looking at the blue points and creating a line which has as many points as as possible close to this blue perfromance line.

1. Lower linear limit (LLL) is the lowest heart rate you should have to still stress your cardiovascular system or the highest you should go if you are sick. It is very often identical with the Polar lower own zone or with HRV at 4ms.

During the test I also use the HRV function to find this point for the start of the Bi-STF zone. Sometimes it's close to LLL.

2. What is HRV (also known as RLX) :-

Hear rate variability is a measure of relative stress level as the cardiac system responds to a load getting signals from the autonomic nervous system - a measurement of training status. Little or no variability during a workout indicates a higher level of stress on the body (look at each person's recording sheet for reference).

When the variation is larger, from beat to beat, there is a general indication of a relatively healthy cardiovascular system or little stress as you see at the beginning of the test. It is truly a second window into what the heart is doing."

3. Upper linear limit (ULL) is the highest heart rate you should go in a hard race to still have an optimal performance and where the HR has optimal stroke volume.

[Robh]

Copied from FaCT forum :-

ULL interpretation done in France.

Heart rate deflection point as a strategy to defend stroke volume during incremental exercise
Pierre-Marie Lepretre,1 Carl Foster,2 Jean-Pierre Koralsztein,3 and Veronique L. Billat1,3

1Laboratoire d'Etude de la Physiologie de l'Exercice, Department of Sciences and Technology in Sports and Physical Activities, University of Evry Val d'Essonne, Evry, France 2University of Wisconsin-La Crosse, La Crosse, Wisconsin; and 3Sport Medicine Center of the Caisse Centrale d'Activités Sociales, Paris, France

Submitted 4 August 2004 ; accepted in final form 29 November 2004

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 (SVmax) 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 O2 uptake (O2 max) in the HRDP group, whereas it increased until 94.4 ± 8.6% of the power associated with O2 max in six other subjects (no-HRDP group, P = 0.004). Neither SVmax (ml/beat or ml·beat–1·m–2) nor O2 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 SVmax could also be predicted by the power output at which HRDP appeared. In conclusion, in well-trained subjects, the power associated with the SVmax-HRDP relationship supposed that the HR deflection coincided with the optimal cardiac work for which SVmax was attained.

physical work curve break point; left ventricular ejection fraction; cycling graded test

THE RESPONSE OF HEART RATE (HR) to incremental exercise is not always linear (5, 6) but shows a break point in the HR-physical work curve, the so-called HR deflection point (HRDP). Conconi et al. (8) reported that the intensity of the passage from the linear to the curvilinear phase in the HR-physical work curve coincided with the beginning of a sharp accumulation of blood lactate. The identification of the HRDP could be associated with a noninvasive determination of the anaerobic threshold (34). However, Conconi et al. supported a metabolic interpretation of the appearance of the break point in the HR-intensity relationship while lacking the interaction between the increase in the stroke volume (SV) and the HR values during the incremental exercise tests.

Additionally, the application of the HR break point phenomenon is limited because a HR deflection cannot be found even in young subjects in some cases (16). Elsewhere, in 227 healthy young subjects (age: 23 ± 4 yr), Hofmann et al. (14) reported a significant relationship of the HR threshold to the anaerobic lactate threshold (LT) (2) in 85.9% of the subjects who showed a HR deflection. Furthermore, the expression of the linear deviation of HR value, which represented the start of the plateau at maximal HR (HRmax) in the conventional incremental tests, was dependent on the specifics of the Conconi test protocol (17, 27). Although Lucia et al. (22) reported an occurrence of HRDP of 88% in top-level cyclists with thicker heart walls, Jones et al. (16) showed a lack of the HRDP reproducibility in 9 out of 15 well-trained male distance runners who performed a treadmill simulation of the Conconi test protocol. Therefore, HRDP was not demonstrated in a considerable number of highly trained endurance athletes, whereas their HR response was curvilinear during the incremental exercise (22).

Beyond this methodological criticism, the cause of the HRDP phenomena can also be questioned. Although left ventricular ejection fraction (LVEF) increased from rest to the LT in healthy male subjects (12, 25, 26), the break point in the HR-work performance curve became less pronounced or was absent altogether when the decrease in LVEF toward the end of the incremental exercise became more distinct (24). Expressed as higher ejection fraction both at rest and during exercise, it has been established that the endurance-trained athletes had a better systolic function than untrained subjects (10, 13). The regulatory mechanisms, however, appeared similar for athletes and healthy sedentary men (15). However, the ability of athletes to decrease their end-systolic volumes (3) may be due to a better systolic function reflecting an enhanced myocardial contractility, contributing to the maintenance of a large SV during an incremental exercise compared with sedentary subjects (15, 30). The parallel increase in SV and left ventricular end-diastolic volume (EDV) could at least, in part, be contributed to the Frank-Starling mechanism, in either trained or untrained subjects. Considering the increase in the SV value almost until the power associated with the maximal oxygen uptake value (pO2 max) in well-trained subjects, we can hypothesize a cardiovascular origin of the HRDP appearance. Such endurance-trained subjects have also been reported to increase their SV until 90–100% of maximal oxygen uptake (O2 max) in contrast to nontrained subjects (13, 35). Indeed, if this increase in SV could be explained by a greater left ventricular filling in well-trained men (13), only some cases of subjects presented a plateau of SV before the end of exercise, whereas others increased their SV until exhaustion. It would also be interesting to elucidate whether the occurrence of HRDP could be influenced by the SV-power output relationship.

Therefore, the aim of this study was to determine whether the break point [i.e., inflection or deflection according to the different studies (8, 9, 14, 22) in the HR-power curve (HRDP) was concomitant with the achievement of a SV plateau in well-trained subjects who showed a SV increase almost until O2 max.

Conclusion. In the present study, except for the no-HRDP group (n = 6) in which neither a HR point deflection nor a SV plateau was observed before reaching O2 max, most of the variance in the power output at the SVmax value can be predicted by the power output at which HRDP appears. The mechanisms underlying the HRDP could be mediated by cardiodynamic means in well-trained endurance cycling subjects to maintain diastolic filling time to uphold SV value.

[kieran]

[quote="Robh"]
3. Upper linear limit (ULL) is the highest heart rate you should go in a hard race to still have an optimal performance and where the HR has optimal stroke volume.

[Robh]

ULL can reveal a change in what the body is capable of maintaining with some form of appropriate coordination.

I use this point to help differentiate between FTFb and "maximal" efforts in training. It's difficult to use the HR as a guide for this level as it will take too long to get the HR elevated and the person will already start to feel "fatigue".

If you measure the power output during these short steps you can see whether you are able to increase the output over time, and see if your "max" efforts are actually benefitting you. When you go back to the lab, you can see whether there has been any change in your ULL which is very easily influenced by nutrition, rest, fuel stores etc. on any given day but does give you some indication of what is happening to performance at the top end.

[Robh]

[quote="kieran"] hi Rob would that be a sustained effort or a short burst . So I take it it would be a good bit below Max HR, for example my max HR (here I mean the highest HR I have recorded over the last 3 years in racing etc) was just over 200bpm, and I have recorded values close to this several times, but I know from experience (empirical evidence) that to sustain an effort I need to keep my hr about 160 (e.g. on turbo trainer (with big cooling fan) I can keep this up for long periods but if I go to 170 for example I can't.).