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Letters to the Editor
number of patients, was performed on cycle-ergometers in a medical center under the supervision of a physician, and required repeated [lactate]b measurements.2,3 These limitations hinder implementation and dissemination of long-term endurance exercise training in the general pop- ulation of SCD patients. The key point was therefore to find a non-invasive marker to adjust exercise intensity during endurance training and physical activity in SCD patients. In this study we proposed and tested HR as the possible surrogate (ClinicalTrials.gov, number NCT02571088).
Data from eight male (53%) and seven female (47%)
adult SCD patients (age: 34±11 years; height: 172±10 cm;
weight: 66±11 kg) were analyzed. Patients successively
underwent a first submaximal incremental test (SIT1), an
8-week endurance exercise training program, and a post-
training SIT (SIT2). SIT1 and SIT2 started at 20 or 30 W
and increased every 2 min by 10 or 15 W for females and
males, respectively. HR and [lactate]b were recorded
every minute. HR was derived from a 12-lead electrocar-
become adequately accustomed to cycling during SIT1, unlike the 13 other patients who adapted rapidly. If the SIT2 data were taken into account for these two patients, the concordance was clear again (Figure 1, panels N and O). As a whole, all HR values recorded during training sessions within the LT1 and 2.5 mmol.L-1 window were associated with [lactate]b close to the target values and never above 4 mmol.L-1 (the safety cutoff).
Another possibility would have been to use patients’ rate of perceived exertion (RPE). However, the sensitivity of RPE appeared (at least in our population) too limited: several patients reported similar RPE for a wide range of power outputs crossing the LT1-2.5 mmol.L-1 window (Figure 2). This large intra- and inter-individual variability may constitute a pitfall to the use of RPE as a means to manage exercise intensity precisely during training ses- sions. However, further studies would be necessary to confirm this point.
Taken together, the present data indicate that HR appears to be an acceptable surrogate to implement endurance exercise, as long as patients’ individual [lactate]b versus HR relationship (obtained during SIT) is known and patients are accustomed to cycling exercise. To ensure safety and obtain benefit, an exercise intensity objectified by HR ranged between LT1 and 2.5 mmol.L-1 obtained during SIT could be used. Further prospective studies would be needed: (i) to confirm the accuracy of HR as a surrogate for [lactate]b during endurance training of SCD patients, and (ii) to determine the frequency with which SIT must be repeated to take into account the improvements/changes induced by endurance training.
Laurent A. Messonnier,1 Manon Riccetti,1 Benjamin Chatel,2 Frédéric Galactéros,3,4 Barnabas Gellen,5 Thomas Rupp,1 Léonard Féasson6,7 and Pablo Bartolucci3,4
1
Université Savoie Mont Blanc, Laboratoire Interuniversitaire de
Biologie de la Motricité, EA7424, Chambéry; 2CellMade, Le Bourget-
du-Lac; 3Sickle Cell Referral Center, UMGGR, Hôpital Henri-
Mondor, Assistance Publique–Hôpitaux de Paris (AP-HP), Université
Paris-Est Créteil (UPEC), Créteil; 4Institut Mondor de Recherche
Biomédicale, Unité 2, INSERM, Hôpital Universitaire Henri-Mondor,
Université Paris-Est Créteil (UPEC), Créteil; 5Department of Cardiac
Rehabilitation, Henri-Mondor University Hospital, Assistance
Publique–Hôpitaux de Paris (AP-HP), Créteil; 6Université de Lyon,
diogram (ErgoCard, Medisoft, Sorinnes, Belgium). For
[lactate]b, a blood drop (10 mL) was taken from the ear-
lobe and tested extemporaneously within 15-20 s
(Lactate Scout+, EKF diagnostics, Cardiff, UK). Exercise
was stopped as soon as [lactate] was ≥4 mmol.L-1. HR b
was determined at the first lactate threshold (LT1) and at 2.5 mmol.L-1 of [lactate]b. Three times a week, patients performed 30-min moderate-intensity cycling exercises, for 8 weeks. [Lactate]b and HR were measured during the training sessions. Data are presented as the mean ± stan- dard deviation. HR and [lactate]b obtained during SIT were correlated using polynomial regressions. Standard errors of the estimate (SEE) to the regression line were calculated.
Figure 1 reports [lactate]b versus HR curves (circles)
obtained during SIT1 for the 15 patients (A to O) and also
during SIT2 for patients N and O. The mean R2 of the
[lactate] versus HR polynomial regressions was b
0.954±0.056. The mean SEE value to the polynomial regression was 0.555±0.388 mmol.L-1. Figure 1 also reports [lactate]b and the associated HR measured during the training sessions (triangles). The mean SEE value of [lactate]b during training to the polynomial regression was 0.714±0.047 mmol.L-1. During training, no patient who had a HR in the range between LT1 and 2.5 mmol.L-1 [lactate] experienced [lactate] ≥4 mmol.L-1.
Université Jean Monnet, Laboratoire Interuniversitaire de Biologie de la bb7
The present study aimed to find a surrogate for [lac-
tate]b to implement and widely disseminate endurance
exercise training among SCD patients. If the conditioning
strategy is to target an exercise intensity low enough to
be safe and elevated enough to induce adaptations, an
exercise intensity between LT1 and 2.5 mmol.L-1
[lactate] might be targeted.4 A safety cutoff should be set b
at 4 mmol.L-1 since above this value blood lactate accu- mulates abruptly and associated acidosis may develop rapidly, especially in SCD.4 We paid particular attention to prevent lactate accumulation-associated acidosis, which constitutes a potentially major exercise-related triggering factor of HbS polymerization, sickling and vaso-occlusive crises.5
A first possibility to implement endurance exercise would be to use the power output corresponding to a tar- get [lactate]b obtained during SIT. However, this would oblige patients to exercise on a cycle ergometer so that any other forms of physical activity would be excluded.
A second possibility would be to use HR. In 13 patients, [lactate]b and the associated HR recorded during training concurred with the correlation obtained during SIT1. We noted that the two remaining patients did not
Motricité, EA 7424, Saint-Etienne and Unité de Myologie, Service de Physiologie Clinique et de l’Exercice, Hôpital Universitaire
de Saint-Etienne, Saint-Etienne, France
Correspondence:
LAURENT A. MESSONNIER - laurent.messonnier@univ-smb.fr doi:10.3324/haematol.2020.267047
Received: July 16, 2020.
Accepted: August 26, 2020.
Pre-published: August 27, 2020.
Disclosures: LAM has received gifts and consulting fees from Addmedica and bluebirdbio, respectively; PB has received grants and/or consulting fees from Addmedica, bluebirdbio, Emmaus, Fondation Fabre, GBT, Hermanext, Novartis and Roche. These gifts, fees
and grants are not relevant to the submitted work.
Contributions: LAM, FG, LF and PB designed and conducted
this study; MR and BC analyzed data; MR created the figures; LAM wrote the first draft of the article. All authors critically reviewed the draft and approved the final version for publication.
Funding: this work was supported in part by research funding from “l’association l’ar’mony”.
haematologica | 2021; 106(5)