Abstract
This study examines the concurrent validity and reliability of the sit-to-stand test to quantify heart rate response during submaximal exercise in healthy Belgian children.
The importance of physical activity is gaining recognition in children with cardiac or respiratory diseases, and the measurement of heart rate (HR) response during exercise is required.1 The 6-minute walking test (6MWT), which has been verified for validity and reliability in children,2 is the reference field test to measure functional exercise capacity. New field tests are emerging to counteract the practical drawbacks associated with the 6MWT. The 1-minute sit-to-stand test (STST) is easy to implement and has already been validated in adults,3 but not yet in children. Moreover, to our knowledge, the physiological response associated with this test is unknown in children. The aims of this study were to evaluate the concurrent validity and reliability of the STST in measuring the HR response to submaximal exercise and functional exercise capacity in children.
Methods
After ethical approval from the Comité d’Ethique hospitalo-facultaire at Cliniques universitaires St-Luc, registration (NCT03670511), and written informed consent were provided, healthy children aged 8 to 18 years were recruited. The only inclusion criterion was participation in the mandatory medical investigation at school. The exclusion criteria were a diagnosis of chronic lung, cardiac, or neuromuscular disease, motor disability, or being overweight.
Children performed 2 1-minute STSTs4 (STST1 and STST2) with a 1-week interval. Concomitantly to STST1, children performed a 6MWT as a reference test.2 The number of sit-to-stands, walked distance, HR, and HR response (ΔHR initial to final [i-f] and ΔHR final to rest [f-r]) during the test were recorded. The STST concurrent validity (association with the 6MWT), inter-STST agreement (Cohen κ), reliability (intraclass correlation coefficient [ICC]), and repeatability (paired t test after checking for normality [learning effect] and the Bland-Altman method) were verified. Statistical analyses were performed with SPSS, version 25.0 (IMB) and statistical significance was set at P < .05.
Results
Fifty-two children (mean [SD] age, 12.8 [2.4] years) were recruited. All children completed the tests.
Concurrent Validity
The HR and HR responses were similar for both tests (Table 1). However, HR recovery (ΔHRf-r) was faster for the STST than for the 6MWT. The HRf was lower than the theoretical maximal HR for all children and tests (STST1, 70%; 95% CI, 67-73 and 6MWT, 69%; 95% CI, 65-72).
Table 1. Concurrent Validity of the Functional Exercise Capacity and the HR Responses Measured by the STST and the 6MWT in Childrena.
| Measure | Mean (SD) | Difference (95% CI) | P Value | ρ | P Value | ||
|---|---|---|---|---|---|---|---|
| 6MWT | STST1 | Difference Between STST1 and 6MWT | |||||
| Distance, m/STS | 646 (55) | 40 (6) | NA | … | … | 0.178 | .21 |
| HRi, bpm | 92 (15) | 94 (15) | −2 (10) | (−4 to 1) | .18 | 0.785 | <.001 |
| HRf, bpm | 139 (24) | 141 (20) | −2 (17) | (−7 to 3) | .38 | 0.698 | <.001 |
| ΔHRi-f, % | 51 (24) | 51 (22) | −0.3 (23.8) | (−6.9 to 6.3) | .93 | 0.522 | <.001 |
| ΔHRf-r, % | 19 (8) | 22 (9) | −3.5 (8.7) | (−5.8 to −1.1) | .006 | -0.298 | .03 |
Abbreviations: 6MWT, 6-minute walking test; bpm, beats per minute; f, final; HR, heart rate; ΔHRf-r, HR recovery; ΔHRi-f, HR change; i, initial; NA, not applicable; r, rest (2’ posteffort); STS, sit-to-stand; STST, sit-to-stand test.
Data are expressed as mean (SD).
The HR changes (ΔHRi-f) in the STST1 and the 6MWT were moderately and significantly associated with one another (ρ = 0.522; P < .001). The distance was not associated with the number of sit-to-stands (ρ = 0.178; P = .21) (Table 1). No anthropometric parameter was associated with the number of sit-to-stands, unlike age (ρ = 0.294; P = .03).
Reliability and Repeatability
The inter-STST agreement regarding the HR response was weak but statistically significant (κ = 0.24; P = .006). The reliability (ICC) of the HR response (ΔHRi-f and ΔHRf-r) was verified without a learning effect (t test) (Table 2). The bias was −5% (95% CI, −12 to 2) and the limits of agreement were −55% (lower) and 44% (upper).
Table 2. Repeatability and Reliability of the Functional Exercise Capacity and the HR Responses Measured by 2 STSTs in Childrena.
| Measure | Mean (SD) | Repeatability | Reliability | |||||
|---|---|---|---|---|---|---|---|---|
| STST1 | STST2 | Difference Between STST1 and STST2, Mean (SD) | Difference, 95% CI | P Value | ICC, STST1 and STST 2 | Difference, 95% CI | P Value | |
| Distance, m/STS | 40 (6) | 42 (6) | 2 (4) | 1 to 4 | <.001 | 0.90 | 0.832-0.945 | <.001 |
| HRi, bpm | 94 (15) | 92 (15) | −2 (11) | −5.4 to 0.9 | .16 | 0.83 | 0.708-0.903 | <.001 |
| HRf, bpm | 141 (20) | 142 (21) | 1 (17) | −3.9 to 5.7 | .71 | 0.78 | 0.622-0.875 | <.001 |
| ΔHRi-f, % | 51 (22) | 56 (28) | 5.2 (25.2) | 1.8 to 12 | .14 | 0.68 | 0.434-0.814 | <.001 |
| ΔHRf-r, % | 22 (9) | 25 (11) | 2.4 (10.3) | −0.4 to 5.3 | .10 | 0.66 | 0.413-0.807 | <.001 |
Abbreviations: bpm, beats per minute; f, final; HR, heart rate; ΔHRf-r, HR recovery; ΔHRi-f, HR change; i, initial; ICC, intraclass coefficient; r, rest (2’ posteffort); STST, sit-to-stand test.
Data are expressed as mean (SD).
The reliability (ICC) of the number of sit-to-stands was excellent, but a learning effect (t test) was observed (Table 2). The number of repetitions was greater in STST2 than in STST1 in 43 patients (83%). The repeatability of the number of sit-to-stands was verified with a bias of 2.5 (95% CI, 1.5-3.5) and limits of agreement of −4.9% (lower) and 9.9% (upper).
Discussion
To our knowledge, this study demonstrated for the first time the concurrent validity and reliability of the STST to quantify the HR response during submaximal exercise in healthy children. Indeed, the cardiorespiratory responses to the STST and the 6MWT were similar and associated in the sample of healthy children. This result means that the STST is a good alternative field test to the 6MWT to evaluate cardiorespiratory demand. The STST is interesting because its submaximal exercise is similar to the 6MWT, but it is less time-consuming while also requiring fewer resources and no long hallway.
Moreover, the reliability of the cardiorespiratory response measured by the STST at a 1-week interval was verified. Although we cannot consider the STST as a surrogate for the 6MWT for measuring the functional exercise capacity in children because of the lack of association with the walked distance, the STST was reliable for the number of repetitions measurement. The associated learning effect observed for the number of sit-to-stands, which contrasted with the adult results, could be explained by the differences in intrinsic motivation5 and time perception6 between adults and children. The STST could be used complementarily with the maximum incremental cardiopulmonary exercise test or when that test cannot be performed.
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