Evaluation of Stair Climbing as an Approach for Estimating Heart Rate

Recovery in Daily Activities

Daivaras Sokas

, Andrius Rapalis

1,2

, Andrius Petr

enas

1,2

, Saulius Daukantas

and

Vaidotas Marozas

1,2

Biomedical Engineering Institute, Kaunas University of Technology, Kaunas, Lithuania

Department of Electronics Engineering, Kaunas University of Technology, Kaunas, Lithuania

Keywords:

Stair Climbing, Heart Rate Recovery, Daily Activities, Fitbit, YMCA.

Abstract:

Post-Exercise heart rate recovery (HRR) is a convenient approach to assess cardiovascular autonomic function.

Ordinary stair climbing can be viewed as an alternative HRR test performed in daily activities, and also well-

suited for implementation in wrist-worn devices. This study compares HHR parameters estimated after stair

climbing to those obtained by performing the conventional YMCA bench step test using a custom-made wrist-

worn device and a consumer smart wristband Fitbit Charge 2. The results show that most HHR parameters are

underestimated after stair climbing but still comparable to those obtained from the bench step test. The lowest

relative error, 8–11% on average, was found for the decay of heart rate in 30, 60, and 120 s after the recovery

onset.

1 INTRODUCTION

Post-exercise heart rate recovery (HRR) is a simple

non-invasive approach to assess cardiovascular auto-

nomic function (Jouven et al., 2005; Pec¸anha et al.,

2017). Slower HRR is associated with decreased

physical ﬁtness, cardiovascular diseases, and is a pre-

dictor of death (Jouven et al., 2005; Pec¸anha et al.,

2017). HRR can be improved by cardiac rehabilita-

tion (Streuber et al., 2006; Hai et al., 2010) and even

weight loss (Thomson et al., 2010). Therefore, HRR

trend monitoring could be useful for assessing the ef-

fectiveness of exercise training at home environment.

HRR is assessed using standardised tests that re-

quire specialised equipment and supervision. Hence,

it is inconvenient for use outside the clinical setting.

Improvement in wearable device technology gives op-

portunity to evaluate HRR by using a photoplethys-

mogram (PPG) signal (Sokas et al., 2019). Since stair

climbing is a common daily activity that require phys-

ical effort, and is usually followed by slow walking or

rest, this activity can be considered as an alternative

HRR test performed in free-living conditions.

Our previous work reported the feasibility of esti-

mating HRR parameters after stair climbing using the

wrist-worn device with the embedded PPG and baro-

metric pressure sensors (Sokas et al., 2019). However,

it is unclear how the new approach compares to the

conventional bench step test. Accordingly, the aim of

this study is to compare the agreement of HRR param-

eters estimated after stair climbing to those obtained

by performing the bench step test.

2 MATERIALS AND METHODS

2.1 Study Population and Data

Acquisition

Fifty-four healthy volunteers (18 women), 25.5 ± 8.1

(mean ± SD) years old (range 18 to 50 years), with a

height of 177.4 ± 8.5 cm, weight of 73.7 ± 14.4 kg,

and body mass index of 23.3 ± 3.9 kg/m

were en-

rolled in the study.

The study was performed according to the pro-

tocol given in Figure 1. Participants were asked to

climb four ﬂoors (96 stairs in total) three times at dif-

ferent climbing rate: 48, 72, and 96 steps per minute.

After each activity, the participants had to rest in a

standing position for ﬁve minutes, slowly descend

to the ground ﬂoor and rest for three minutes be-

fore the next activity. The YMCA bench step test

was performed using the protocol described in (Gold-

ing, 2000) during which a participant has to step on

a 30.5 cm high bench for 3 min at a stepping rate

Sokas, D., Rapalis, A., Petr

enas, A., Daukantas, S. and Marozas, V.

Evaluation of Stair Climbing as an Approach for Estimating Heart Rate Recovery in Daily Activities.

DOI: 10.5220/0010184500210025

In Proceedings of the 14th International Joint Conference on Biomedical Engineering Systems and Technologies (BIOSTEC 2021) - Volume 4: BIOSIGNALS, pages 21-25

ISBN: 978-989-758-490-9

5 min

rest

steps/min

5 min

rest

5 min

rest

5 min

rest

3 min

rest

3 min

rest

3 min

rest

15 min

rest

steps/min

3 min

test

Figure 1: The protocol of consecutive stair climbing at different rates and the bench step test. All activities are separated by

rest periods.

of 96 steps per minute (288 steps in total) and to sit

down for 5 min after the exercise is ﬁnished. An elec-

tronic metronome ensured steady stepping rate for

both tests.

Data were acquired using the custom-made wrist-

worn device (Biomedical Engineering Institute, Kau-

nas University of Technology, Kaunas, Lithuania) on

the left wrist and the consumer smart wristband Fit-

bit Charge 2 (Fitbit Inc., San Francisco, CA, USA) on

the right wrist. A wrist-worn device synchronously

acquires electrocardiogram (ECG) at a sampling rate

of 500 Hz, photoplethysmogram (PPG) at a sampling

rate of 100 Hz, and barometric pressure at a sampling

rate of 50 Hz with an altitude resolution of 10 cm.

The consumer smart wristband provides a pulse rate

at intervals of 5 s or longer, depending on the quality

of the PPG signal.

The study was conducted by following the ethi-

cal principles of the Declaration of Helsinki. Identi-

ﬁable information was removed to ensure participant

anonymity.

2.2 Estimation of Heart Rate Recovery

Heart rate normally recovers exponentially thus it can

be approximated by a mono-exponential model. The

exponential model is ﬁtted in a 5 min time interval

after the physical activity and the time-constant τ of

exponential decay is estimated. Detection of the re-

covery onset, i.e., the end of stair climbing, in heart

rate series was performed relying on the procedure

described in (Sokas et al., 2019). The quality of ex-

ponential ﬁtting is assessed via the coefﬁcient of de-

termination which should exceed a ﬁxed threshold of

0.5 to consider the ﬁtting acceptable.

The rapid heart rate decay immediately after the

recovery onset is characterized by the short-term time

constant T30 (Pec¸anha et al., 2017). T30 is found by

ﬁtting a line to the logarithm of heart rate and is the

negative inverse of the slope of the resulting line, ex-

pressed as -1/slope. The decay of heart rate in 30 s,

60 s and 120 s after the recovery onset is denoted

HR30, HR60, and HR120, respectively. The differ-

ence between the maximal heart rate at recovery onset

and the baseline heart rate (i.e., minimal heart rate at

the end of the recovery period) is denoted ∆HR.

3 RESULTS

Figure 2 shows the Bland-Altman plots of HRR pa-

rameters estimated from the reference ECG after stair

climbing at rate of 96 steps/min and the YMCA bench

step test. Given that ordinary stair climbing is less

intense activity than the bench step test, it is unsur-

prising that most parameters are underestimated, with

the exception of HR120 and T30. No bias in estimat-

ing HR120 can be explained by return of heart rate to

baseline, whereas T30 might be less affected by ac-

tivity intensity since it depends on the heart rate slope

rather than on absolute values.

Figure 3 shows that lowest absolute and relative

errors are obtained for HR30, HR60, and HR120,

whereas are larger for the remaining parameters. In-

terestingly, absolute and relative errors estimated us-

ing wrist-worn devices are similar to those obtained

from the reference ECG, suggesting PPG as a useful

signal for HRR estimation.

The impact of stair climbing altitude and different

climbing rate on change in heart rate is illustrated in

Fig. 4. Heart rate tends to increase and then reaches

a plateau at 5 meters of altitude for low climbing in-

tensity (48 steps/min). For climbing rates of 72 and

96 steps/min, heart rate rises rapidly up to 10 me-

tres of altitude and then continues to increase only

marginally.

4 DISCUSSION

With this study we seek to take a further step towards

providing a more comprehensive information about

health status next to available heart rate and physical

activity parameters offered by most consumer wrist-

worn devices.

The stair climbing test has not yet been standard-

ised, probably due to different protocols applied in

BIOSIGNALS 2021 - 14th International Conference on Bio-inspired Systems and Signal Processing

(HR30 + HR30

Y M CA

)/2, bpm

80 100 120 140 160 180

HR30 - HR30

Y M CA

, bpm

-60

-40

-20

1.96 SD

-1.96 SD

Bias

21.5

-43.4

-10.9

HR30

(HR60 + HR60

Y M CA

)/2, bpm

60 80 100 120 140 160

HR60 - HR60

Y M CA

, bpm

-60

-40

-20

1.96 SD

-1.96 SD

Bias

24.3

-36.4

-6.046

HR60

(HR120 + HR120

Y M CA

)/2, bpm

60 80 100 120 140

HR120 - HR120

Y M CA

, bpm

-60

-40

-20

1.96 SD

-1.96 SD

Bias

26.4

-26.4

-0.006

HR120

(∆HR + ∆HR

Y M CA

)/2, bpm

30 40 50 60 70 80

∆HR - ∆HR

Y M CA

, bpm

-50

1.96 SD

-1.96 SD

Bias

3.8

-35.1

-15.7

∆HR

(τ + τ

Y M CA

)/2, s

20 40 60 80 100

τ − τ

Y M CA

, s

-100

-50

1.96 SD

-1.96 SD

Bias

27.6

-76.3

-24.3

(T 30 + T 30

Y M CA

)/2, -1/slope

-1.2 -1 -0.8 -0.6 -0.4

T 30 − T 30

Y M CA

, -1/slope

-1

-0.5

0.5

1.96 SD

-1.96 SD

Bias

0.5

-0.7

-0.1

T 30

Figure 2: Comparison of HRR parameters estimated after stair climbing (rate of 96 steps/min) and by performing the YMCA

bench step test. The parameters are estimated from the reference ECG.

ECGPPGFitbit

Absolute error, bpm

ECGPPGFitbit

Absolute error, bpm

ECGPPGFitbit

Absolute error, bpm

ECGPPGFitbit

Absolute error, bpm

ECGPPGFitbit

100

Absolute error, s

ECGPPGFitbit

0.5

1.5

Absolute error, 1/slope

ECGPPGFitbit

Relative error, %

ECGPPGFitbit

Relative error, %

ECGPPGFitbit

Relative error, %

ECGPPGFitbit

100

Relative error, %

ECGPPGFitbit

100

Relative error, %

ECGPPGFitbit

100

Relative error, %

Figure 3: Absolute (top row) and relative (bottom row) HRR parameter estimation errors when comparing stair climbing at a

rate of 96 steps/min to the YMCA bench step test.

Evaluation of Stair Climbing as an Approach for Estimating Heart Rate Recovery in Daily Activities

Altitude, m

0 2 4 6 8 10 12 14

∆HR, bpm

-10

Altitude, m

0 2 4 6 8 10 12 14

∆HR, bpm

-10

Altitude, m

0 2 4 6 8 10 12 14

∆HR, bpm

-10

Figure 4: ∆HR as a function of altitude for different climbing intensity: a) 48 steps/min, b) 72 steps/min, c) 96 steps/min.

Heart rate is averaged over 1 m of altitude. Altitude data was acquired using the custom-made wrist-worn device.

various studies. Common approach is to instruct pa-

tients (eg, after lung resection (Kubori et al., 2017)) to

climb the maximum number of stairs at a convenient

pace, and to stop only due to exhaustion, leg fatigue

or chest pain. The ability to climb the stairs largely

depends on respiratory system thus the total number

of climbed stairs can be complemented with HRR pa-

rameters to better represent the status of cardiorespi-

ratory system.

Clinical research shows that most established and

reproducible HRR parameters are the decay of heart

rate in 60, 120, and 300 s (Pec¸anha et al., 2017; Fec-

chio et al., 2019). While a single point measurement

is well-suited in a controlled environment (e.g., labo-

ratory), it is less reliable in free-living conditions be-

cause it requires accurate detection of the recovery

onset. Exponential ﬁtting or a short-term time con-

stant should potentially be more stable than the de-

cay measures since a large part of the recovery phase

is involved for estimation. However, our current and

previous (Sokas et al., 2019) ﬁndings show that this

is not the case, probably due to sensitivity of these

parameters to the slope of the HRR curve, which is

affected by insufﬁcient physical load reducing ﬁtting

reliability.

HRR parameters often show increased repro-

ducibility after maximal exercise (Boullosa et al.,

2014), which is more similar to the YMCA bench step

test. Therefore, parameter estimation error can be re-

duced at higher climbing rates, assuming that the de-

cay phase will be better expressed. Our study shows

that 5 to 10 meters of climbing altitude is required to

increase heart rate by 20–30 bpm and reach plateau.

Due to simplicity and similarity to ordinary stair

climbing, we selected the YMCA bench step test as a

reference test in this study. However, the results may

differ if other stair climbing test is employed instead.

5 CONCLUSION

This study shows that most HHR parameters are un-

derestimated after stair climbing however are still

comparable to those obtained from the conventional

bench step test. The decay of heart rate in 30, 60, and

120 s was estimated with the lowest error.

ACKNOWLEDGEMENTS

This work was ﬁnancially supported by the Research

Council of Lithuania (Agreement No. S-MIP-20-54).

REFERENCES

Boullosa, D. A., Barros, E. S., Del Rosso, S., Nakamura,

F. Y., and Leicht, A. S. (2014). Reliability of heart

rate measures during walking before and after run-

ning maximal efforts. International Journal of Sports

Medicine, 35(12):999–1005.

Fecchio, R. Y., Brito, L., Leicht, A. S., Forjaz, C. L.,

and Pec¸anha, T. (2019). Reproducibility of post-

exercise heart rate recovery indices: A systematic re-

view. Autonomic Neuroscience: Basic and Clinical,

221:102582.

Golding, L. A., editor (2000). YMCA Fitness Testing

and Assessment Manual. Human Kinetics Publishers,

Champaign, IL, USA, 4th edition.

Hai, J. J., Siu, C. W., Ho, H. H., Li, S. W., Lee, S., and Tse,

H. F. (2010). Relationship between changes in heart

BIOSIGNALS 2021 - 14th International Conference on Bio-inspired Systems and Signal Processing

rate recovery after cardiac rehabilitation on cardiovas-

cular mortality in patients with myocardial infarction.

Heart Rhythm, 7(7):929–936.

Jouven, X., Empana, J. P., Schwartz, P. J., Desnos, M.,

Courbon, D., and Ducimeti

ere, P. (2005). Heart-rate

proﬁle during exercise as a predictor of sudden death.

New England Journal of Medicine, 352(19):1951–

1958.

Kubori, Y., Matsuki, R., Hotta, A., Morisawa, T., and

Tamaki, A. (2017). Comparison between stair-

climbing test and six-minute walk test after lung

resection using video-assisted thoracoscopic surgery

lobectomy. Journal of physical therapy science,

29(5):902–904.

Pec¸anha, T., Bartels, R., Brito, L. C., Paula-Ribeiro, M.,

Oliveira, R. S., and Goldberger, J. J. (2017). Meth-

ods of assessment of the post-exercise cardiac auto-

nomic recovery: A methodological review. Interna-

tional Journal of Cardiology, 227:795–802.

Sokas, D., Petr

enas, A., Daukantas, S., Rapalis, A., Pali-

akait

e, B., and Marozas, V. (2019). Estimation of heart

rate recovery after stair climbing using a wrist-worn

device. Sensors (Switzerland), 19(9).

Streuber, S. D., Amsterdam, E. A., and Stebbins, C. L.

(2006). Heart rate recovery in heart failure patients

after a 12-week cardiac rehabilitation program. Amer-

ican Journal of Cardiology, 97(5):694–698.

Thomson, R. L., Buckley, J. D., Noakes, M., Clifton, P. M.,

Norman, R. J., and Brinkworth, G. D. (2010). Heart

rate recovery improves after weight loss in overweight

and obese women with polycystic ovary syndrome.

Fertility and Sterility, 93(4):1173–1178.

Evaluation of Stair Climbing as an Approach for Estimating Heart Rate Recovery in Daily Activities