Cardiol Res

Cardiology Research, ISSN 1923-2829 print, 1923-2837 online, Open Access

Article copyright, the authors; Journal compilation copyright, Cardiol Res and Elmer Press Inc

Journal website https://www.cardiologyres.org

Original Article

Volume 5, Number 3-4, August 2014, pages 101-107

Evaluation of a New Shirt-Based Electrocardiogram Device for Cardiac Screening in Soccer Players: Comparative Study With Treadmill Ergospirometry

Figure 1. Wireless electrocardiographic monitoring recordings of soccer players during Yo-Yo intermittent recovery test level 1. (A) Activity index during the three phases of the test: warming up, Yo-Yo test and recovery. Physical activity expressed in units of acceleration (g). (B) ECG recording of a patient with multiple artifacts in baseline signal, impeding an accurate analysis of QRS complexes. (C) Interpretable ECG recording.

Figure 2. Relationship between treadmill ergospirometry and Yo-Yo intermittent recovery test level 1 in the calculation of maximum oxygen consumption (VO₂ max).

**Table 1.** Baseline Characteristics of Participants, Yo-Yo Test and Ergospirometry Results, and Heart Rate Variability Parameters Estimated by Nuubo System
BMI: body mass index; bpm: beats per minute; YYIRT: Yo-Yo intermittent recovery test; QTc: corrected QT interval; VO₂: maximal oxygen uptake; g: unit of acceleration; SDNN: standard deviation of normal-to-normal RR intervals; rMSDD: square root of the mean squared differences of successive normal-to-normal RR intervals; pNN50: proportion of interval differences of successive normal-to-normal RR intervals; LF/HF ratio: ratio of low- to high-frequency power. *Calculated only on 16 adequate and interpretable ECG signals.
General characteristics	n = 19
Age (years)	20.1 ± 1.8
BMI (kg/m²)	22.4 ± 1.5
Percentage body fat (%)	11.8 ± 2.0
Blood pressure (mm Hg)	113.3 ± 9.3/67.3 ± 7.2
YYIRT level 1	n = 19
Maximal heart rate (bpm)*	187.7 ± 3.8
Mean QTc (ms)*	398.9 ± 20.2
Distance (m)	2,006.3 ± 282.9
Median stage reached	18.7 (17.6 - 20.7)
Estimated VO₂ (mL/kg/min)	53.3 ± 2.4
Basal lactate (mmol/L)	2.6 ± 0.7
Maximal lactate (mmol/L)	10.4 ± 1.7
Ergospirometry	n = 19
Maximal heart rate (bpm)	190.1 ± 5.5
Time (min)	16.7 ± 0.9
VO₂ (mL/kg/min)	53.7 ± 3.0
Maximal lactate (mmol/L)	8.5 ± 3.3
Aerobic threshold (mL/kg/min)	28.5 ± 6.1
Anaerobic threshold (mL/kg/min)	38.5 ± 4.7
Heart rate variability parameters	n = 16
Mean RR interval (ms)	369.7 ± 27.6
SDNN (ms)	38.7 ± 19.0
rMSDD (ms)	19.1 ± 19.2
pNN50 (%)	2.82 ± 4.4
Mean triangular index	4.45 ± 1.5
LF/HF ratio	1.87 ± 1.0

Table 1. Baseline Characteristics of Participants, Yo-Yo Test and Ergospirometry Results, and Heart Rate Variability Parameters Estimated by Nuubo System

BMI: body mass index; bpm: beats per minute; YYIRT: Yo-Yo intermittent recovery test; QTc: corrected QT interval; VO₂: maximal oxygen uptake; g: unit of acceleration; SDNN: standard deviation of normal-to-normal RR intervals; rMSDD: square root of the mean squared differences of successive normal-to-normal RR intervals; pNN50: proportion of interval differences of successive normal-to-normal RR intervals; LF/HF ratio: ratio of low- to high-frequency power. *Calculated only on 16 adequate and interpretable ECG signals.

General characteristics

n = 19

Age (years)

20.1 ± 1.8

BMI (kg/m²)

22.4 ± 1.5

Percentage body fat (%)

11.8 ± 2.0

Blood pressure (mm Hg)

113.3 ± 9.3/67.3 ± 7.2

YYIRT level 1

n = 19

Maximal heart rate (bpm)*

187.7 ± 3.8

Mean QTc (ms)*

398.9 ± 20.2

Distance (m)

2,006.3 ± 282.9

Median stage reached

18.7 (17.6 - 20.7)

Estimated VO₂ (mL/kg/min)

53.3 ± 2.4

Basal lactate (mmol/L)

2.6 ± 0.7

Maximal lactate (mmol/L)

10.4 ± 1.7

Ergospirometry

n = 19

Maximal heart rate (bpm)

190.1 ± 5.5

Time (min)

16.7 ± 0.9

VO₂ (mL/kg/min)

53.7 ± 3.0

Maximal lactate (mmol/L)

8.5 ± 3.3

Aerobic threshold (mL/kg/min)

28.5 ± 6.1

Anaerobic threshold (mL/kg/min)

38.5 ± 4.7

Heart rate variability parameters

n = 16

Mean RR interval (ms)

369.7 ± 27.6

SDNN (ms)

38.7 ± 19.0

rMSDD (ms)

19.1 ± 19.2

pNN50 (%)

2.82 ± 4.4

Mean triangular index

4.45 ± 1.5

LF/HF ratio

1.87 ± 1.0

**Table 2.** Comparative Results Between Yo-Yo Test With Nuubo’s Technology and Ergospirometry
	ICC (95% CI)	P value
ICC: intra-class correlation coefficient; CI: confidence interval; VO₂: maximal oxygen uptake; PC: premature complex.
Quantitative variables
Baseline heart rate	0.95 (0.87 - 0.97)	< 0.001
Peak heart rate	0.61 (0.21 - 0.83)	0.003
VO₂ max	0.84 (0.63 - 0.93)	< 0.001
ICC: intra-class correlation coefficient; CI: confidence interval; VO₂: maximal oxygen uptake; PC: premature complex.
Qualitative variables
Adequate baseline ECG	1	< 0.001
Adequate peak ECG	0.45	0.018
Atrial PC	1	< 0.001
Ventricular PC	1	< 0.001
ST segment depression	1	< 0.001

Table 2. Comparative Results Between Yo-Yo Test With Nuubo’s Technology and Ergospirometry

ICC (95% CI)

P value

ICC: intra-class correlation coefficient; CI: confidence interval; VO₂: maximal oxygen uptake; PC: premature complex.

Quantitative variables

Baseline heart rate

0.95 (0.87 - 0.97)

< 0.001

Peak heart rate

0.61 (0.21 - 0.83)

0.003

VO₂ max

0.84 (0.63 - 0.93)

< 0.001

Kappa index

P value

ICC: intra-class correlation coefficient; CI: confidence interval; VO₂: maximal oxygen uptake; PC: premature complex.

Qualitative variables

Adequate baseline ECG

< 0.001

Adequate peak ECG

0.45

0.018

Atrial PC

< 0.001

Ventricular PC

< 0.001

ST segment depression

< 0.001