Validity of the Polar H10 Sensor for Heart Rate Variability Analysis during Resting State and Incremental Exercise in Recreational Men and Women

Acute effect of aerobic exercise on inhibitory control and task-related heart rate variability in preadolescent children

OBJECTIVES

To investigate whether a single session of aerobic exercise improves inhibitory control in preadolescent children and whether this effect is mediated by changes in parasympathetic activity.

DESIGN

In this experimental study, an intervention and control group were pair-matched by age, sex and moderate-to-vigorous physical activity.

METHOD

114 participants either completed a 20 min moderately-intense exercise bout on a cycling ergometer or watched a 20 min video. Prior to and after these conditions, a computer-based Stroop task was administered. During the cognitive task, heart rate variability (HRV) was measured using electrocardiography.

RESULTS

Path-analyses did not support an association between group and posttest accuracy on the Stroop task, while controlling for pretest scores. However, the intervention group had lower time-domain based HRV at posttest. The examination of mediation models revealed a moderation by sex, as the relation of lower time-domain based HRV with higher accuracy on both congruent and incongruent trials of the Stroop task was observed in girls only.

CONCLUSION

A single aerobic exercise session does not necessarily improve inhibitory control in preadolescent children. However, the manipulation of the autonomic state towards a parasympathetic withdrawal has the potential to alter inhibitory control in girls in particular.

The Effects of Caffeine on Heart Rate and Heart Rate Variability at Rest and During Submaximal Cycling Exercise

The aim of this study was to investigate the effects of caffeine on heart rate and heart rate variability (HRV) at rest and during submaximal exercise. Using a balanced, double-blind, randomized, crossover design, 16 male cyclists (age: 37 ± 9 years; V ˙ O2max: 4.44 ± 0.67 L·min-1) completed three trials in an air-conditioned laboratory. In Trial 1, cyclists completed two incremental cycling tests to establish the V ˙ O2-power output relationship and V ˙ O2max. In trials 2 and 3, cyclists were evaluated for heart rate and HRV at rest, after which they ingested a capsule containing 5 mg·kg-1 of caffeine or placebo. Thirty-five minutes post-supplementation, additional resting heart rate and HRV readings were taken after which cyclists completed a submaximal incremental cycling test (6 min stages) at 40-80% of V ˙ O2max; with HR and HRV measurements taken in the last 5 min of each increment. HRV was determined from the root mean square of successive differences between R-R intervals. There were significant supplement × exercise intensity interactions on heart rate (p = .019) and HRV (p = .023), with post hoc tests on the latter showing that caffeine increased HRV at 40%, 50%, and 60% of V ˙ O2max by 3.6 ± 4.9, 2.6 ± 2.8, and 0.6 ± 1.7 ms, respectively. There was a supplement × time interaction effect on resting HRV (p < .001), but not on heart rate (p = .351). The results of this study support the suggestion that caffeine increases the parasympathetic modulation of heart rate.Clinical trial registration number: NCT05521386.

Recent advances in the tools and techniques for AI-aided diagnosis of atrial fibrillation

Atrial fibrillation (AF) is recognized as a developing global epidemic responsible for a significant burden of morbidity and mortality. To counter this public health crisis, the advancement of artificial intelligence (AI)-aided tools and methodologies for the effective detection and monitoring of AF is becoming increasingly apparent. A unified strategy from the international research community is essential to develop effective intelligent tools and technologies to support the health professionals for effective surveillance and defense against AF. This review delves into the practical implications of AI-aided tools and techniques for AF detection across different clinical settings including screening, diagnosis, and ambulatory monitoring by reviewing the revolutionary research works. The key finding is that the advance in AI and its use for automatic detection of AF has achieved remarkable success, but collaboration between AI and human intelligence is required for trustworthy diagnostic of this life-threatening cardiac condition. Moreover, designing efficient and robust intelligent algorithms for onboard AF detection using portable and implementable computing devices with limited computation power and energy supply is a crucial research problem. As modern wearable devices are equipped with sophisticated embedded sensors, such as optical sensors and accelerometers, hence photoplethysmography and ballistocardiography signals could be explored as an affordable alternative to electrocardiography (ECG) signals for AF detection, particularly for the development of low-cost and miniature screening and monitoring devices.

Effects of Missing Data on Heart Rate Variability Measured From A Smartwatch: Exploratory Observational Study

BACKGROUND

Measuring heart rate variability (HRV) through wearable photoplethysmography sensors from smartwatches is gaining popularity for monitoring many health conditions. However, missing data caused by insufficient wear compliance or signal quality can degrade the performance of health metrics or algorithm calculations. Research is needed on how to best account for missing data and to assess the accuracy of metrics derived from photoplethysmography sensors.

OBJECTIVE

This study aimed to evaluate the influence of missing data on HRV metrics collected from smartwatches both at rest and during activity in real-world settings and to evaluate HRV agreement and consistency between wearable photoplethysmography and gold-standard wearable electrocardiogram (ECG) sensors in real-world settings.

METHODS

Healthy participants were outfitted with a smartwatch with a photoplethysmography sensor that collected high-resolution interbeat interval (IBI) data to wear continuously (day and night) for up to 6 months. New datasets were created with various amounts of missing data and then compared with the original (reference) datasets. 5-minute windows of each HRV metric (median IBI, SD of IBI values [STDRR], root-mean-square of the difference in successive IBI values [RMSDRR], low-frequency [LF] power, high-frequency [HF] power, and the ratio of LF to HF power [LF/HF]) were compared between the reference and the missing datasets (10%, 20%, 35%, and 60% missing data). HRV metrics calculated from the photoplethysmography sensor were compared with HRV metrics calculated from a chest-worn ECG sensor.

RESULTS

At rest, median IBI remained stable until at least 60% of data degradation (P=.24), STDRR remained stable until at least 35% of data degradation (P=.02), and RMSDRR remained stable until at least 35% data degradation (P=.001). During the activity, STDRR remained stable until 20% data degradation (P=.02) while median IBI (P=.01) and RMSDRR P<.001) were unstable at 10% data degradation. LF (rest: P<.001; activity: P<.001), HF (rest: P<.001, activity: P<.001), and LF/HF (rest: P<.001, activity: P<.001) were unstable at 10% data degradation during rest and activity. Median IBI values calculated from photoplethysmography sensors had a moderate agreement (intraclass correlation coefficient [ICC]=0.585) and consistency (ICC=0.589) and LF had moderate consistency (ICC=0.545) with ECG sensors. Other HRV metrics demonstrated poor agreement (ICC=0.071-0.472).

CONCLUSIONS

This study describes a methodology for the extraction of HRV metrics from photoplethysmography sensor data that resulted in stable and valid metrics while using the least amount of available data. While smartwatches containing photoplethysmography sensors are valuable for remote monitoring of patients, future work is needed to identify best practices for using these sensors to evaluate HRV in medical settings.

Functional Capacity Impairment in Long COVID After 17 Months of Severe Acute Disease

Long COVID represents a significant challenge in understanding the prolonged impact of the disease. Despite its increasing recognition, detailed insights into the long-term cardiopulmonary consequences remain sparse. This study aimed to evaluate the functional capacity of individuals with persistent symptoms after severe COVID-19 infection compared to control individuals without symptomatic COVID or mild COVID after 17 months. This is a case-control study assessing 34 individuals divided into two groups regarding functional capacity by distance in a 6-min walk test (D6MWT) associated with gas analysis, spirometry, respiratory muscle strength, and quality of life. During the 6 MWT, an important lower heart rate (HR) was observed for the COVID group (106 ± 10 bpm, difference mean: 21.3; p < 0.001), with greater exertional perception (Borg dyspnea: 4.5 [2.0-9.0], p < 0.001 and Borg fatigue: 4.0 [2.0-7.0], p = 0.01), a significant decrease in the distance covered (416 ± 94 m, difference mean: 107; p = 0.002), and a low value of O2 uptake (V˙O2) (11 ± 5.0 mL/(kg min), difference mean: 8.3; p = 0.005) and minute ventilation (22 ± 8 L/min, difference mean: 18.6; p = 0.002), in addition to very low quality of life scores. Regression analysis showed a significant association between D6MWT and Borg fatigue and Borg dyspnea at rest (p = 0.003; p = 0.009). V˙O2 and HR were also significantly associated with the outcomes of the D6MWT (p = 0.04 and p = 0.004, respectively). In conclusion, individuals who have severe COVID-19 and persist with symptoms have low functional capacity, low V˙O2, low HR behavior, and low quality of life.

Validity of heart rate measurements in wrist-based monitors across skin tones during exercise

PURPOSE

To evaluate the accuracy of a wrist-based heart rate (HR) monitor at different exercise intensities across different skin tones.

METHODS

Using a cross-sectional design, we compared HR measures from the wrist-based photoplethysmography Fitbit Charge 5 to the Polar H10 chest strap at rest and during the YMCA Protocol using a recumbent cycle ergometer. Participant were grouped into three skin tone categories: light (Fitzpatrick Scale Skin Types 1+2), medium (Types 3+4), and darker skin tone (Types 5+6). HR measures using the Polar chest strap during the exercise test were categorized as <40%, 40-60%, or >60% HR reserve (HRR). Absolute error in beats per minute (bpm) between the two devices was calculated for each measure. A linear mixed effects model was used to assess interaction effects between skin tone and exercise intensity, with participants as the random effect. Bland-Altman plots were used for visual analyses.

RESULTS

Twenty-five participants [mean (SD): 25.8 (1.9) years old; 64% female] were included with 495 observations of simultaneous Fitbit and Polar HR recordings collected during exercise. During exercise, we observed a statistically significant interaction effect between skin tone and exercise intensity. Compared with light skin tone at <40% HRR, mean error was greater for medium skin tone at >60% HRR [mean error (95%CI): 11.8 (5.6-17.9) bpm, p<0.001] and darker skin tone at 40-60% HRR [7.6 (1.7-13.5) bpm, p = 0.011] and >60% HRR [11.7 (5.3-18.0) bpm, p<0.001].

CONCLUSION

HR measurement error using a wrist-based device was greater with increasing exercise intensity for people with darker skin tones.

Fractal correlation properties of heart rate variability and respiratory frequency as measures of endurance exercise durability

PURPOSE

Field-based measures of durability (exercise-related physiologic deterioration over time) for assessing athletic fitness often rely on changes in maximal power profiles or heart rate (HR) drift. This study aimed to determine whether an index of HR variability based on the short-term exponent of Detrended Fluctuation Analysis (DFA a1) along with respiratory frequency (fB) could demonstrate changes in durability during a Time to Task Failure (TTF) Trial.

METHODS

Ten participants performed a cycling TTF at an intensity of 95% of the respiratory compensation point (RCP) on two occasions, Control and a "Reward" where a monetary incentive was offered when task failure was signaled. Metabolic responses including oxygen uptake (V ˙ O 2 ), lactate and glucose along with HR, DFA a1 and fB were measured and compared over each quarter of the TTF up to the time of signaling (Q1, Q2, Q3, and Q4).

RESULTS

The elapsed time of TTF sessions was statistically similar (p = 0.54). After initial equilibration, metabolic responses remained largely stable over Q2-Q4. HR, DFA a1 and fB displayed drift over Q2-Q4 with significant ANOVA. Repeatability of quarterly HR, DFA a1, and fB between Control and Reward sessions was high with ICC between 0.73 and 0.94, Pearson's r was between 0.83 and 0.98 with no difference in mean values by paired t testing.

CONCLUSION

HR, fB and DFA a1 are useful metrics representing alteration in physiologic characteristics demonstrating durability loss during an endurance exercise session. These measures were repeatable across sessions and have the potential to be monitored retrospectively or in real time in the field with low-cost consumer equipment.

Detrended fluctuation analysis to determine physiologic thresholds, investigation and evidence from incremental cycling test

PURPOSE

Training zones are generally assessed by gas-exchange thresholds (GET). Several mathematical analyses of heart rate variability (HRV) are proposed for indirect GET determination. Our study aimed to investigate the accordance of the detrend fluctuation analysis (DFA α1) for determining GET with first (VT1) and second ventilatory (VT2) thresholds in well-trained subjects.

METHODS

Eighteen female and 38 male sub-elite cyclists performed a maximal incremental cycling test of 2-min stage duration with continuous gas exchange and HR measurements. Power output (PO), Oxygen uptake ( V ˙ O2) and HR at VT1 and VT2 were compared with DFA α1 0.75 (HRVT1) and 0.50 (HRVT2). Agreements between PO, V ˙ O2 and HR values were analyzed using Bland-Altman analysis.

RESULTS

Large limits of agreement between VT1 and HRVT1 were observed for measures of V ˙ O2 expressed in mL.min-1.kg-1 [- 21.3; + 14.1], HR [ 39.2; + 26.9] bpm and PO [- 118; + 83] watts. Indeed, agreements were also low between VT2 and HRVT2 for measures of V ˙ O2 [- 26.7; + 4.3] mL.min-1.kg-1, HR [- 45.5; + 10.6] bpm and PO [- 157; + 35] watts. Our results also showed a sex effect: women obtained worst predictions based on DFA α1 than men for HR (p = 0.014), PO (p = 0.044) at VT1 andV ˙ O 2 (p = 0.045), HR (p = 0.003) and PO (p = 0.004) at VT2.

CONCLUSION

There was unsatisfactory agreement between the GET and DFA α1 methods for VT1 and VT2 determination in both sex well-trained cyclists. Trial registration number 2233534 on 2024/03/05 retrospectively registered.

Examining the Feasibility and Acceptability of Identifying Signs of Social Anxiety, in University Students Aged 18-25, While Watching 360° Immersive Films

Timely, accurate assessment and treatment for social anxiety disorder (SAD) in young people is crucial. There is potential for the adoption of tailored virtual reality interventions for a complementary diagnostic tool using heart rate monitoring as a response indicator. This study examined the feasibility and acceptability of this concept by exposing healthy individuals, aged 18-25, to developed 360° immersive films while collecting heart rate sensor data. Two immersive scenarios were designed with a participatory advisory youth group. A clinical consultant nurse mapped scenario events against validated routine assessment subscales in child and adolescent services. The films were shown to seven participants through a VR headset while monitoring heart rate. They provided qualitative feedback on their quality, acceptability and usability. The study indicated that this approach has the potential to enhance assessments in child and adolescent mental health services. The study has several limitations which are discussed with recommendations for consideration if this concept is taken further. The intervention could act as a potential portable, user-friendly complementary diagnostic tool for clinicians in practice. However, further research is needed to examine its validity.

Reliability and Accuracy of the Fitbit Charge 4 Photoplethysmography Heart Rate Sensor in Ecological Conditions: Validation Study

Background

Wrist-worn photoplethysmography (PPG) sensors allow for continuous heart rate (HR) measurement without the inconveniences of wearing a chest belt. Although green light PPG technology reduces HR measurement motion artifacts, only a limited number of studies have investigated the reliability and accuracy of wearables in non-laboratory-controlled conditions with actual specific and various physical activity movements.

Objective

The purpose of this study was to (1) assess the reliability and accuracy of the PPG-based HR sensor of the Fitbit Charge 4 (FC4) in ecological conditions and (2) quantify the potential variability caused by the nature of activities.

Methods

We collected HR data from participants who performed badminton, tennis, orienteering running, running, cycling, and soccer while simultaneously wearing the FC4 and the Polar H10 chest belt (criterion sensor). Skin tone was assessed with the Fitzpatrick Skin Scale. Once data from the FC4 and criterion data were synchronized, accuracy and reliability analyses were performed, using intraclass correlation coefficients (ICCs), Lin concordance correlation coefficients (CCCs), mean absolute percentage errors (MAPEs), and Bland-Altman tests. A linear univariate model was also used to evaluate the effect of skin tone on bias. All analyses were stratified by activity and pooled activity types (racket sports and running sports).

Results

A total of 77.5 hours of HR recordings from 26 participants (age: mean 21.1, SD 5.8 years) were analyzed. The highest reliability was found for running sports, with ICCs and CCCs of 0.90 and 0.99 for running and 0.80 and 0.93 for orienteering running, respectively, whereas the ICCs and CCCs were 0.37 and 0.78, 0.42 and 0.88, 0.65 and 0.97, and 0.49 and 0.81 for badminton, tennis, cycling, and soccer, respectively. We found the highest accuracy for running (bias: 0.1 beats per minute [bpm]; MAPE 1.2%, SD 4.6%) and the lowest for badminton (bias: -16.5 bpm; MAPE 16.2%, SD 14.4%) and soccer (bias: -16.5 bpm; MAPE 17.5%, SD 20.8%). Limit of agreement (LOA) width and artifact rate followed the same trend. No effect of skin tone was observed on bias.

Conclusions

LOA width, bias, and MAPE results found for racket sports and soccer suggest a high sensitivity to motion artifacts for activities that involve "sharp" and random arm movements. In this study, we did not measure arm motion, which limits our results. However, whereas individuals might benefit from using the FC4 for casual training in aerobic sports, we cannot recommend the use of the FC4 for specific purposes requiring high reliability and accuracy, such as research purposes.

Modelling heart rate dynamics in relation to speed and power output in sprint kayaking as a basis for training evaluation and optimisation

With the development of power output sensors in the field of paddle sports and the ongoing advancements in dynamical analysis of exercise data, this study aims to model the measurements of external training intensity in relation to heart rate (HR) time-series during flat-water kayak sprint. Nine elite athletes performed a total of 47 interval training sessions with incremental intensity (light to (sub-) maximal effort levels). The data of HR, speed and power output were measured continuously and rating of perceived exertion and blood lactate concentration ([BLa]) were sampled at the end of each interval stage. Different autoregressive-exogenous (ARX) modelling configurations are tested, and we report on which combination of input (speed or power), model order (1st or 2nd), parameter estimation method (time-(in)variant) and training conditions (ergometer or on-water) is best suited for linking external to internal measures. Average model R2 values varied between 0.60 and 0.97, with corresponding average root mean square error values of 15.6 and 3.2 bpm. 1st order models with time-varying (TV) parameter estimates yield the best model performance (average R2 = 0.94). At the level of the individual athlete, the TV modelling features (i.e., the model parameters and derivatives such as time constant values) show significant repeated measure correlations in relation to measures of exercise intensity. In conclusion, the study provides a comprehensive description of how the dynamic relationship between external load and HR for sprint kayaking training data can be modelled. Such models can be used as a basis for improving training evaluation and optimisation.

The Impact of Autonomic Nervous System Modulation on Heart Rate Variability and Musculoskeletal Manifestations in Chronic Neck Pain: A Double-Blind Randomized Clinical Trial

Background: The role of autonomic nervous system (ANS) modulation in chronic neck pain remains elusive. Transcutaneous vagus nerve stimulation (t-VNS) provides a novel, non-invasive means of potentially mitigating chronic neck pain. This study aimed to assess the effects of ANS modulation on heart rate variability (HRV), pain perception, and neck disability. Methods: In this double-blind randomized clinical trial, 102 participants with chronic neck pain were randomly allocated to one of three groups: t-VNS plus standard-care physiotherapy (SC-PT), heart rate variability biofeedback (HRV-BF) with SC-PT, or SC-PT alone. Interventions were administered three times weekly for 6 weeks. The following outcome measures were assessed at baseline and after 6 weeks: HRV, the visual analog scale (VAS), the pressure pain threshold (PPT), and the neck disability index (NDI). Results: The t-VNS group exhibited significant improvements compared to the HRV-BF and SC-PT groups. Specifically, t-VNS increased the RR interval (mean difference [MD] = 35.0 ms; p = 0.037) and decreased the average heart rate (MD = -5.4 bpm; p = 0.039). Additionally, t-VNS reduced the VAS scores (versus HRV-BF: MD = -0.8 cm, p = 0.044; SC-PT: MD = -0.9 cm, p = 0.018), increased the PPT (versus HRV-BF: MD = 94.4 kPa, p < 0.001; SC-PT (MD = 56.2 kPa, p = 0.001)), and lowered the NDI scores (versus HRV-BF: MD = -4.0, p = 0.015; SC-PT: MD = -5.9, p < 0.001). Conclusions: t-VNS demonstrated superior effectiveness compared to HRV-BF and SC-PT in regulating HRV, alleviating pain, and enhancing functional capabilities in individuals with chronic neck pain.

Impact of COVID-19 on heart rate variability in post-COVID individuals compared to a control group

This study investigated the impact of mild COVID-19 on HRV in groups stratified by time after infection and to compare to a healthy group of the same age without previous virus infection and without need of hospitalization. This is a cross-sectional study. We divided the sample into four groups: control group (CG) (n = 31), group 1 (G1): ≤6 weeks (n = 34), group 2 (G2): 2-6 months (n = 30), group 3 (G3): 7-12 months (n = 35) after infection. For HRV analysis, we used the indices of linear (time and frequency domain) and non-linear analysis. For comparisons between groups, ANOVA one way test or Kruskal-Wallis was used according to the data distribution. The effect size was calculated based on Cohen's d or η2. Simple and multiple linear regressions were performed to investigate the interaction between clinical outcomes and HRV parameters. A total of 130 individuals were included. Groups G1 and G2 showed less parasympathetic modulation when compared to CG (p < 0.05), while G3 showed an increase in parasympathetic modulation when compared to G1 (p < 0.05). Moderate to large effect sizes were found according to Cohen d or η2. The multiple linear regression models identified age and infection duration as significant predictors for RMSSD (adjusted R2 = 0.227) and SD1 (adjusted R2 = 0.242), while age was significant for SDNN (adjusted R2 = 0.213). BMI, hypertension, and dyslipidemia were non-significant in all models. For HF (n.u.), infection duration was consistently significant, with stress emerging as a predictor in Model 2 (adjusted R2 = 0.143). The recovery time since diagnosis and age influences recovery from HRV, suggesting a transient effect of the disease on the autonomic nervous system.

Changes in heart rate variability at rest and during exercise in patients after a stroke: a feasibility study

The aim of this study was to evaluate the feasibility of using a biofeedback-enhanced robotics-assisted tilt table (RATT) to investigate time- and intensity-dependent changes in heart rate variability (HRV) at rest and during heart rate-controlled exercise in patients recovering from a stroke. Twelve patients (age 55.3 years ± 15.6 years, 7 women) completed two separate measurement sessions. The first involved familiarization and system identification to determine parameters of a feedback system for automatic control of heart rate (HR). The second comprised 14 min of rest and 21 min of active exercise during which HR was held constant using feedback control to eliminate cardiovascular drift. HR data were collected using a chest-belt HR sensor, and raw RR intervals were employed for HRV analysis during periods of rest (0-7 min and 7-14 min) and exercise (5-13 min and 13-21 min). A biofeedback-enhanced, robotics-assisted tilt table can be successfully employed to perform heart rate-controlled exercises in patients after a stroke. All HRV metrics were substantially lower during exercise compared to rest. In the rest period, HRV values during 0-7 min were lower than during 7-14 min, in line with a slight HR decrease over the entire rest period. During exercise, HRV values during 5-13 min were higher than during 13-21 min, suggesting a time-dependent HRV decrease. All HRV metrics exhibited intensity- and time-dependent changes: higher HRV at rest and decreasing HRV over time. Understanding these HRV characteristics will support the development of heart rate-controlled exercise regimens and protocols for examining HRV changes during exercise in patients.

Validation of a Wearable Sensor Prototype for Measuring Heart Rate to Prescribe Physical Activity: Cross-Sectional Exploratory Study

BACKGROUND

Wearable sensors are rapidly evolving, particularly in health care, due to their ability to facilitate continuous or on-demand physiological monitoring.

OBJECTIVE

This study aimed to design and validate a wearable sensor prototype incorporating photoplethysmography (PPG) and long-range wide area network technology for heart rate (HR) measurement during a functional test.

METHODS

We conducted a transversal exploratory study involving 20 healthy participants aged between 20 and 30 years without contraindications for physical exercise. Initially, our laboratory developed a pulse wearable sensor prototype for HR monitoring. Following this, the participants were instructed to perform the Incremental Shuttle Walk Test while wearing the Polar H10 HR chest strap sensor (the reference for HR measurement) and the wearable sensor. This test allowed for real-time comparison of HR responses between the 2 devices. Agreement between these measurements was determined using the intraclass correlation coefficient (ICC3.1) and Lin concordance correlation coefficient. The mean absolute percentage error was calculated to evaluate reliability or validity. Cohen d was used to calculate the agreement's effect size.

RESULTS

The mean differences between the Polar H10 and the wearable sensor during the test were -2.6 (95% CI -3.5 to -1.8) for rest HR, -4.1 (95% CI -5.3 to -3) for maximum HR, -2.4 (95% CI -3.5 to -1.4) for mean test HR, and -2.5 (95% CI -3.6 to -1.5) for mean recovery HR. The mean absolute percentage errors were -3% for rest HR, -2.2% for maximum HR, -1.8% for mean test HR, and -1.6% for recovery HR. Excellent agreement was observed between the Polar H10 and the wearable sensor for rest HR (ICC3.1=0.96), mean test HR (ICC3.1=0.92), and mean recovery HR (ICC3.1=0.96). The agreement for maximum HR (ICC3.1=0.78) was considered good. By the Lin concordance correlation coefficient, the agreement was found to be substantial for rest HR (rc=0.96) and recovery HR (rc=0.96), moderate for mean test HR (rc=0.92), and poor for maximum HR (rc=0.78). The power of agreement between the Polar H10 and the wearable sensor prototype was large for baseline HR (Cohen d=0.97), maximum HR (Cohen d=1.18), and mean recovery HR (Cohen d=0.8) and medium for mean test HR (Cohen d= 0.76).

CONCLUSIONS

The pulse-wearable sensor prototype tested in this study proves to be a valid tool for monitoring HR at rest, during functional tests, and during recovery compared with the Polar H10 reference device used in the laboratory setting.

Comparison of 1-hour floatation-REST versus conventional napping on heart rate variability in active individuals

Objectives

This study aimed to investigate the short-term effects of a 1-hour floatation-resting environmental therapy (FLO) versus conventional napping (NAP) on heart rate variability (HRV) in highly trained individuals.

Methods

20 non-fatigued participants underwent a prospective randomised interventional study comparing the impacts of FLO and NAP on both supine and standing HRV. Measurements were taken before and after each intervention under controlled conditions, and subjective experiences were assessed through questionnaires.

Results

FLO and NAP were associated with changes in HRV parameters but did so differently. NAP significantly enhanced supine parasympathetic activity, as evidenced by increased log-transformed root mean square of successive differences (p=0.02) and power spectral density (p=0.03) relative to heart rate (HR) values, confirming its effectiveness in promoting autonomic recovery. In contrast, despite being better perceived regarding subjective well-being (p=0.04), FLO conferred no significant changes in supine root mean square of successive differences and decreased power spectral density relative to HR (p=0.02). However, post-intervention comparisons were not statistically different. While supine HR decreased significantly following both interventions, standing HR measurements showed a non-significant increase for FLO compared with NAP (p=0.056).

Conclusion

In highly trained individuals, FLO and NAP demonstrated minimal impact on acute autonomic function. NAP appears more effective for enhancing short-term parasympathetic activity, while FLO provides a more enjoyable experience. These findings underscore the importance of personalised recovery strategies and emphasise the need for further research into individual responses and the long-term effects of these interventions.

12-week melatonin intake attenuates cardiac autonomic dysfunction and oxidative stress in multiple sclerosis patients: a randomized controlled trial

Multiple sclerosis (MS) can induce cardiac autonomic dysfunction identified by a decreased heart rate variability (HRV) which was linked to oxidative stress, vitamin D deficiency and sleep disturbance. Previous MS studies revealed the antioxidant and anti-inflammatory effects of exogenous melatonin, as well as its benefits on sleep and vitamin D. We aimed to investigate the change in HRV, oxidative stress, systemic inflammation and sleep following melatonin supplementation in MS patients. Participants were randomly allocated to either a melatonin group (MG, n = 15) or a placebo group (PG, n = 12) (3 mg/night during 12 weeks). Pre- and post-tests included HRV analysis (Kubios software), sleep dairy and biological analysis [oxidative stress biomarkers (malondialdehyde (MDA), advanced oxidation protein products (AOPP) and reduced glutathione (GSH)); 25-hydroxyvitamin D; C-reactive protein and cholinesterase Gen.2 (CHE2)]. Based on the pre-post supplementation change (Δ (T1₋T0)), melatonin increased the root mean square of successive differences between normal heartbeats [ΔMG (14.17 ± 16.93) vs. ΔPG (₋8.61 ± 12.67), p = 0.0007] and the HRV high-frequency band [ΔMG (6.86 ± 14.85) vs. ΔPG (₋12.58 ± 13.30), p = 0.0016] comparatively with placebo. MG showed a decrease in the HRV low-frequency band [ΔMG (₋4.96 ± 10.08) vs. ΔPG (10.22 ± 13.54), p = 0.003] as well as in the MDA [ΔMG (₋2.27 ± 1.92) vs. ΔPG (0.22 ± 2.30), p = 0.005] and AOPP levels [ΔMG (₋113.97 ± 137.72) vs. ΔPG (156.46 ± 230.52), p = 0.0008] compared with PG. Melatonin enhanced the GSH [ΔMG (10.51 ± 14.93) vs. ΔPG (₋5.05 ± 10.18), p = 0.004] and CHE2 levels [ΔMG (407.07 ± 723.26) vs. ΔPG (₋22.92 ± 506.52), p = 0.029] as well as sleep quality [scores: ΔMG (1.50 ± 1.28) vs. ΔPG (₋1.05 ± 2.05), p = 0.0006] and quantity [weighted total sleep time: ΔMG (0.74 ± 1.14) vs. ΔPG (₋1.04 ± 1.00), p = 0.0003] comparatively with placebo. Caregivers may recommend 12-week nocturnal melatonin intake to attenuate cardiac autonomic dysfunction, oxidative stress and sleep disorders in MS patients.Clinical registration This study was prospectively registered in the Pan African Clinical Trial Registry database (PACTR202007465309582) on 23 July 2020 ( https://pactr.samrc.ac.za/ .).

The Effect of Immersive Virtual Reality on Dental Anxiety and Intraoperative Pain in Adults Undergoing Local Anesthesia: A Randomized Clinical Trial

AIMS

This study assessed the effect of immersive virtual reality (IVR) on anxiety and intraoperative pain in adult patients undergoing dental extractions with local anesthesia.

METHODS

In a single-blind, randomized clinical trial from September 2022 to December 2023 at a private dental clinic, 190 patients with dental anxiety were randomly assigned to either an IVR or a control group. Primary outcomes-dental anxiety and perioperative pain-were measured using the State-Trait Anxiety Inventory (STAI), Modified Dental Anxiety Scale (MDAS), and Visual Analogue Scale (VAS) before and after the procedure. Secondary outcomes included heart rate (HR), diastolic blood pressure (DBP), and systolic blood pressure (SBP), recorded at various stages.

RESULTS

The IVR group showed significant reductions in total anxiety, state anxiety, and MDAS scores compared to the control group (p < 0.001). Pain intensity was also lower in the IVR group (p = 0.03). Additionally, heart rate (HR), systolic blood pressure (SBP), and diastolic blood pressure (DBP) were consistently lower in the IVR group across different stages. Post anesthesia, the IVR group showed notably lower mean SBP and DBP values (p < 0.001). After surgery, the IVR group also showed lower HR (p = 0.01), SBP (p < 0.001), and DBP (p < 0.001) compared to the control group.

CONCLUSIONS

IVR significantly reduced STAI, STAI-S, and MDAS scores and decreased intraoperative pain compared to the control group.

Relations between daily stressful events, exertion, heart rate variability, and thoracolumbar fascia deformability: a case report

BACKGROUND

The posture of performance-oriented sport climbers adapts in a way that likely promotes the development of low back pain. The thoracolumbar fascia, while also contributing to performance, seems to be involved in that process. Furthermore, there has been evidence of the stiffening of the fascial structures in disorders associated with negative affectivity. The study aims to investigate the relationship between the autonomic nervous system and the deformability of the thoracolumbar fascia in a sport climber in a natural setting.

CASE PRESENTATION

Over a 30 day period, a 50-year-old German male reported daily morning resting heart rate variability and daily inventory of stressful events. The thoracolumbar fascia deformation was measured daily using ultrasound in a manual therapy clinic. A time series analysis was performed to detect possible time-delayed relationships between the variables. A cluster analyses revealed two distinguishable heart rate variability clusters (heart rate variability clusters 1 and 2). Both clusters were correlated with thoracolumbar fascia deformation and daily inventory of stressful events. Higher heart rate variability cluster 1 immediately caused lower thoracolumbar fascia deformation. Heart rate variability cluster 1 parameters mediated the effect of daily inventory of stressful events on a decrease in thoracolumbar fascia deformation with a 2-day delay. One heart rate variability cluster 2 parameter mediated the effect of daily inventory of stressful events on an increase in thoracolumbar fascia deformation with a 7-day delay.

CONCLUSION

Heart rate variability cluster 1 values, which probably indicate sympathetic nervous system activity, are directly related to thoracolumbar fascia. Presumably, the sympathetic nervous system mediated the effect of daily inventory of stressful events on a lower thoracolumbar fascia deformation with a 2-day delay, followed by a supercompensation, most likely parasympathetically mediated. Coaches and trainers should be aware of these mechanisms and consider monitoring during training to minimize potential additional risk factors for impaired performance and health.

Training and Game Loads Across Noncongested and Congested Weekly Microcycles During the Regular Season in a Semiprofessional Women's Basketball Team

PURPOSE

To quantify and compare loads encountered in individual training sessions and games during noncongested and congested weeks in semiprofessional women basketball players.

METHODS

Using an observational, longitudinal design, 12 players from the same team had their external (PlayerLoad, relative PlayerLoad, and total and high-intensity inertial movement analysis variables) and internal load (session rating of perceived exertion [sRPE], sRPE-load, percentage of heart rate peak, and modified summated-heart-rate-zones load) monitored across a regular season. Training and game data were categorized into noncongested (0-1 game) and congested weeks (2-3 games). Linear mixed models and Cohen d effect sizes were used for analyses.

RESULTS

Comparisons between training sessions revealed higher (P < .05, d = 1.35-5.33) PlayerLoad, total inertial movement analysis, sRPE, and sRPE-load during training session 1 than training session 2 in congested weeks. Comparisons between training sessions and games revealed higher (P ≤ .001, d = 1.10-1.66) sRPE and sRPE-load during games than training sessions 1 and 2 in noncongested weeks, alongside higher (P ≤ .001, d = 1.87-3.55) sRPE during game 1 than training sessions 1 and 2 in congested weeks. Comparisons between games revealed higher (P < .05, d = 0.57-2.82) loads in game 3 during congested weeks compared with all other games.

CONCLUSIONS

Training appeared to be tapered in congested weeks, likely to account for upcoming increases in game loading, but remained relatively consistent across sessions during noncongested weeks. Individual game loads remained relatively consistent but were noticeably increased when a third game was played in the week.

Evaluation of a passive back-support exoskeleton during in-bed patient handling tasks

This study evaluated the effects of a back-support exoskeleton on the trunk and hip joint angles, lower back muscle activity and heart rate during four patient handling tasks: assisting a patient from sitting to lying, laterally repositioning the patient and turning the patient in two directions. Eight participants performed these tasks with and without the exoskeleton. Results demonstrated a significant reduction in the lower back muscle activity, but less pronounced effects for other tasks involving minimal trunk flexion. Hip flexion angles were reduced for all tasks when the exoskeleton was worn. The amount of reduction in the muscle activity and changes in the trunk and hip angles varied by task. The exoskeleton did not affect the heart rate across all tasks. The exoskeleton appeared to be more effective in tasks requiring substantial trunk flexion, indicating its potential benefits for reducing lower back muscle strain during such activities.

Immersive Virtual Reality Decreases Work Rate and Manipulates Attentional Focus During Self-Regulated Vigorous Exercise

To determine the effect of immersive virtual reality use on finishing time of a vigorous-intensity self-regulated exercise task, and on relevant psychological variables. Healthy untrained adults (N = 21; 10 men/11 women; age = 22.9 ± 7.2 years; BMI = 24.0 ± 4.5 kg/m2) completed 1500-m exercise bouts on a rowing ergometer in a counterbalanced and randomized order, with and without use of a headset-delivered virtual reality fitness program. Heart rate, rating of perceived exertion, affective valence, and attentional focus were collected every 300 m, in addition to finishing time. Data were analyzed with repeated measures as appropriate. Intensity of both exercise bouts was considered vigorous according to heart rate results (>77% maximal heart rate). Finishing time was faster in the control condition (449.57 ± 82.39 s) than in the virtual reality condition (463.00 ± 91.78 s), p = .007. Compared to the control condition, the virtual reality condition was characterized by a more external attentional focus (52.38 ± 18.22 vs. 38.76 ± 17.81, p < .001). No differences were observed for remaining variables as a result of condition (p > .05 for all). When a headset-delivered VR program was used during a self-regulated vigorous-intensity exercise task, participants were 13.6 seconds (~3%) slower than in a control condition. Attentional focus was manipulated to be more external with VR use, which may have ultimately distracted from the exercise objective. Recommendations for selecting an appropriate virtual reality experience for a given exercise task are discussed.

Glycaemic Response to Acute Aerobic and Anaerobic Exercise Performed in the Morning or Afternoon in Healthy Subjects: A Crossover Trial

BACKGROUND

The regular practice of physical activity is considered a health promoter and appears to be one of the main contributors to the prevention of chronic diseases. However, the potential effects of exercise on health depending on the time of day at which it is performed have not yet been fully elucidated.

OBJECTIVES

To evaluate the effect of physical exercise (aerobic or anaerobic) and chronobiology (morning or afternoon) on the glycemic metabolism of healthy subjects.

METHODS

Healthy subjects participated in aerobic or anaerobic physical exercise sessions, either in the morning or in the afternoon. Blood was drawn from the subjects before, at the end of the exercise and 2 hours after the end of the exercise. Glycemic parameters were analyzed at these time points. A general linear model test was performed after verifying the normal distribution of the raw data (as assessed by the Shapiro-Wilk test) or after a logarithmic/square root transformation, considering aerobic or anaerobic exercise and morning or afternoon exercise as independent variables.

RESULTS

Twenty-three subjects (14 women and 9 men) were included in the study. The rate of change in glucose levels was significantly higher at the end of anaerobic exercise compared to aerobic exercise (1.19 ± 0.04 vs. 0.98 ± 0.02, respectively), with a more pronounced decrease in insulin and C-peptide levels following aerobic exercise. In addition, the increase of glucose was higher after the exercise in the morning compared with the afternoon (1.14 ± 0.03 vs. 1.03 ± 0.03, respectively).

CONCLUSIONS

The type of exercise and chronobiology influence short-term glucose metabolism.

Virtual Reality Exercise with Autonomy Support Increases Positive Affect During Time Trial Exercise

Background: Being able to choose elements of an exercise session, known as autonomy support, improves motor performance and psychological responses. Virtual reality (VR) programs provide many options for embedding autonomy support in exercise sessions. The purpose of this study was to investigate the effects of autonomy support in a VR setting on physiological and psychological responses to self-regulated rowing exercise. Methods: Using a repeated-measures crossover design, healthy untrained men and women (N = 20, age = 23.0 ± 7.4) completed exercise sessions on a rowing ergometer coupled with a head-mounted immersive VR application. In the Choice condition, participants chose the virtual environment, and in the Control condition, the environment was assigned to the participant. Participants were instructed to complete 1500 m as quickly as possible in both conditions, while ratings of perceived exertion, affective valence, and heart rate were recorded throughout the trials. Finishing time and remembered pleasure were assessed at the end of each session. Repeated-measures analyses with an alpha level of 0.05 were used for all variables as appropriate, with Bonferroni adjustments applied for any post hoc tests. Results: There was a main effect of condition on affective valence which was higher in Choice (2.07 ± 1.67) than Control (1.64 ± 2.12, P = 0.03, η2 = 0.22). No other differences were detected between conditions for finishing time or the remaining variables. Conclusion: During self-regulated exercise accompanied by an immersive VR application, being able to choose the virtual environment oneself leads to a more positive affective state without compromising exercise effort, physiological strain, or performance.

Correlation properties of heart rate variability for exercise prescription during prolonged running at constant speeds: A randomized cross-over trial

The study explores the validity of the nonlinear index alpha 1 of detrended fluctuation analysis (DFAa1) of heart rate (HR) variability for exercise prescription in prolonged constant load running bouts of different intensities. 21 trained endurance athletes (9 w and 12 m) performed a ramp test for ventilatory threshold (vVT1 and vVT2) and DFAa1-based (vDFAa1-1 at 0.75 and vDFAa1-2 at 0.5) running speed detection as well as two 20-min running bouts at vDFAa1-1 and vDFAa1-2 (20-vDFAa1-1 and 20-vDFAa1-2), in which HR, oxygen consumption (VO2), respiratory frequency (RF), DFAa1, and blood lactate concentration [La-] were assessed. 20-vDFAa1-2 could not be finished by all participants (finisher group (FG), n = 15 versus exhaustion group (EG), n = 6). Despite similar mean external loads of vDFAa1-1 (10.6 ± 1.9 km/h) and vDFAa1-2 (13.1 ± 2.4 km/h) for all participants compared to vVT1 (10.8 ± 1.7 km/h) and vVT2 (13.2 ± 1.9 km/h), considerable differences were present for 20-vDFAa1-2 in EG (15.2 ± 2.4 km/h). 20-vDFAa1-1 and 20-DFAa1-2 yielded significant differences in FG for HR (76.2 ± 5.7 vs. 86.4 ± 5.9 %HRPEAK), VO2 (62.1 ± 5.0 vs. 77.5 ± 8.6 %VO2PEAK), RF (40.6 ± 11.3 vs. 46.1 ± 9.8 bpm), DFA-a1 (0.86 ± 0.23 vs. 0.60 ± 0.15), and [La-] (1.41 ± 0.45 vs. 3.34 ± 2.24 mmol/L). Regarding alterations during 20-vDFAa1-1, all parameters showed small changes for all participants, while during 20-vDFAa1-2 RF and DFAa1 showed substantial alterations in FG (RF: 15.6% and DFAa1: -12.8%) and more pronounced in EG (RF: 20.1% and DFAa1: -35.9%). DFAa1-based exercise prescription from incremental testing could be useful for most participants in prolonged running bouts, at least in the moderate to heavy intensity domain. In addition, an individually different increased risk of overloading may occur in the heavy to severe exercise domains and should be further elucidated in the light of durability and decoupling assessment.

A Systematic Review on the Use of Consumer-Based ECG Wearables on Cardiac Health Monitoring

This systematic review aims to summarize the consumer wearable devices used for collecting ECG signals, explore the models or algorithms employed in diagnosing and preventing heart-related diseases through ECG analysis, and discuss the challenges and future work related to adopting health monitoring using consumer wearable devices. Following the PRISMA method, we identified and reviewed 102 relevant papers from PubMed, IEEE, and Web of Science databases, covering the period from May 2013 to May 2023. This review comprehensively summarizes consumer wearable devices with ECG functions, available ECG datasets, and various algorithms for detecting cardiac diseases and monitoring long-term health. It also discusses the integration challenges and future directions in cardiac health monitoring. The results highlight a preference for deep learning algorithms, such as Convolutional Neural Networks (CNNs) and their variations, in analyzing ECG data due to the ability to automate feature extraction and reduce memory requirements. The review also discusses potential limitations of the current literature, including lack of reasoning and comparison of algorithms and limited data generalizability. By analyzing the current literature, this review provides an overview of state-of-the-art technologies, identifies key findings, and suggests potential avenues for future research and implementation.

Assessment of Physiological Signals from Photoplethysmography Sensors Compared to an Electrocardiogram Sensor: A Validation Study in Daily Life

Wearables with photoplethysmography (PPG) sensors are being increasingly used in clinical research as a non-invasive, inexpensive method for remote monitoring of physiological health. Ensuring the accuracy and reliability of PPG-derived measurements is critical, as inaccuracies can impact research findings and clinical decisions. This paper systematically compares heart rate (HR) and heart rate variability (HRV) measures from PPG against an electrocardiogram (ECG) monitor in free-living settings. Two devices with PPG and one device with an ECG sensor were worn by 25 healthy volunteers for 10 days. PPG-derived HR and HRV showed reasonable accuracy and reliability, particularly during sleep, with mean absolute error < 1 beat for HR and 6-15 ms for HRV. The relative error of HRV estimated from PPG varied with activity type and was higher than during the resting state by 14-51%. The accuracy of HR/HRV was impacted by the proportion of usable data, body posture, and epoch length. The multi-scale peak and trough detection algorithm demonstrated superior performance in detecting beats from PPG signals, with an F1 score of 89% during sleep. The study demonstrates the trade-offs of utilizing PPG measurements for remote monitoring in daily life and identifies optimal use conditions by recommending enhancements.

Cardiovascular handgrip responses during treadmill exercise: randomized pilot trial

Background

The isometric exercise performed using the handgrip (HG) acutely promotes elevation of systolic blood pressure (SBP) and diastolic blood pressure (DBP), and in a non-consensual manner among articles elevation or maintenance of heart rate (HR). Currently, although there is a vast literature on the hemodynamic effects of interval training and isometric exercise with HG alone, there is still no consistent evidence of such adjustments occurring in the association between the two. Therefore, the objective of this study was to describe the acute hemodynamic responses found only during interval training and when combined with isometric contraction with HG.

Methods

This is a pilot study of a crossover clinical trial. Seven male volunteers, aged 24±3.9 years, underwent three protocols on an ergometric treadmill, with a 3-minute warm-up at 30% of heart rate reserve (HRR), four sprints 2 minutes at 50% HRR and active intervals at the same speed as the warm-up. Randomization was carried out in a simple random manner. The protocols were classified according to the use of HG during sprints, as follows: PI = without HG; PII = HG 30% of handgrip strength (HGS) and PIII = 60% of HGS). Variations (Δ) in HR, double product (DP), SBP and DBP were evaluated.

Results

The presence of HG did not change HR behavior, but it increased DP (PI: 10,472±2,539 vs. PII: 12,217±1,933 vs. PIII: 13,369±3,089) through SBP, which in PI had a plateau behavior of 15±22.2 mmHg, while PII varied with an average of 41±12.2 mmHg and PIII 47±11.1 mmHg, in the 4th sprint. DBP fell in PI with 12±13.2 mmHg, while PII and PIII showed an drop of 0±19.6 and 6±13.0 mmHg in the last sprint, respectively.

Conclusions

The use of HG during interval training directly modulates hemodynamic variables, promoting an increase in SBP elevation, attenuation of the drop in DBP and an increase in DP, without an increase in HR.

Trial Registration

RBR-78fhyrf. Available in https://ensaiosclinicos.gov.br/rg/RBR-78fhyrf.

Implementation of a mixed-methods heat acclimation programme in a professional soccer referee before the 2022 FIFA world cup in Qatar: a case study

Objectives

This case study reports the real-world practicalities of implementing a mixed-methods heat acclimation (HA) programme before the 2022 FIFA World Cup.

Methods

One male English soccer referee (age: 44 years; height: 1.82 m; body mass: 76.0 kg) who had officiated professionally for over 17 years and had over 10 years' experience officiating in European and international matches undertook an 11-session HA programme over 22 days. On days 1 and 22, a 30 min fixed-intensity heat tolerance test (9 km.h-1, 2% gradient, 40°C, 40% relative humidity) was performed, and physiological and perceptual responses were measured. A mixed-methods HA approach was used, including environmental chamber isothermic training, post-temperate training saunas and hot water immersion.

Results

Compared with the pre-test, peak core temperature reduced by 0.40°C (38.4 vs 38.0°C; minimal detectable change (MDC) = 0.34°C), peak skin temperature reduced by 0.5°C (36.7 vs 36.2°C; MDC=0.28°C) and peak heart rate reduced by 5 b·min-1 (167 vs. 162 b·min-1; MDC=4 b·min-1) in the post-test. In the post-test, the sweat rate increased by 17% (1.94 vs 2.27 L.h-1; MDC=0.42 L.h-1). Peak thermal sensation (7 = 'hot') and the rating of perceived exertion (3 = 'moderate') were unchanged between the tests. However, peak thermal comfort (3 = 'slightly uncomfortable' vs 2 = 'uncomfortable') was rated lower in the post-test.

Conclusion

The HA programme elicited positive physiological but indifferent perceptual responses, highlighting that mixed-methods HA can be implemented when a referee still has officiating, travel and training responsibilities during the HA window.

The Dynamics of Heart Rate Asymmetry and Situational Sleepiness from Evening to Night: The Role of Daytime Sleepiness

The relationship between daytime sleepiness and heart rate asymmetry (HRA) during the transition from evening to night is crucial for understanding autonomic regulation and its implications for alertness. This study aims to investigate how daytime sleepiness influences HRA dynamics from evening to night and how situational sleepiness correlates with HRA metrics. HRA metrics were calculated at 8 P.M., 9 P.M., and 10 P.M. in 50 participants, categorized into 'Lower Normal' and 'Higher Normal' daytime sleepiness groups based on Epworth Sleepiness Scale (ESS) scores. Situational sleepiness was assessed using the Karolinska Sleepiness Scale (KSS) and Stanford Sleepiness Scale (SSS). The results demonstrated that individuals with 'Higher Normal' daytime sleepiness exhibited lower HRA metrics at 10 P.M. compared to those with 'Lower Normal' daytime sleepiness, supporting the suggestion that higher daytime sleepiness correlates with reduced parasympathetic activity and diminished autonomic responsiveness. Significant negative correlations between situational sleepiness and HRA metrics were observed in the 'Higher Normal' group, particularly with the SSS. Therefore, increased daytime sleepiness affects HRA dynamics by decreasing parasympathetic activity and altering autonomic regulation at the beginning of the biological night (10 P.M.). These findings suggest potential applications for enhancing drowsiness detection and managing fatigue in safety-critical environments.

Feasibility of Wearable Sensors to Assess Cognitive Load During Clinical Performance: Lessons Learned and Blueprint for Success

INTRODUCTION

Cognitive load (CogL) is increasingly recognized as an important resource underlying operative performance. Current innovations in surgery aim to develop objective performance metrics via physiological monitoring from wearable digital sensors. Surgeons have access to consumer technology that could measure CogL but need guidance regarding device selection and implementation. To realize the benefits of surgical performance improvement these methods must be feasible, incorporating human factors usability and design principles. This paper aims to evaluate the feasibility of using wearable sensors to assess CogL, identify the benefits and challenges of implementing devices, and develop guidance for surgeons planning to implement wearable devices in their research or practice.

METHODS

We examined the feasibility of wearable sensors from a series of empirical studies that measured aspects of clinical performance relating to CogL. Across four studies, 84 participants and five sensors were involved in the following clinical settings: (i) real intraoperative surgery; (ii) simulated laparoscopic surgery; and (iii) medical team performance outside the hospital.

RESULTS

Wearable devices worn on the wrist and chest were found to be comfortable. After a learning curve, electrodermal activity data were easily and reliably collected. Devices using photoplethysmography to determine heart rate variability were significantly limited by movement artifact. There was variable success with electroencephalography devices regarding connectivity, comfort, and usability.

CONCLUSIONS

It is feasible to use wearable sensors across various clinical settings, including surgery. There are some limitations, and their implementation is context and device dependent. To scale sensor use in clinical research, surgeons must embrace human factors principles to optimize wearability, usability, reliability, and data security.

The Validity of Apple Watch Series 9 and Ultra 2 for Serial Measurements of Heart Rate Variability and Resting Heart Rate

The widespread use of wearable devices has enabled continuous monitoring of biometric data, including heart rate variability (HRV) and resting heart rate (RHR). However, the validity of these measurements, particularly from consumer devices like Apple Watch, remains underexplored. This study aimed to validate HRV measurements obtained from Apple Watch Series 9 and Ultra 2 against the Polar H10 chest strap paired with the Kubios HRV software, which together served as the reference standard. A prospective cohort of 39 healthy adults provided 316 HRV measurements over a 14-day period. Generalized Estimating Equations were used to assess the difference in HRV between devices, accounting for repeated measures. Apple Watch tended to underestimate HRV by an average of 8.31 ms compared to the Polar H10 (p = 0.025), with a mean absolute percentage error (MAPE) of 28.88% and a mean absolute error (MAE) of 20.46 ms. The study found no significant impact of RHR discrepancies on HRV differences (p = 0.156), with RHR showing a mean difference of -0.08 bpm, an MAPE of 5.91%, and an MAE of 3.73 bpm. Equivalence testing indicated that the HRV measurements from Apple Watch did not fall within the pre-specified equivalence margin of ±10 ms. Despite accurate RHR measurements, these findings underscore the need for improved HRV algorithms in consumer wearables and caution in interpreting HRV data for clinical or performance monitoring.

Remote fitness assessment in younger and middle-aged to older adults: a comparison between laboratory- and videoconference-based assessment of selected measures of physical and cognitive fitness

BACKGROUND

Digital technologies can play an important role in improving the limited accessibility of healthcare services in rural regions (e.g., via remote assessment). However, whether remote fitness assessments (RFA) of selected physical and cognitive fitness parameters are feasible both in younger and older persons and whether they can reproduce laboratory tests needs yet to be established. Thus, this study aimed to address this knowledge gap by investigating the feasibility, and reproducibility of RFA in younger and middle-aged to older adults (MOA).

METHODS

A total of 31 younger adults and 32 MOAs participated in this study. At an interval of seven days, laboratory-based and remote assessments (via videoconferencing software) were conducted which included the quantification of the following parameters: (i) measurement of heart rate variability [HRV]; followed by (ii) cognitive testing to examine the level of attention, executive functions (oral Trail Making Test [A and B]), working memory, verbal short-term memory (digit span memory test and word list test (immediate recall)) and episodic memory (word list test (delayed recall)); followed by (iii) physical fitness assessments including performance tests of balance (balance test), functional strength ability of the lower limbs (5-time-sit-to-stand-test) and endurance capacity (3-min step test). Parameters of absolute and relative reliability were determined to assess the reproducibility of the laboratory-based and remote assessments.

RESULTS

The selected physical and cognitive fitness parameters showed moderate to excellent relative reliability (intraclass correlation coefficient [ICC] = 0.52-0.95). The parameters of absolute reliability (Bland-Altman plot and standard error of measurement [SEM]) provide evidence for good reproducibility of HRV parameters and measures of physical fitness, whereas measures of cognitive fitness showed moderate to good reproducibility. On a descriptive level, the absolute and relative reliability of the selected measures of physical and cognitive fitness did not vary as a function of participants' age.

CONCLUSION

Our results suggest that RFA of selected measures of physical and cognitive fitness is feasible and reproduces corresponding laboratory results to a moderate to excellent level in both younger adults and MOA. Data showed that the reproducibility of laboratory-based and remote assessments is not influenced by the age of the participants. These findings support the use of digital technologies to improve the accessibility of healthcare services (e.g., in remote areas). However, as the reproducibility varies considerably across the different parameters, further studies are needed to evaluate the effects of an optimised standardisation of the remote assessments and confounding factors.

Best-Corrected Visual Acuity Quantitative Prediction for Cataract Patients: AI-Assisted Clinical Diagnostics Facilitation via the Inverse Problem Algorithm

Objective: This study provided a quantitative prediction of best-corrected visual acuity (BCVA) for cataract patients using the inverse problem algorithm (IPA) technique earlier proposed by the authors. Methods: To this end, seven risk factors (age, BMI, MAP, IOP, HbA1c, LDL-C, and gender) were linked by a semi-empirical formula by normalizing each factor into a dimensionless range of -1.0 to +1.0. The adopted inverse problem algorithm (IPA) technique was run via a self-developed program in STATISTICA 7.0, featuring a 29-term nonlinear equation considering seven risk factors, cross-interaction between various pairs of factors, and one constant term [7 + (7 × 6)/2 + 1 = 29]. The IPA neglected quadratic, triple, or quadruple factors' cross-interactions. This study used a dataset of 632 cataract patients to attain a reliable BCVA prediction with a variance of 0.929. A verification dataset of 160 patients with similar symptoms was used to verify this approach's feasibility, reaching a good correlation with R2 = 0.909. Results: The verification group's derived average AT (agreement) (9.12 ± 27.00%) indicated a slight deviation between the theoretical prediction and practical BCVA. The significant factors were age, body mass index (BMI), and intraocular pressure (IOP), whereas mean arterial pressure (MAP), hemoglobin A1c (HbA1c), low-density-lipoprotein cholesterol (LDL-C), and gender insignificantly contributed to BCVA. Conclusions: The proposed approach is instrumental in AI-assisted clinical diagnosis, yielding robust BCVA predictions for individual cataract patients based on their biological indices before the ophthalmological examination procedure.

Pilot turning behavior cognitive load analysis in simulated flight

Background

To identify the cognitive load of different turning tasks in simulated flight, a flight experiment was designed based on real "preliminary screening" training modules for pilots.

Methods

Heart Rate Variability (HRV) and flight data were collected during the experiments using a flight simulator and a heart rate sensor bracelet. The turning behaviors in flight were classified into climbing turns, descending turns, and level flight turns. A recognition model for the cognitive load associated with these turning behaviors was developed using machine learning and deep learning algorithms.

Results

pnni_20, range_nni, rmssd, sdsd, nni_20, sd1, triangular_index indicators are negatively correlated with different turning load. The LSTM-Attention model excelled in recognizing turning tasks with varying cognitive load, achieving an F1 score of 0.9491.

Conclusion

Specific HRV characteristics can be used to analyze cognitive load in different turn-ing tasks, and the LSTM-Attention model can provide references for future studies on the selection characteristics of pilot cognitive load, and offer guidance for pilot training, thus having significant implications for pilot training and flight safety.

Effects of Vibroacoustic Stimulation on Psychological, Physiological, and Cognitive Stress

Global stress is widespread in today's post-pandemic world of political and economic uncertainty. Vibroacoustic technology is a vibrotactile intervention with multiple uses, but its impact on stress lacks interpretation. This research assessed if the vibroacoustic technology of a Vibroacoustic Sound Massage (VSM) can reduce psychological, physiological, and cognitive stress. The Perceived Stress Scale (PSS-10) and electrocardiogram (ECG) and electroencephalogram (EEG) biosignals were used to quantify results. Participants were divided into Low-Stress and High-Stress groups. The ECG results show VSM increased parasympathetic activity for all participants, with the Low-Stress group being more affected. The EEG results indicate increased concentration, reduced arousal, and increased relaxation, with participant well-being non-significantly affected, though variability in this metric was homogenised after VSM. Together, these results validate VSM as an effective support tool for stress management; however, further research is required.

Effect of high-intensity interval training and moderate-intensity continuous training on blood lactate clearance after high-intensity test in adult men

This study compared the effects of High-intensity interval training (HIIT) and moderate-intensity continuous training (MICT) on blood lactate clearance. 21 adult males were equally and randomly assigned to the HIIT and MICT groups, and completed 8 weeks of training. Before the training intervention, after 4 weeks and 8 weeks of training, all subjects were tested for blood lactate levels between 0 and 55 min after the same high-intensity test. The results show that after 8 weeks, blood lactate levels were significantly lower than pre-tests in both the HIIT and MICT groups at "0-55 min" after high-intensity test (p < 0.05), and the blood lactate clearance percentage at15-min and 30-min in both groups were significantly higher than the pre-tests (P < 0.01). The blood lactate levels in the HIIT group were significantly lower than those in the MICT group at 15 min and 30 min after test (P < 0.05), and the blood lactate clearance percentage at 30 min in the HIIT group was significantly higher than those in the MICT group (P < 0.05). In conclusion, both HIIT and MICT enhance blood lactate clearance in adult males post high-intensity test, with HIIT demonstrating superior effectiveness, making it a viable alternative to MICT.

Validation of "CENTR(AR)" walking trails: Different field criteria do not lead to different physical activity intensities in people with COPD

BACKGROUND

Validating walking trails is essential to promote physical activity (PA) safely and confidently in people with COPD.

OBJECTIVES

We aimed to validate predetermined light, moderate, and vigorous intensities of walking trails in people with COPD.

METHODS

This cross-sectional study included individuals with COPD walking in predetermined light, moderate and vigorous intensity trails. Activity intensity and volume outcomes were collected. Dyspnoea and fatigue (modified Borg scale), energy expenditure (EE, Sensewear), heart rate (HR, HR monitor), time spent in different PA intensities, and cadence (ActiGraph) were recorded and used to classify PA intensity.

RESULTS

Twenty people with COPD [71(7) years, 80 % male, FEV1%predicted 65.6(11.6)] were included. Fatigue differed significantly between light and moderate [3.0(2.0;4.0) vs 3.4(2.5;4.5), p = 0.01], but not vigorous (3.5[2.5-4.0]) tracks. Dyspnoea [2.3(1.5) vs 2.7(1.6) vs 2.6(1.4)], EE [5.1(0.8) vs 4.9(0.5) vs 4.6(0.8) METs], HR [92.5(11.1) vs 93.7(18.6) vs 95.4(15.0) beats/min] and cadence [115.1(104.0;120.3) vs 104.7(99.6;117.6) vs 111.2(99.9;118.5) steps/min] were similar across trails (p > 0.05). Time spent in light and moderate PA, EE volume, walking time, and step count increased along with the proposed intensity levels (p < 0.01). Walking trails were categorised as moderate intensity in most participants.

CONCLUSION

Walking trails were safe and valid for practising moderate-intensity PA in people with COPD. Participants adjusted their physiological responses and perceived symptoms to match a moderate intensity.

Effects of a tailor-made yoga program on upper limb function and sleep quality in women with breast cancer: A pilot randomized controlled trial

Purpose

Upper limb dysfunction and sleep disturbance are common and serious health problems in women with breast cancer. Yoga is a mind-body intervention which is shown to improve physical and psychological health. The aim of this study is to evaluate the effectiveness of a tailor-made yoga program on upper limb function and sleep quality in women with breast cancer.

Methods

A pilot randomized controlled trial (RCT) study design was used. Participants were randomly allocated to either the yoga intervention group (YG; eight weekly 60-min group-based yoga sessions) or the wait-list control group (CG). The primary outcome measures were upper limb function and sleep quality, which were assessed by the self-reported questionnaires - the shortened version of the Disabilities of the Arm, Shoulder and Hand (QuickDASH) and the Pittsburgh Sleep Quality Index (PSQI), respectively. The secondary outcome measures were upper limb muscle strength and mobility, heart rate variability (HRV), anxiety and depression, fatigue, and health-related quality of life. All participants underwent assessment at four time-points (baseline, mid-intervention, post-intervention, and 1-month follow-up). The effectiveness of the intervention was tested by two-way mixed-design repeated-measures analysis of covariance.

Results

For the primary outcomes, there was no significant between-group difference in the upper limb function. The YG demonstrated significantly shorter sleep latency and higher HRV, and less sleep disturbance than the CG at post-intervention, and 1-month follow-up, respectively. For the secondary outcomes, the YG demonstrated significantly improved shoulder muscle strength and arm symptoms compared to the CG from mid-intervention until the 1-month follow-up.

Conclusion

This pilot trial revealed that the yoga program was feasible to be implemented for women with primary stage breast cancer. Although yoga was not found to be effective in improving the upper limb function, it improved sleep latency, HRV, shoulder muscle strength and arm symptoms of women with breast cancer.

Physiological and perceptual responses of wearing a dryrobe for rewarming after passive cold-water immersion in men

Objectives

To investigate the physiological and perceptual responses to wearing a dryrobe for rewarming after passive cold-water immersion (CWI).

Methods

15 unhabituated healthy Caucasian men (age: 28.9 (5.4) years) attended the laboratory on three occasions and performed passive CWI (14°C) for 30 min followed by 15 min of rewarming wearing either a dryrobe, towel or foil blanket while positioned in front of fans replicating a 10 mph wind. Physiological (deep body temperature, skin temperature and heart rate) and perceptual (thermal sensation and thermal comfort) variables were measured.

Results

At 15 min post-immersion, deep body temperature was higher in the dryrobe condition (mean: 37.09 (SD: 0.49)°C) compared with the foil blanket (36.98 (0.64)°C) and towel (36.99 (0.49)°C) (p<0.001). On average across the 15 min post-immersion period, the dryrobe increased skin temperature to the greatest degree (18.9 (1.0)°C, +2.4°C), compared with the foil blanket (18.1 (1.2)°C, +1.8°C, p=0.034) and the towel (16.6 (1.2)°C, +1.3°C, p<0.001). Average heart rate across the 15 min post-immersion period was lower when wearing the dryrobe (dryrobe: 74 (10) b.min-1, foil blanket: 78 (6) b.min-1 and towel: 82 (14) b.min-1 (p=0.015). Thermal sensation and thermal comfort were higher at all post-immersion time points in the dryrobe compared with the foil blanket and towel.

Conclusions

During the rewarming period following CWI, physiological and perceptual responses are improved when wearing clothing that combines an insulative layer with a vapour barrier, such as the dryrobe compared with a towel or foil blanket. This might have future implications for safety recommendations during rewarming.

Influence of an inspiratory muscle fatigue protocol on healthy youths on respiratory muscle strength and heart rate variability. A randomized controlled trial

Introduction: Inspiratory muscle fatigue has been shown to have effects on the autonomic nervous system and physical condition. This study aimed to evaluate the influence of an inspiratory muscle fatigue protocol on respiratory muscle strength and heart rate variability in healthy youths. Materials and Methods: A randomized controlled clinical trial, employing double-blinding, was conducted with twenty-seven participants aged 18-45 years, non-smokers and engaged in sports activity at least three times a week for a minimum of 1 year. Participants were randomly assigned to three groups: Inspiratory Muscle Fatigue group, Activation group, and Control group. Measurements of heart rate variability, diaphragmatic ultrasound, and maximum inspiratory pressure were taken at two stages: before the intervention and immediately after treatment. Results: In our results with respect to baseline to post-treatment, the inspiratory muscle fatigue group showed lower values in the Sniff contraction velocity variable (10.96 cm/s ± 1.99-8.34 cm/s ± 1.23; p < 0.01) and higher values in the activation group (10.59 cm/s ± 0.89-12.66 cm/s ± 1.15; p < 0.01) with respect to the control group (10.27 cm/s ± 1.48-9.97 cm/s ± 1.42). On the other hand, the inspiratory muscle fatigue group showed higher values in the Low frequency variable (49.37 n.u. ± 13.91 to 69.48 n.u. ± 8.22; p < 0.01) and lower values in the activation group (57.92 n.u. ± 8.37 to 41.59 n.u. ± 11.21; p < 0.01) with respect to the control group (50.83 n.u. ± 17.30 to 52.10 n.u. ± 20.64). Additionally, significant correlations were found between respiratory variables and heart rate variability variables. Conclusion: Acute fatigue of the inspiratory musculature appears to negatively impact heart rate variability and inspiratory muscle strength in healthy youths. Clinical Trial Registration: https://clinicaltrials.gov/study/NCT06278714; Identifier: NCT06278714.

Exploring immediate cardiorespiratory responses: low-intensity blood flow restricted cycling vs. moderate-intensity traditional exercise in a randomized crossover trial

PURPOSE

Blood-flow restriction (BFR) endurance training may increase endurance performance and muscle strength similar to traditional endurance training while requiring a lower training intensity. We aimed to compare acute cardiorespiratory responses to low-intensity interval exercise under BFR with moderate-intensity traditional interval exercise (TRA).

METHODS

We conducted a randomized crossover study. The protocol involved three cycling intervals interspersed with 1 min resting periods. With a 48-h washout period, individuals performed the protocol twice in random order: once as BFR-50 (i.e., 50% incremental peak power output [IPPO] and 50% limb occlusion pressure [LOP]) and once as TRA-65 (65% IPPO without occlusion). TRA-65 intervals lasted 2 min, and time-matched BFR-50 lasted 2 min and 18 s. Respiratory parameters were collected by breath-by-breath analysis. The ratings of perceived breathing and leg exertion (RPE, 0 to 10) were assessed. Linear mixed models were used for analysis.

RESULTS

Out of the 28 participants initially enrolled in the study, 24 healthy individuals (18 males and 6 females) completed both measurements. Compared with TRA-65, BFR-50 elicited lower minute ventilation (VE, primary outcome) (-3.1 l/min [-4.4 to -1.7]), oxygen consumption (-0.22 l/min [-0.28 to -0.16]), carbon dioxide production (-0.25 l/min [-0.29 to -0.20]) and RPE breathing (-0.9 [-1.2 to -0.6]). RPE leg was significantly greater in the BFR-50 group (1.3 [1.0 to 1.7]).

CONCLUSION

BFR endurance exercise at 50% IPPO and 50% LOP resulted in lower cardiorespiratory work and perceived breathing effort compared to TRA at 65% IPPO. BFR-50 could be an attractive alternative for TRA-65, eliciting less respiratory work and perceived breathing effort while augmenting perceived leg muscle effort.

TRIAL REGISTRATION

NCT05163600; December 20, 2021.

Heart rate-related physiological changes induced by classical music-elicited emotions do not underlie alterations in healthy adults' ankle joint target-matching strategy

Emotions have the potential to modulate human voluntary movement by modifying muscle afferent discharge which in turn may affect kinesthetic acuity. We examined if heart rate (HR)-related physiological changes induced by music-elicited emotions would underlie alterations in healthy young adults' ankle joint target-matching strategy quantified by joint position sense (JPS). Participants (n = 40, 19 females, age = 25.9 ± 2.9 years) performed ipsilateral-, and contralateral ankle target-matching tasks with their dominant and non-dominant foot using a custom-made foot platform while listening to classical music pieces deemed to evoke happy, sad, or neutral emotions (each n = 10). Participants in the 4th group received no music during the task. Absolute (ABS), constant (CONST), and variable (VAR) target-matching errors and HR-related data were analyzed. Participants performed the contralateral target-matching task with smaller JPS errors when listening to sad vs. happy music (ABS: p < 0.001, d = 1.6; VAR: p = 0.010, d = 1.2) or neutral (ABS: p < 0.001, d = 1.6; VAR: p < 0.001, d = 1.4) music. The ABS (d = 0.8) and VAR (d = 0.3) JPS errors were lower when participants performed the task with their dominant vs. non-dominant foot. JPS errors were also smaller during the ipsilateral target-matching task when participants (1) listened to sad vs. neutral (ABS: p = 0.007, d = 1.2) music, and (2) performed the target-matching with their dominant vs. non-dominant foot (p < 0.001, d = 0.4). Although emotions also induced changes in some HR-related data during the matching conditions, i.e., participants who listened to happy music had lower HR-related values when matching with their non-dominant vs. dominant foot, these changes did not correlate with JPS errors (all p > 0.05). Overall, our results suggest that music-induced emotions have the potential to affect target-matching strategy and HR-related metrics but the changes in HR-metrics do not underlie the alteration of ankle joint target-matching strategy in response to classical music-elicited emotions.

Day-to-day reliability of basal heart rate and short-term and ultra short-term heart rate variability assessment by the Equivital eq02+ LifeMonitor in US Army soldiers

INTRODUCTION

The present study determined the (1) day-to-day reliability of basal heart rate (HR) and HR variability (HRV) measured by the Equivital eq02+ LifeMonitor and (2) agreement of ultra short-term HRV compared with short-term HRV.

METHODS

Twenty-three active-duty US Army Soldiers (5 females, 18 males) completed two experimental visits separated by >48 hours with restrictions consistent with basal monitoring (eg, exercise, dietary), with measurements after supine rest at minutes 20-21 (ultra short-term) and minutes 20-25 (short-term). HRV was assessed as the SD of R-R intervals (SDNN) and the square root of the mean squared differences between consecutive R-R intervals (RMSSD).

RESULTS

The day-to-day reliability (intraclass correlation coefficient (ICC)) using linear-mixed model approach was good for HR (0.849, 95% CI: 0.689 to 0.933) and RMSSD (ICC: 0.823, 95% CI: 0.623 to 0.920). SDNN had moderate day-to-day reliability with greater variation (ICC: 0.689, 95% CI: 0.428 to 0.858). The reliability of RMSSD was slightly improved when considering the effect of respiration (ICC: 0.821, 95% CI: 0.672 to 0.944). There was no bias for HR measured for 1 min versus 5 min (p=0.511). For 1 min measurements versus 5 min, there was a very modest mean bias of -4 ms for SDNN and -1 ms for RMSSD (p≤0.023).

CONCLUSION

When preceded by a 20 min stabilisation period using restrictions consistent with basal monitoring and measuring respiration, military personnel can rely on the eq02+ for basal HR and RMSSD monitoring but should be more cautious using SDNN. These data also support using ultra short-term measurements when following these procedures.

Reliability of an "At-Home" Method for Monitoring Resting and Reactive Autonomic Nervous System Activity in Children: A Pilot Study

BACKGROUND

Heart rate variability (HRV), an index of the functional status of the autonomic nervous system (ANS), provides an opportunity for early detection of ANS dysfunction. Lower resting, vagally related HRV parameters are associated with increased risk of physical and mental illness. External factors influencing the ANS, such as the testing environment, may impact the interpretation of HRV. This study's main aim was to determine the reliability of HRV resting and reactivity tests performed at home with children aged 4-9 years.

METHODS

Fourteen healthy children (female n = 8) aged 6.8 ± 1.5 years participated. Two HRV tests were performed at home via online supervision 7 days apart using a Polar H10 heart rate monitor. The absolute and relative reliability of the pre-exercise resting (5 min) and sub-maximal exercise step test recovery (4 × 30 s segments) HRV time and frequency domains were calculated.

RESULTS

The Pearson correlation coefficients for day 1 versus day 7 for the vagal activity HRV domains (RMSSD log) at rest and in the first 30 s and 30-60 s of recovery indicated good-to-excellent relative reliability (r > 0.8, p < 0.01). Absolute reliability was moderate for the resting RMSSD log, with a coefficient of variation (CV) of 5.2% (90% CI: 3.9, 7.8%), high for the first 30 s of standing recovery, with a CV of 10.7% (90% CI: 8.2, 15.7%), and moderate for 30-60 s of recovery, with a CV of 8.7% (90% CI: 6.6, 12.9%).

CONCLUSIONS

The findings of this pilot study indicate that the resting and exercise recovery HRV measures of vagal activity can be measured reliably at home in children. This represents a novel "at-home" protocol for monitoring ANS health and development in children.

Gait and heart rate: do they measure trait or state physical fatigue in people with multiple sclerosis?

BACKGROUND

Trait and state physical fatigue (trait-PF and state-PF) negatively impact many people with multiple sclerosis (pwMS) but are challenging symptoms to measure. In this observational study, we explored the role of specific gait and autonomic nervous system (ANS) measures (i.e., heart rate, HR, r-r interval, R-R, HR variability, HRV) in trait-PF and state-PF.

METHODS

Forty-eight pwMS [42 ± 1.9 years, 65% female, EDSS 2 (IQR: 0-5.5)] completed the Timed Up and Go test (simple and with dual task, TUG-DT) and the 6-min walk test (6MWT). ANS measures were measured via a POLAR H10 strap. Gait was measured using inertial-measurement units (OPALs, APDM Inc). Trait-PF was evaluated via the Modified Fatigue Impact Scale (MFIS) motor component. State-PF was evaluated via a Visual Analog Scale (VAS) scale before and after the completion of the 6MWT. Multiple linear regression models identified trait-PF and state-PF predictors.

RESULTS

Both HR and gait metrics were associated with trait-PF and state-PF. HRV at rest was associated only with state-PF. In models based on the first 3 min of the 6MWT, double support (%) and cadence explained 47% of the trait-PF variance; % change in R-R explained 43% of the state-PF variance. Models based on resting R-R and TUG-DT explained 39% of the state-PF.

DISCUSSION

These findings demonstrate that specific gait measures better capture trait-PF, while ANS metrics better capture state-PF. To capture both physical fatigue aspects, the first 3 min of the 6MWT are sufficient. Alternatively, TUG-DT and ANS rest metrics can be used for state-PF prediction in pwMS when the 6MWT is not feasible.

Workload Assessment in Remote Mixed Reality Medical Procedural Training Through Physiological Signals

Mixed reality (MR) technology has been adopted for teaching and procedural planning/guidance in medicine, but its impact on performance is not well understood. Evaluation of cognitive load during MR-augmented learning experiences could help to quantify its utility. In this study, we performed a cognitive load analysis using physiological signals, specifically pupillary diameter (PD) and heart rate variability (HRV), to assess the learning experience of students performing simulated ultrasound-guided central venous catheterization (CVC) through MR remote assistance. We evaluated the cognitive load in students performing high-precision (vessel location and needle insertion) and low-precision (guidewire and catheter insertion) portions of the US CVC procedure and compared them to the results of students learning via teleconferencing software. The mean PD after baseline correction was lower, an indicator of decreased cognitive load, during high-precision MR-guided tasks than during the lower-precision tasks (3.80 vs 7.42 px, p<0.09). The observed changes in PD suggest a positive impact on the overall teaching experience for students exposed to holographic objects during training. Heart rate variability, measured by a ratio of low to high-frequency power, showed a similar but non-significant trend. No significant differences were seen in high vs low precision task workload in the control group. Our findings provide valuable insights into the potential benefits of incorporating holographic objects into complex medical procedure training.Clinical relevance- The study demonstrates that within MR, the cognitive load during medical procedural training is reduced when providing augmented 3D models in MR that are utilized by the instructor.

Heart Rate Variability Thresholds: Agreement with Established Approaches and Reproducibility in Trained Females and Males

PURPOSE

To determine in trained females and males i) the agreement between the gas exchange threshold (GET), lactate threshold 1 (LT1), and heart rate variability threshold 1 (HRVT1), as well as between the respiratory compensation point (RCP), lactate threshold 2 (LT2), and heart rate variability threshold 2 (HRVT2), and ii) the reproducibility of HRVT1 and HRVT2 during 2-min incremental step protocols.

METHODS

Fifty-seven trained participants (24 females) completed a 2-min step incremental test to task failure. Nineteen participants (eight females) completed a second test to evaluate reproducibility. Gas exchange and ventilatory responses, blood lactate concentration, and RR time series were recorded to assess the oxygen consumption (V̇O 2 ) and heart rate (HR) associated with the GET, RCP, LT1, LT2, HRVT1, and HRVT2.

RESULTS

V̇O 2 -GET versus V̇O 2 -HRVT1 and HR-GET versus HR-HRVT1 were statistically different for females (29.5 ± 4.0 vs 34.6 ± 6.1 mL·kg -1 ·min -1 ; 154 ± 11 vs 166 ± 12 bpm) and for males (33.9 ± 4.2 vs 42.7 ± 4.6 mL·kg -1 ·min -1 ; 145 ± 11 vs 165 ± 9 bpm; P < 0.001). V̇O 2 and HR at HRVT1 were greater than at LT1 ( P < 0.05). V̇O 2 -RCP versus V̇O 2 -HRVT2 and HR-RCP versus HR-HRVT2 were not statistically different for females (40.1 ± 4.7 vs 39.5 ± 6.7 mL·kg -1 ·min -1 ; 177 ± 9 vs 176 ± 9 bpm) and males (48.4 ± 5.4 vs 47.8 ± 4.8 mL·kg -1 ·min -1 ; 176 ± 8 vs 175 ± 9 bpm; P > 0.05). V̇O 2 and HR responses at LT2 were similar to HRVT2 ( P > 0.05). Intraclass correlation coefficient for V̇O 2 -HRVT1, HR-HRVT1, V̇O 2 -HRVT2, and HR-HRVT2 indicated good reproducibility when comparing the two different time points to standard methods.

CONCLUSIONS

Whereas HRVT2 is a valid and reproducible estimate of the RCP/LT2, current approaches for HRVT1 estimation did not show good agreement with outcomes at GET and LT1.

Differences in Cardiorespiratory Responses with Three Set-Paced Submaximal Endurance Tests in Community-Dwelling Older Adults

A variety of submaximal exercise tests are commonly used in clinical practice to determine an individual's exercise capacity and cardiorespiratory fitness. This study explored differences in cardiorespiratory and perceived exertion responses following the completion of three set-paced exercise tests. A prospective, observational, cross-sectional design assessed 30 healthy communityd-welling older adults, who participated in three submaximal exercise tests, including seated marching (SM), standing marching (STM), and standing stepping (STS). Each test was three minutes in length and required the participant to step at a set pace. Heart rate (HR), blood pressure (BP), rate of perceived exertion (RPE), and submaximal oxygen uptake (VO2) were measured before and after each test. Repeated measures ANOVA with Bonferroni correction tested for differences. Statistically significant differences between pre and post exercise values were noted for HR, SBP, RPE and VO2 (p < 0.01) between the three activities. Additionally, 3-minutes of standing stepping triggered the highest cardiorespiratory responses with a mean metabolic equivalent (MET) of 6.18 compared to seated stepping that triggered the lowest responses with a mean MET value of 1.98. The results of this study provide meaningful data on significant differences noted in cardiorespiratory and perceived exertion elicited following the completion of three set-paced stepping exercises. Based on the results, STM and STS can be categorized as moderate intensity activities, while three minutes of set paced SM is light intensity activity. Further research is warranted to validate these findings in older adults with multiple comorbidities and in those consuming cardiac medications that alter hemodynamic responses.

Moderate cardiac vagal tone is associated with more cooperation in children

Childhood is a crucial period for prosocial development, including cooperative behaviors. Recent studies have shown a quadratic relation (inverted U-shape curve) between cardiac vagal tone (CVT) and various prosocial emotions and behaviors in children, but data are lacking on cooperative behaviors. In a sample of 111 school-aged children (M = 7.77; SD = 1.24, range: 6-11), we tested the association between the root mean square of successive differences in interbeat intervals (RMSSD) at rest, and cooperative behavior in a task designed to be comparable to a stag hunt game. We found evidence for an association between RMSSD and cooperation that follows an inverted U-shape. In addition, older children were more likely to cooperate than younger children. Lastly, we found an interaction between RMSSD and age such that the association between RMSSD and cooperation behavior was present for younger but not older children. In addition, we proposed an extension of the Johnson-Neyman test to assess the significant region of interaction between age and the linear and quadratic RMSSD. These results add to a growing literature suggesting that moderate RMSSD is associated with greater prosocial behavior and provide novel evidence that this association extends to children's cooperation.