Examining the Accuracy of the Polar A360 Monitor.

ABSTRACT: Rider, BC, Conger, SA, Ditzenberger, GL, Besteman, SS, Bouret, CM, and Coughlin, AM. Examining the accuracy of the Polar A360 monitor. J Strength Cond Res 35(8): 2165-2169, 2021-The purpose of this study was to determine the accuracy of the Polar A360 heart rate (HR) monitor during periods of rest, walking/running, and active/passive recovery from exercise. Thirty collegiate athletes (women n = 15 and men n = 15) wore an A360 monitor and a previously validated chest HR monitor (Polar RS400) that served as the criterion measurement across a range of resting and walking/running intensities. First, subjects rested in a supine, seated, and standing position. Next, each subject walked on a treadmill at 1.6 kilometers per hour (kph). Speed was increased by 1.6 kph every 2 minutes until volitional fatigue. Then, subjects walked at 4.8 kph followed by a seated recovery stage. Heart rate was recorded in 30-second increments. Total mean difference in HR readings, percent accuracy, and intraclass correlation coefficient (ICC) analysis established the level of agreement between devices. Bland-Altman plots and a regression were used to examine the agreement between devices. The A360 demonstrated a strong correlation with the RS400 (r2 = 0.98) across time points. The analysis of variance with repeated measures indicated an overall significant difference (p < 0.001) between devices. The A360 significantly underestimated HR during the 6.4-kph speed only (p < 0.05) (effect size 0.26). The greatest percent accuracy occurred during rest (91%) and recovery (90%). An ICC of 0.98 (SEM: 0.35) demonstrates a strong level of agreement between devices. The A360 is accurate at rest and during various walking and running speeds and thus is a device that can be used with confidence by athletes for specific training purposes. Future research should examine accuracy during weight training and other sport-specific activities.

Psycho-Physiological Effects of Television Viewing During Exercise.

We propose that enjoyment is an important factor in the adoption and long-term maintenance of exercise. Television (TV) viewing is believed to be a highly enjoyed leisure-time activity, combining it with exercise may make for a more enjoyable exercise experience. The objective of this study was to examine the effects of television (TV) viewing on psychological and physiological variables during a moderate-intensity exercise bout. Twenty-eight insufficiently active (<150 minutes per week of moderate intensity PA and/or 75 minutes of vigorous PA) adults (Age: M = 47.4 ± 7.6 years) participated in this study. Each participant performed three separate 30-minute walking bouts on a motorized treadmill. During each bout, participants watched a program they selected (30-minute scripted show) (self-selected TV condition), a British Broadcasting Corporation (BBC) nature program (standardized TV condition), or no TV program (no TV condition). Participants were unable to select the nature program as their self-selected program, as it was not a 30-minute scripted program. A Polar Heart Rate (HR) monitor and validated surveys on affect and enjoyment were used. Participants reported greater enjoyment of exercise for both self-selected and standardized TV conditions (97.1 ± 15.2 and 92.7 ± 15.2), compared to the No TV condition (77.5 ± 13.4, p < 0.001). The two TV conditions resulted in similar levels of focus on TV viewing (self-selected TV: 81.2 ± 19.7; standardized TV: 79.1 ± 14.2, p > 0.05) and dissociation from walking (self-selected TV: 38.1 ± 6.7 and standardized TV: 33.2 ± 3.9); they also resulted in more dissociation than the no TV condition (TV: 72.6 ± 5.6, p = 0.002). The findings indicate that TV viewing, regardless of whether the programming is self-selected or standardized, associates with greater enjoyment of exercise.

Characterization of the effects of the vasopressin V2 receptor on sweating, fluid balance, and performance during exercise.

A regulatory effect of arginine vasopressin (AVP) on sweat water conservation has been hypothesized but not definitively evaluated. AVP-mediated insertion of sweat and salivary gland aquaporin-5 (AQP5) water channels through activation of the vasopressin type 2 receptor (V2R) remains an attractive, yet unexplored, mechanism that could result in a more concentrated sweat with resultant decreased water loss. Ten runners participated in a double-blind randomized control treadmill trial under three separate pharmacological conditions: a placebo, V2R agonist (0.2 mg desmopressin), or V2R antagonist (30 mg tolvaptan). After a familiarization trial, runners ran for 60 min at 60% of peak speed followed by a performance trial to volitional exhaustion. Outcome variables were collected at three exercise time points: baseline, after the steady-state run, and after the performance run. Body weight losses were <2% across all three trials. Significant pharmacological condition effects were noted for urine osmolality [F = 84.98; P < 0.0001] and urine sodium concentration ([Na(+)]) [F = 38.9; P < 0.0001], which verified both pharmacological activation and inhibition of the V2R at the kidney collecting duct. Plasma osmolality and [Na(+)] demonstrated significant exercise (F = 26.0 and F = 11.1; P < 0.0001) and condition (F = 5.1 and F = 3.8; P < 0.05) effects (osmolality and [Na(+)], respectively). No significant exercise or condition effects were noted for either sweat or salivary [Na(+)]. Significant exercise effects were noted for plasma [AVP] (F = 22.3; P < 0.0001), peak core temperature (F = 103.3; P < 0.0001), percent body weight change (F = 6.3; P = 0.02), plasma volume change (F = 21.8; P < 0.0001), and thirst rating (F = 78.2; P < 0.0001). Performance time was not altered between conditions (P = 0.80). In summary, AVP acting at V2R does not appear to regulate water losses from body fluids other than renal excretion during exercise.

Effect of compression stockings on physiological responses and running performance in division III collegiate cross-country runners during a maximal treadmill test.

There is a growing trend for runners to use compression stockings (CS) to improve performance. The purpose of this study was to determine the effect of CS on physiological variables associated with running performance. Participants were 10 NCAA division III cross-country runners. The study used a randomized, crossover design with 2 conditions (with CS and without CS). Both conditions consisted of a maximal treadmill test that involved 3-minute stages of increasing speed and incline, separated by a minute and one-half walking recovery stage. Seven days later, the participants repeated the maximal test but switched CS condition. Heart rate, blood lactate (BLa), blood lactate threshold, maximal oxygen consumption (VO2max), respiratory exchange ratio, rating of perceived exertion, and time to fatigue were measured. Before and during the maximal treadmill tests, the variables showed no significant difference (p ≤ 0.05) between the CS conditions. Blood lactate was lower while wearing CS when measured during recovery at the 1-minute (CS = 13.3 ± 2.9 mmol · L(-1), non-CS = 14.8 ± 2.8 mmol · L(-1), p = 0.03) and the 5-minute (CS = 11.0 ± 2.7 mmol · L(-1), non-CS = 12.8 ± 2.8 mmol · L(-1), p = 0.02) periods. Time to fatigue was longer without CS (CS = 23.570 ± 2.39 minutes, non-CS = 23.93 ± 2.49 minutes, p = 0.04). These findings suggest that CS may not improve running performance, but could lend credence to certain manufacturers' claims of improved recovery through lower BLa values after exercise.

Monitoring capabilities of the Omron HJ-720ITC pedometer.

PURPOSE: The purpose of our study was to examine the monitoring capabilities of the Omron HJ-720ITC pedometer and determine the feasibility of using it in physical activity interventions. METHODS: Using data from an 8-week lifestyle-intervention study, we tested the capabilities of the pedometer for recording physical activity data. Data from a total of 28 subjects were used in our analysis. The total number of patient steps per day was recorded over the duration of an intervention, as well as "aerobic steps per day" (ie, those taken at a cadence of > 60 steps per minute for ≥ 10 consecutive minutes). Daily wear time was computed in order to ascertain participant compliance in wearing the pedometer. In addition, aerobic steps per minute were computed, providing an assessment of activity intensity during continuous walking bouts. RESULTS: Total steps per day and aerobic steps per day increased from baseline assessment to Week 8. Participants exceeded 100 steps/minute for 89% of their aerobic minutes, suggesting that they were in the moderate-intensity range (3-6 metabolic equivalent tasks) when performing continuous bouts of walking (> 10 minutes). CONCLUSION: The new pedometer is a reasonably priced, wearable activity monitor that is feasible for use in clinical and research settings.

The Effect of Compression Socks on Maximal Exercise Performance and Recovery in Insufficiently Active Adults.

In athletic populations, compression socks (CS) may improve exercise performance recovery. However, their potential to improve performance and/or recovery following exercise in non-athletic populations is unknown. Our study evaluated the effects of CS on exercise performance and recovery from a graded maximal treadmill test. Insufficiently active adults (n = 10, 60% female, average physical activity ~60 minutes/week) performed two graded maximal exercise tests; one while wearing below-knee CS, and the other trial with regular socks (CON). Order of trials was randomized. For both trials, heart rate, lactate, and rating of perceived exertion were measured at each stage and at one, five, and ten-minutes post-exercise. Additionally, recovery variables (soreness, tightness, annoyingness, tenderness, pulling) were measured at 24 and 48 hours post-exercise using a visual analog scale. Paired-samples t-tests were used to compare exercise and recovery variables between CS and CON trials. Heart rate, lactate, and rating of perceived exertion were not different between trials for any stage during the exercise test or immediate recovery. Most 24-and 48-hour recovery variables were significantly improved after the CS trial, with values 34.6 - 42.3% lower at 24 hours and 40.3 - 61.4% lower at 48 hours compared to CON. Compression socks provided a significant and meaningful improvement in recovery variables 24-48 hours following maximal exercise. Therefore, CS may remove a common barrier to exercise adherence and facilitate more effective training recovery for insufficiently active adults.

Ischemic Preconditioning Does Not Improve Time Trial Performance in Recreational Runners.

Some evidence indicates that ischemic preconditioning (IPC) may positively affect endurance exercise performance, but IPC's effect on running performance is unclear. This study's purpose was to examine the effect of IPC on running performance in recreational runners. Participants (n=12) completed IPC, a sham (SH) condition, and a leg elevation without blood restriction (LE) control condition on separate days (order randomized). For IPC, blood was restricted using blood pressure cuffs inflated to 220 mmHg at the thigh. For SH, the cuffs were inflated to only 20 mmHg. For LE, participants positioned their legs at 90 degrees against a wall while laying supine. The duration of each protocol was 30 minutes (three 5-minute bouts with 5-minute breaks). Following each protocol, participants ran 2.4 kilometers as fast as possible on a motorized treadmill. Run time, heart rate, and perceived exertion were measured and statistically compared, using repeated-measures ANOVA, each 0.8 kilometers. There were no differences in heart rate or time trial performance across protocols (p>0.05; IPC, 612.5±61.2 sec; SH, 608.1±57.9 sec; LE, 612.7±59.1 sec). Rating of perceived exertion at 0.8 kilometers was significantly lower for the IPC protocol than SH in females only (~5.7%, or ~0.8 points on a 6-20 scale; p<0.05). Our IPC protocol did not improve running performance or physiological parameters during a time trial run in recreational runners. The performance benefit seen in this study's most fit individuals suggests that fitness level may influence IPC's efficacy for improving endurance running performance.

Portable open-circuit spirometry systems.

BACKGROUND: The purpose of this review is to describe the evolution of portable open-circuit spirometry systems, and discuss their validity, reliability, and principles of operation. METHODS: Eleven devices were selected for review: the Oxylog, Aerosport KB1-C, Cosmed K2, Cosmed K4RQ, Cosmed K4b2, MetaMax I, MetaMax II, Metamax3B/VmaxST, Medgraphics VO2000, Oxycon Mobile I and Oxycon Mobile II. The validity (compared to the Douglas bag method [DBM]) and reliability of each device for measuring VO2 was summarized. RESULTS: Mean differences in resting measurements of VO2 were within ±0.05 L/min for all devices except one (difference of 0.17 L/min). When compared to the DBM, VO2 differences for all devices ranged from 0.01 L/min to 0.29 L/min during submaximal intensity exercise and from 0.01 L/min to 0.36 L/min during vigorous/maximal intensity. During submaximal and maximal intensities, ICC ranged from 0.66-0.99 and CV ranged from 2.0-14.2%. Of these devices, four used breath-by-breath technology and six used micro-proportional sampling technology. Validity and reliability of devices did not seem to differ between methods of gas collection. CONCLUSIONS: Of the three commercially available devices in 2015, all were found to be reliable. Two of the three systems (Cosmed K4b2 and Oxycon Mobile II) provided valid estimates of VO2 (mean values within ±0.10 L/min of DBM) during rest, and submaximal and maximal intensities, while the MetaMax3B slightly overestimated VO2, particularly at maximal exercise.

Detection of lying down, sitting, standing, and stepping using two activPAL monitors.

UNLABELLED: The activPAL is an accelerometer-based monitor worn on the thigh that classifies daily activities into three categories (sitting/lying down, standing, and stepping). The monitor discriminates between sitting/lying and the upright position by detecting the inclination of the thigh. It detects stepping from the acceleration versus time wave form. However, a current limitation of the activPAL is that it does not discriminate between sitting and lying down. PURPOSE: This study aimed to determine whether placing a second activPAL monitor on the torso would allow the detection of seated versus lying postures. METHODS: Fifteen healthy adults (18-55 yr of age) wore an activPAL on the right thigh and another activPAL over the right rib cage. Both monitors were synchronized and initialized to record data in 15-s epochs. Participants performed a semistructured routine of activities for 3 min each. Activities included lying down (while supine, prone, and on the side), sitting, standing, sweeping, treadmill walking at 3 mph, and treadmill running at 6 mph. The spatial orientation of the thigh and chest monitors was used to determine body posture, and the activPAL on the thigh was used to detect ambulation. RESULTS: The use of two activPAL devices enabled four behaviors to be accurately classified. The percentages of observations that were classified accurately were as follows: lying down (100%), sitting (100%), standing/light activity in the upright position (90.8%), and stepping (100%). CONCLUSIONS: The current method allows researchers to obtain more detailed information on postural allocation compared with that in the use of a single activPAL on the thigh.

Detecting indoor and outdoor environments using the ActiGraph GT3X+ light sensor in children.

INTRODUCTION: Experts recommend children spend more time playing outdoors. The ambient light sensor of the ActiGraph GT3X+ provides lux measurements. A lux is the International System's unit of illumination, equivalent to 1 lm·m. Few studies have established a lux threshold for determining whether a child is indoors or outdoors. PURPOSE: This study aimed 1) to assess the reliability of the ActiGraph GT3X+ ambient light sensor, 2) to identify a lux threshold to accurately discriminate between indoor and outdoor activities in children, and 3) to test the accuracy of the lux threshold in a free-living environment. METHODS: In part 1, a series of reliability tests were performed using 20 ActiGraph GT3X+ monitors under different environmental conditions. Cronbach's alpha was used to determine interinstrument reliability. In part 2, 18 children performed 11 different activities (five indoors and six outdoors) for 6 min each. The optimal threshold for detecting indoor/outdoor activity was determined using a receiver operator characteristic curve analysis. In part 3, 18 children at a preschool wore the monitor during a school day. Percent accuracy was determined for all conditions. RESULTS: In part 1, the devices had Cronbach's alpha values of 0.992 and 1.000 for indoor and outdoor conditions, respectively, indicating high interinstrument reliability. In part 2, the optimal lux threshold was determined to be 240 lux (sensitivity = 0.92, specificity = 0.88, area under the curve = 0.96, 95% CI = 0.951-0.970). In part 3, results of the school-day validation demonstrated the monitor was 97.0% accurate for overall detection of indoor and outdoor conditions (outdoor = 88.9%, indoor = 99.1%). CONCLUSIONS: The results demonstrate that an ActiGraph GT3X+ lux threshold of 240 can accurately assess indoor and outdoor conditions of preschool children in a free-living environment.