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.

The Influence of Tissue Plasminogen Activator I/D Polymorphism on the tPA Response to Exercise.

The purpose was to determine if the Alu-insertion (I)/deletion (D) polymorphism of the tissue plasminogen activator (tPA) gene influences the tPA response to maximal exercise. Fifty male subjects (age = 23.6 ± 4.7 yrs) completed a maximal treadmill exercise test. Blood samples were drawn before and immediately after exercise for determination of plasma tPA antigen and activity. Isolated DNA was amplified via polymerase chain reaction, electrophoresed, and visually amplified to determine tPA genotype. Subjects were classified as possessing the D allele (D) (n = 28) or being homozygous for the I allele (I) (n = 22). Differences in tPA antigen and activity were assessed using a two-factor (genotype and time) repeated measures analysis of variance. There were significant main effects for time for tPA antigen and activity (p < 0.05), but no main effect for genotype. Furthermore, there was no genotype x time interaction due to a similar increase in tPA antigen in the D group (pre-exercise = 5.83 + 2.39 ng/ml, post-exercise = 21.88 + 7.38 ng/ml) and the I group (pre-exercise = 5.61 + 2.82 ng/ml, post-exercise = 19.05 + 7.67 ng/ml) and a similar increase in tPA activity in the D group (pre-exercise = 0.39 ± 0.19 IU/ml, post-exercise = 9.73 ± 4.22 IU/ml) and I group (pre-exercise = 0.45 ± 0.29 IU/ml, post-exercise = 9.76 ± 5.50 IU/ml). The I/D polymorphism of the tPA gene does not influence the tPA antigen nor tPA activity responses to maximal exercise in healthy, young, sedentary males.

Age and aerobic training status effects on plasma and skeletal muscle tPA and PAI-1.

INTRODUCTION: Reductions in fibrinolytic potential occur with both aging and physical inactivity and are associated with an increased cardiovascular disease risk. Plasmin, the enzyme responsible for the enzymatic degradation of fibrin clots, is activated by tissue plasminogen activator (tPA), while plasminogen activator inhibitor-1 (PAI-1) inhibits its activation. Currently, fibrinolysis research focuses almost exclusively on changes within the plasma. However, tPA and PAI-1 are expressed by human skeletal muscle (SM). Currently, no studies have focused on changes in SM fibrinolytic activity with regard to aging and aerobic fitness. PURPOSE: The purpose of this study was to cross-sectionally evaluate effects of age and aerobic fitness on tPA and PAI-1 expressions and activity in SM. METHODS: Twenty-six male subjects were categorized into the following groups: (1) young aerobically trained (n = 8); (2) older aerobically trained (n = 6); (3) young aerobically untrained (n = 7); and (4) older aerobically untrained (n = 5). Muscle biopsies were obtained from each subject. SM tPA activity was assessed using gel zymography and SM tPA and PAI-1 expressions were assessed using RT-PCR. RESULTS: Trained subjects had higher SM tPA activity compared to untrained (25.3 ± 2.4 × 10(3) vs. 21.5 ± 5.6 × 10(3) pixels, respectively; p = 0.03) with no effect observed for age. VO2 max and SM tPA activity were also significantly correlated (r = 0.42; p < 0.04). SM tPA expression was higher in older participants, but no effect of fitness level was observed. No differences were observed for PAI-1 expression in SM. CONCLUSIONS: Higher levels of aerobic fitness are associated with increased fibrinolytic activity in SM.

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.

Discordant hemodynamic and fibrinolytic adaptations following a 6-week cardiac rehabilitation program.

The present study evaluated changes in hemodynamics and fibrinolysis during 6 weeks of participation in an exercise-based cardiac rehabilitation program. Fourteen patients trained for 3 days per week for 6 weeks using American College of Sports Medicine guidelines for intensity and duration. Blood samples were taken at baseline and after 3 and 6 weeks of participation and analyzed for tissue plasminogen activator (t-PA) activity and antigen, plasminogen activator inhibitor-1 (PAI-1) activity and antigen, and relative quantification of t-PA and PAI-1 RNA. Data were analyzed using repeated measures analysis of variance. Training elicited significant decreases in submaximal exercise heart rate and systolic blood pressure and resting systolic blood pressure (p<.05). There were no significant changes in plasma concentrations of t-PA or PAI-1, and no change was observed in t-PA or PAI-1 gene expression. The present findings suggest that favorable hemodynamic adaptations may occur after only 6 weeks of exercise-based cardiac rehabilitation, but longer training periods may be needed to elicit positive hemostatic adaptations.

Temporal changes in tPA and PAI-1 after maximal exercise.

PURPOSE: Although fibrinolysis increases with acute exercise, it decreases rapidly during the postexercise period. Therefore, the time point at which blood samples are collected postexercise could affect reported tissue plasminogen activator (t-PA) and/or plasminogen activator inhibitor-1 (PAI-1) levels. The purpose of this study was to determine the time course of t-PA and PAI-1 changes after acute maximal exercise. METHODS: Eight healthy males performed a graded maximal exercise test on a treadmill. Venous blood samples were collected using an indwelling catheter before exercise and at 1, 2, 4, 6, 8, and 10 min postexercise. Mean differences in t-PA activity, t-PA antigen, and PAI-1 activity at each time point were assessed using a repeated measures ANOVA. Post hoc means comparisons were performed by contrasting the 1-min postexercise value against all other time points. RESULTS: Both t-PA activity and t-PA antigen significantly increased from pre- to postexercise (P < 0.05). t-PA activity did not change from 1 to 2 min postexercise but decreased significantly at 4 min postexercise. Likewise, t-PA antigen remained elevated from 1 to 2 min postexercise but decreased at 4 min postexercise. PAI-1 decreased from pre- to postexercise but did not change during the 10-min postexercise period. CONCLUSION: To accurately evaluate the t-PA response to acute exercise, blood samples should be collected within 2 min after the cessation of exercise.

Coagulation and fibrinolytic responses to manual versus automated snow removal.

PURPOSE: The purpose of this study was to assess coagulation and fibrinolytic responses to snow removal. METHODS: Thirteen healthy male subjects (age = 26 +/- 5 yr, height = 179.0 +/- 7.0 cm, weight = 78.7 +/- 16.1 kg, .VO2max = 54.7 +/- 8.9 mL.kg-1.min-1) underwent maximal treadmill stress testing (TM), 10 min of snow shoveling (SS), and 10 min of snow removal using an automated snow thrower (ST). Blood was collected immediately before and after each test and analyzed for von Willebrand Factor antigen (vWF:ag), tissue plasminogen activator (tPA) antigen, and plasminogen activator inhibitor-1 (PAI-1) activity. Data were analyzed using a two-factor repeated-measures analysis of variance. RESULTS: vWF:ag significantly increased during TM (84.7 +/- 21.7% normal preexercise, 149.0 +/- 45.6% normal postexercise) but not SS or ST. TM resulted in significant increases in tPA antigen (6.54 +/- 2.76 ng.mL-1 preexercise, 21.39 +/- 10.56 ng.mL-1 postexercise) and both SS and TM caused significant reductions in PAI-1 activity (SS = 15.1 +/- 3.8 AU.mL-1 preexercise, 13.2 +/- 4.3 AU.mL-1 postexercise; TM = 15.3 +/- 3.6 AU.mL-1 preexercise, 10.5 +/- 5.3 AU.mL-1 postexercise). Postexercise PAI-1 activity was significantly lower for TM versus SS. tPA antigen was unchanged after SS and ST, and PAI-1 activity was unchanged after ST. CONCLUSION: vWF:ag is unchanged after self-paced snow shoveling and automated snow removal in young, healthy males. Snow shoveling acutely increases fibrinolytic potential in this population, although not to the degree observed after maximal treadmill exercise.

Exercise-induced changes in coagulation and fibrinolysis in healthy populations and patients with cardiovascular disease.

This review highlights the clinical significance of coagulation and fibrinolytic responses, and adaptations in healthy individuals and patients with cardiovascular disease (CVD). Much of the review focuses on indicators of the potential for coagulation and fibrinolysis. The terms 'coagulation potential' and 'fibrinolytic potential' are used frequently, as much of the literature in the area of exercise haemostasis evaluates factors that reflect an increased potential for coagulation, while coagulation per se, may or may not be occurring. Similarly, fibrinolysis is definitively the lysis of inappropriate or excessive blood clot, which may or may not be occurring when the enzymes that stimulate fibrinolysis are activated. Nevertheless, markers of coagulation and fibrinolytic potential are associated with CVD, ischaemic events, and cardiovascular mortality. Additionally, fibrinolytic potential is associated with other established CVD risk factors. Ischaemic events triggered by physical exertion are more likely to occur due to an occlusive thrombus, suggesting the exercise-induced responses related to haemostasis are of clinical significance. The magnitude of increase in coagulation potential, platelet aggregation and fibrinolysis appears to be primarily determined by exercise intensity. Patients with CVD may also have a larger increase in coagulation potential during acute exercise than healthy individuals. Additionally, the magnitude of the fibrinolytic response is largely related to the resting fibrinolytic profile of the individual. In particular, high resting plasminogen activator inhibitor-1 may diminish the magnitude of tissue plasminogen activator response during acute exercise. Therefore, acute responses to exercise may increase the risk of ischaemic event. However, chronic aerobic exercise training may decrease coagulation potential and increase fibrinolytic potential in both healthy individuals and CVD patients. Due to the aforementioned importance of resting fibrinolysis on the fibrinolytic response to exercise, chronic aerobic exercise training may cause favourable adaptations that could contribute to decreased risk for ischaemic event, both at rest and during physical exertion.