Amy Clark

High-intensity Interval Training Increases Cardiac Output and V˙o2max

Increases in maximal oxygen uptake (V˙O2max) frequently occur with high-intensity interval training (HIIT), yet the specific adaptation explaining this result remains elusive. Purpose This study examined changes in V˙O2max and cardiac output (CO) in response to periodized HIIT. Methods Thirty-nine active men and women (mean age and V˙O2max = 22.9 ± 5.4 yr and 39.6 ± 5.6 mL·kg−1·min−1) performed HIIT and 32 men and women (age and V˙O2max = 25.7 ± 4.5 yr and 40.7 ± 5.2 mL·kg−1·min−1) were nonexercising controls (CON). The first 10 sessions of HIIT required eight to ten 60 s bouts of cycling at 90%–110% percent peak power output interspersed with 75 s recovery, followed by randomization to one of three regimes (sprint interval training (SIT), high-volume interval training (HIITHI), or periodized interval training (PER) for the subsequent 10 sessions. Before, midway, and at the end of training, progressive cycling to exhaustion was completed during which V˙O2max and maximal CO were estimated. Results Compared with CON, significant (P < 0.001) increases in V˙O2max in HIIT + SIT (39.8 ± 7.3 mL·kg−1·min−1 to 43.6 ± 6.1 mL·kg−1·min−1), HIIT + HIITHI (41.1 ± 4.9 mL·kg−1·min−1 to 44.6 ± 7.0 mL·kg−1·min−1), and HIIT + PER (39.5 ± 5.6 mL·kg−1·min−1 to 44.1 ± 5.4 mL·kg−1·min−1) occurred which were mediated by significant increases in maximal CO (20.0 ± 3.1 L·min−1 to 21.7 ± 3.2 L·min−1, P = 0.04). Maximal stroke volume was increased with HIIT (P = 0.04), although there was no change in maximal HR (P = 0.88) or arteriovenous O2 difference (P = 0.36). These CO data are accurate and represent the mean changes from pre- to post-HIIT across all three training groups. Conclusions Increases in V˙O2max exhibited in response to different HIIT regimes are due to improvements in oxygen delivery.

The Polar® OH1 Optical Heart Rate Sensor is Valid during Moderate-Vigorous Exercise

Purpose Traditional heart-rate monitoring through the use of electrocardiograms or chest-worn heart rate sensors can be challenging in certain sports or in field settings. New technologies, such as photoplethysmography (PPG), have enabled heart-rate monitoring at alternate sites. However, to date, the accuracy and validity of various PPG sensors has not been examined in detail. The purpose of the present investigation was to determine the validity of an arm-worn PPG sensor during yoga sequences. Methods Fifteen college-aged men and women participated in a ~45 min power vinyasa yoga class. During the class, participants wore Polar ® H7 chest straps and RCX3 receivers (criterion) and Polar ® OH1 arm bands on their upper right arm (practical). Mean differences were compared via a paired t -test, heart rate during yoga using a time*device repeated measures ANOVA, and agreement assessed with Bland-Altman analysis. Results Mean heart rates during yoga were not different (mean difference=0.76, 95% CI: –0.54 to 2.06; p =0.229). Yoga created a main effect of time on heart rate ( p <0.0001), but there was no difference between devices ( p =0.86) or interaction ( p =0.90). Mean bias±95% limits of agreement was 0.76±1.30 bpm, with a typical error of 2.42±1.49 bpm and a coefficient of variation of 1.8±1.5%. Conclusions Results of the present investigation revealed that the Polar ® OH1 is a valid measure of heart rate during moderate-vigorous exercise. Future validation studies should consider other exercise modes and participant characteristics.

Heart rate and thermal responses to power yoga

BACKGROUND and Purpose: Yoga has grown in popularity and may offer a viable alternative form of physical activity. The purpose of this study was to examine heart rate, hydration, and thermal responses to a power yoga sequence. MATERIALS AND METHODS Twenty-seven men and women (n = 4/23; Mean ± SD age = 23.3 ± 3.3 years; BMI = 23 ± 3 kg m-2) underwent ∼45 min of power yoga. Heart rate and skin temperature were recorded. Mass was measured before and after exercise to estimate fluid loss. Time spent in light, moderate, and vigorous heart rate zones was calculated. RESULTS Heart rate and skin temperature increased (p < 0.0001). Participants spent more time in moderate and vigorous heart rate zones than in light intensity (p < 0.0001). There was a reduction in body mass (-0.28 ± 0.13 kg, p < 0.0001). CONCLUSION Power yoga may be considered moderate-vigorous intensity exercise, based on heart-rate.