The Effectiveness of Running Power as a Metric of Exercise Intensity During Running Interval Training

Wearable power meters are increasingly popular among runners with Coros and Stryd offering running power as a real-time, trackable of a metric. PURPOSE: This study compared running power (RP) to physiological measures, heart rate (HR) and oxygen consumption (VO2), across high and low intensity running intervals. METHODS: Thirteen adult participants (n = 6 male; height = 174.9 ± 6.9 cm; mass = 72.5 ± 12.0 kg) were equipped with a Stryd 27 RP meter, a Polar H10 HR monitor, and a Cosmed K5 portable metabolic unit. Participants’ self-selected RP was obtained during a 10-min run on an indoor track (10 laps/mile). After resting for five minutes, participants ran another 10 min, alternating between equal intervals of RP 20% higher and 20% lower than self-selected RP: 120 s × 2, 60 s × 2, 30 s × 4, and 15 s × 8. All devices were started simultaneously before each run. RP (W/kg) was sampled at 1 Hz. HR (bpm) and VO2 (mL/kg/min) were sampled at 0.1 Hz throughout the interval run. Data were analyzed from the 60 s mark through the end of the run. HR and VO2 data were interpolated to 1 Hz, and cross correlations (max lag = 60 s) were used to compare RP, HR, and VO2 (mean values in Table 1). RESULTS: There were weak to moderate correlations between RP and VO2 (r = 0.351; lag = -29.1 s), RP and HR (r = 0.475; lag = 9.38 s), and HR and VO2 (r = 0.572; lag = -29.1 s; Table 2). CONCLUSION: HR showed the strongest correlation and smallest time delay with RP. This may be practically useful because HR data is more readily available to runners than VO2. However, the correlation is only moderate. While related, the three metrics of running intensity are fundamentally different. When exercising at a moderate intensity, changes in HR or VO2, which take seconds to minutes to stabilize, may be less evident than changes in mechanical power, which are immediate. Thus, it is possible that HR and VO2 would show a stronger relationship with RP across intervals longer than the 120 s maximum observed here. While RP can be a useful metric, it may not be informative about physiological responses to running especially over short intervals or when running at high intensity

Perceived Fatigue and Physical Activity Enjoyment Following Indoor and Outdoor Moderately Heavy Superset Resistance Training

ACSM has again determined that resistance training (RT) and outdoor activities are two of the top ten worldwide fitness trends for 2023. We previously found that RT outdoors had a significantly lower perception of effort (RPE) compared to indoor RT, despite no physiological differences in heart rate (HR) and energy expenditure (EE). However, no study has examined other feelings during RT in indoor or outdoor settings. PURPOSE: To determine how indoor or outdoor environments effect perceptions of fatigue and physical activity enjoyment following RT in recreationally resistance trained adults. METHODS: Twenty-three adult participants (n=10 female, n=13 male) completed this study. The Visual Analog Scale Fatigue (VAS-F) measured perceived fatigue and the Physical Activity Enjoyment Scale – Short Version (PACES-S) measured PA enjoyment, and both were measured at baseline and then immediately following an acute session of indoor or outdoor RT. HR was obtained from a chest strap (Polar H10) and EE from a Portable Metabolic Cart (COSMED K5). Randomly in indoor and outdoor settings, participants completed 4 supersets of the reverse lunge and shoulder press exercises using dumbbells at a light (2 sets) and moderately heavy (2 sets) intensity with 1 superset of 6 repetitions per exercise and 1 min rest between supersets. A paired T-test (for HR & EE comparisons) or one-way repeated measures ANOVA with Sidak post-hoc test (for VAS-F & PACES-S comparisons) were used to determine differences (p\u3c0.05). RESULTS: No significant differences were observed between indoor and outdoor RT for the physiological variables of average HR (129.4±17.2 and 127.75±23.3 bpm, respectively, p=0.66) and EE (30.6±11.5 and 28.3±9.9 kcals, respectively, p=0.06). Perceived fatigue significantly (p\u3c0.0001) increased from baseline (1.13±0.94 arbitrary units, AU’s) following indoor (4.54±1.91 AU’s) and outdoor (3.99±1.54 AU’s) RT, but no environmental differences (p=0.36) were observed. PA enjoyment was not significantly (p range: 0.27-0.93) different between baseline (18.73±1.83 AU’s) and following indoor (18.18±1.99 AU’s) or outdoor (18.36±1.99 AU’s) RT. CONCLUSION: In recreationally resistance trained adults, moderately heavy superset RT in indoor or outdoor settings does not alter perceived fatigue or physical activity enjoyment