Maximal heart rate (HR_max) is a fundamental measure used in exercise prescription. The Apple Watch™ measures heart rate yet the validity and inter-device variability of the device for measuring HR_max are unknown. Fifteen participants completed a maximal oxygen uptake test while wearing an Apple Watch™ on each wrist. Criterion HR_max was measured using a Polar T31™ chest strap. There were good to very good correlations between the watches and criterion (left: r = 0.87 [90%CI: 0.67 to 0.95]; right: r = 0.98 [90%CI: 0.94 to 0.99]). Standardised mean bias for the left and right watches compared to the criterion were 0.14 (90%CI: −0.12 to 0.39; trivial) and 0.04 (90%CI: −0.07 to 0.15; trivial). Standardised typical error of the estimate for the left and right watches compared to the criterion were 0.51 (90%CI: 0.38 to 0.80; moderate) and 0.22 (90%CI: 0.16 to 0.34; small). Inter-device standardised typical error was 0.46 (90%CI: 0.36 to 0.68; moderate), ICC = 0.84 (90%CI: 0.65 to 0.93). The Apple Watch™ has good to very good criterion validity for measuring HR_max, with no substantial under- or over-estimation. There were moderate and small prediction errors for the left and right watches. Inter-device variability in HR_max is moderate.

Moderate fitness levels and habitual exercise have a protective effect for cardiovascular disease, stroke, type 2 diabetes, and all-cause mortality. The Apple Watch displays exercise completed at an intensity of a brisk walk or above using a green "exercise" ring. However, it is unknown if the exercise ring accurately represents an exercise intensity comparable to that defined as moderate-intensity. In order for health professionals to prescribe exercise intensity with confidence, consumer wearable devices need to be accurate and precise if they are to be used as part of a personalized medicine approach to disease management. The aim of this study was to examine the validity and reliability of the Apple Watch for measuring moderate-intensity exercise, as defined as 40-59% oxygen consumption reserve (VO₂R). Twenty recreationally active participants completed resting oxygen consumption (VO₂rest) and maximal oxygen consumption (VO₂ max) tests prior to a series of 5-minute bouts of treadmill walking at increasing speed while wearing an Apple Watch on both wrists, and with oxygen consumption measured continuously. Five-minute exercise bouts were added until the Apple Watch advanced the green "exercise" ring by 5 minutes (defined as the treadmill inflection speed). Validity was examined using a one-sample t-test, with interdevice and intradevice reliability reported as the standardized typical error and intraclass correlation. The mean %VO₂R at the treadmill inflection speed was 30% (SD 7) for both Apple Watches. There was a large underestimation of moderate-intensity exercise (left hand: mean difference = -10% [95% CI -14 to -7], d=-1.4; right hand: mean difference = -10% [95% CI -13 to -7], d=-1.5) when compared to the criterion of 40% VO₂R. Standardized typical errors for %VO₂R at the treadmill inflection speed were small to moderate, with intraclass correlations higher within trials compared to between trials. The Apple Watch threshold for moderate-intensity exercise was lower than the criterion, which would lead to an overestimation of moderate-intensity exercise minutes completed throughout the day.

Background/Objectives: Advancements in breast cancer therapeutics, such as anthracyclines, are improving cancer survival rates but can have side effects that limit their use. Cardiotoxicity, defined as damage to the heart caused by cancer therapeutics, is characterised by a significant reduction in left ventricular ejection fraction (LVEF) and symptoms of cardiac dysfunction. Multiple oral supplements exist with antioxidant and anti-inflammatory properties that have the potential to lower cardiotoxicity risk and ameliorate the complications associated with left ventricular dysfunction. In this review, we evaluate the current status of using nutritional interventions to modulate cardiotoxicity. Methods: We used specific keywords to search for articles that met our predetermined inclusion and exclusion criteria to review the evidence and provide insights for future research. Results: Seven studies were identified as eligible for this review: six focused on oral supplementation strategies in breast cancer patients undergoing chemotherapy, and one focused on nutritional counselling and adherence to the Mediterranean diet in breast cancer survivors’ post-treatment. There was a significantly attenuated reduction in LVEF in five studies that monitored cardiometabolic health, and there were significant improvements in blood serum levels of cardiac biomarkers across all studies. Conclusions: Current evidence suggests that appropriate nutritional interventions, alongside chemotherapy, can modulate the risk of cardiotoxic side effects. This highlights the potential of oral antioxidant supplementation and Mediterranean diet counselling to decrease tertiary cancer therapy costs associated with cardiovascular complications.

The aims of this study were to estimate the walking cadence required to elicit a VO₂reserve (VO₂R) of 40% and determine if fitness status moderates the relationship between walking cadence and %VO₂R. Twenty participants (10 male, mean(s) age 32(10) years; VO₂max 45(10) mL·kg⁻¹·min⁻¹) completed resting and maximal oxygen consumption tests prior to 7 x 5-min bouts of treadmill walking at increasing speed while wearing an Apple Watch and measuring oxygen consumption continuously. The 7 x 5-min exercise bouts were performed at speeds between 3 and 6 km·h⁻¹ with 5-min seated rest following each bout. Walking cadence measured at each treadmill speed was recorded using the Apple Watch “Activity” app. Using Bayesian regression, we predict that participants need a walking cadence of 138 to 140 steps·min⁻¹ to achieve a VO₂R of 40%. However, these values are moderated by fitness status such that those with lower fitness can achieve 40% VO₂R at a slower walking cadence. The results suggest that those with moderate fitness need to walk at ~40% higher than the currently recommended walking cadence (100 steps·min⁻¹) to elicit moderate-intensity physical activity. However, walking cadence required to achieve moderate-intensity physical activity is moderated by fitness status.

Practitioners place importance on high-speed running (HSR) to monitor training practice and match-play demands, whilst attempting to maximise fitness and minimize the risk of injury occurrence. Practitioners apply various methods to quantify HSR, such as absolute thresholds, percentage of maximum sprint speed and maximal aerobic speed (MAS). A recent survey demonstrates the 5-minute run and 1200m shuttle test (ST) to be implemented among rugby league practitioners to quantify HSR by incorporating MAS. However, it is unclear as to how valid these methods are to accurately quantify MAS. Therefore, the aim of this study was to assess the validity of the 5-minute run and 1200m ST when compared to a gold standard measure for MAS. Twenty 1^st team professional rugby league players competing in the European Super League participated in this study. Players were required to complete an incremental treadmill test, 5-minute run and 1200m ST over a two-week period in pre-season. MAS, peak heart rate (HR_max), peak lactate (La_peak) and rating of perceived exertion (RPE) where collected upon completion of each test. Results demonstrated the 1200m ST to have a higher correlation for MAS than the 5-minute run (1200m ST: r = 0.73, 5-minute run: r = 0.64). However, when assessing validity using the level of agreement between data, the 5-minute run underreported MAS by 0.45 m·s^-1 whereas the 1200m ST underreported MAS by 0.77 m·s^-1. Ultimately, both field-based tests used in this study underreport MAS when compared to an incremental treadmill test, although the 5-minute run provides a closer agreement and therefore a more valid measurement for MAS than the 1200m ST.

As most sport drinks contain some form of non-nutritive sweetener (e.g. aspartame), and with the variation in blood glucose regulation and insulin secretion reportedly associated with aspartame, a further understanding of the effects on insulin and blood glucose regulation during exercise is warranted. Therefore, the aim of this preliminary study was to profile the insulin and blood glucose responses in healthy individuals after aspartame and carbohydrate ingestion during rest and exercise.