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Thigh-worn accelerometry is commonly implemented to measure step cadence. The default activPAL CREA algorithm is a valid measure of cadence during walking, but its validity during running is unknown. The ActiPASS software is designed to analyse tri-axial accelerometry data from various brands. We tested the validity of CREA v1.3 and ActiPASS 2023.12 to measure step cadence against manually-counted steps. Forty-five participants (26♀, 23.4 ± 4.6 years) completed 5 walking (6 min each, 2–4 mph) and 5 running treadmill (5–7 mph) stages (423 total stages completed). Based on equivalence testing, walking cadence (stages 1–5: 92–124 steps/min) from CREA was statistically equivalent (zone: <±2.2% of the manually-counted mean) to manual counts (92–125 steps/min). However, CREA underpredicted cadence during running stages (stages 6–10: 143–135 steps/min) by ~ 11–20 steps/min (p < 0.001). The ActiPASS-derived cadences were equivalent (zone: <±3.3%) to manual counts for all walking stages (99–127 steps/min) except Stage 1 (zone: ±10.5%). ActiPASS underpredicted cadences during running (stages 6–10: 137–153 steps/min) by ~ 10–16 steps/min (p < 0.001) compared to manual counts (stages 6–10: 154–164 steps/min). The CREA v1.3 algorithm is a valid measure of cadence during walking while ActiPASS 2023.12 is a valid measure of cadence during medium-fast walking. Further research is required to improve step cadence estimation across ambulation speeds. [ABSTRACT FROM AUTHOR]

Heart rate variability (HRV) is a well-established noninvasive marker of autonomic cardiac control. We test whether time spent sitting (negatively) versus lying (positively) influences vagal HRV outcomes. HRV (10 min supine electrocardiogram) and free-living postures (dual-accelerometer configuration, 7 days) were measured in 31 young healthy adults (15♀, age: 23 ± 3 years). Habitual lying (66 ± 61 min/day), but not sitting time (558 ± 109 min/day), total sedentary time (623 ± 132 min/day), nor step counts (10 752 ± 3200 steps/day; all, p > 0.090), was associated with root mean square of successive cardiac interval differences (ρ = −0.409, p = 0.022) and normalized high-frequency HRV (ρ = −0.361, p = 0.046). These findings document a paradoxical negative impact of waking lying time on cardioautonomic function. Take home message Using a multi-accelerometer configuration, we demonstrated that more habitual waking time lying, but not sitting or total sedentary time, was associated with worse vagally mediated cardiac control. [ABSTRACT FROM AUTHOR]

Device-based measures often rely on the positive relationship between walking cadence and metabolic equivalents of task (METs) to estimate physical activity. It is unknown whether this relationship remains during jogging/running. The study purpose was to investigate the relationships between METs, cadence, and step length during walking and jogging/running. A treadmill protocol with 5 walking (3.2–6.4 km•hr−1) and 5 jogging/running stages (8.0–11.3 km•hr−1) was completed in 43 adults (23 ± 5 years, 19♀). Predictors of METs during walking and jogging/running were determined by generalized mixed modeling. The strongest prediction models for walking (R2 = 0.72, P <.001) and jogging/running (R2 = 0.75, P <.001) included cadence2, cadence, step length, age, and leg length (all, P <.001). Step length accounted for 49.1% and 78.3% of model variance during walking and jogging/running, respectively. METs are poorly estimated by cadence during jogging/running but step length reduces error. Strategies to measure step length in free-living settings could better predict physical activity intensity. [ABSTRACT FROM AUTHOR]

The study aimed to examine the effects that L-glutamine supplementation has on quadriceps muscle strength and soreness ratings following eccentric exercise. It was hypothesized that glutamine ingestion would quicken the recovery rate of peak force production and decrease muscle soreness ratings over a 72-hr recovery period. Sixteen healthy participants (8♀/8♂; 22 ± 4 years) volunteered in a double-blind, randomized, placebo-controlled crossover study. Supplement conditions consisted of isoenergetic placebo (maltodextrin, 0.6 g⋅kg-1⋅day-1) and L-glutamine (0.3 g⋅kg-1⋅day-1 + 0.3 g⋅kg-1⋅day-1 maltodextrin) ingestion once per day over 72 hr. Knee extensor peak torque at 0°, 30°, and 180° per second and muscle soreness were measured before, immediately following, 24,48, and 72 hr posteccentric exercise. Eccentric exercise consisted of 8 sets (10 repetitions/set) of unilateral knee extension at 125% maximum concentric force with 2-min rest intervals. L-glutamine resulted in greater relative peak torque at 180°/sec both immediately after (71 ± 8% vs. 66 ± 9%), and 72 hr (91 ± 8% vs. 86 ± 7%) postexercise (all, p < .01). In men, L-glutamine produced greater (p < .01) peak torques at 30°/ sec postexercise. Men also produced greater normalized peak torques at 30°/sec (Nm/kg) in the L-glutamine condition than women (all, p < .05). In the entire sample, L-glutamine resulted in lower soreness ratings at 24 (2.8 ± 1.2 vs. 3.4 ± 1.2), 48 (2.6 ± 1.4 vs. 3.9 ± 1.2), and 72 (1.7 ± 1.2 vs. 2.9 ± 1.3) hr postexercise (p < .01). The L-glutamine supplementation resulted in faster recovery of peak torque and diminished muscle soreness following eccentric exercise. The effect of L-glutamine on muscle force recovery may be greater in men than women. [ABSTRACT FROM AUTHOR]

The activPAL is a valid measure of step counts and posture, but its ability to determine physical activity intensity is unclear. This study tested the criterion validity of the activPAL using its built-in linear cadence-metabolic equivalents (METs) equation (activPAL-linear) versus an individualized height-adjusted curvilinear cadence-METs equation (activPAL-curvilinear) to estimate intensity-related physical activity. Forty adults (25±6 years, 23.3±4.1 kg/m2) wore an activPAL during a 7-stage progressive treadmill walking protocol (criterion: indirect calorimetry). A sub-sample (n=32) wore the device during free-living conditions for 7-days (criterion: PiezoRxD monitor). In the laboratory, the activPAL-linear overestimated METs during slow walking (1.5–3.0 miles•hour−1) but underestimated METs during fast walking (3.5–4.5 miles•hour−1) (all, p<0.001). In the free-living condition, the activPAL-linear overestimated time in light-intensity activity and underestimated moderate-intensity activity (both, p<0.001), but did not register any vigorous-intensity activity. In contrast, the activPAL-curvilinear estimated values statistically equivalent to indirect calorimetry for treadmill stages 1–6 (1.5–4.0 miles•hour−1) and to the PiezoRxD determined light- and moderate-intensity activity during free-living. We present a simple, data processing technique that uses an alternative curvilinear cadence-MET equation that improves the ability of the activPAL to measure intensity-related physical activity in both laboratory and free-living settings. [ABSTRACT FROM AUTHOR]

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The activPAL is a widely-used measure of sedentary time but few studies have evaluated its ability to estimate physical activity intensity. This study determined the accuracy of the algorithm used by the activPAL to predict metabolic equivalents (METs) from cadence and a curvilinear cadence-METs equation individualized for height. Thirty-six healthy adults (25 ± 6 years) completed a progressive walking protocol. Stepping cadence was video recorded and METs were determined via indirect calorimetry. Manually-counted cadence was input into the activPAL and curvilinear equations. The internal activPAL equation overpredicted METs at slower cadences (<120 steps/minute) but underpredicted METs at faster cadences (>120 step/minute) (proportional bias, p <.001). Conversely, the curvilinear equation exhibited neither fixed (p =.37) nor proportional bias (p =.07), and a lower absolute MET difference [0.87 ± 0.65 (range:0.0–3.2) vs. 0.56 ± 0.45 (range:0.0–2.7) METs]. The linear activPAL equation poorly estimates METs from stepping cadence but these inaccuracies may be lessened through the use of an individualized curvilinear equation. [ABSTRACT FROM AUTHOR]

Supplemental digital content is available in the text. Purpose: It is unclear if high-intensity interval training (HIIT) elicits superior improvements in brachial artery (BA) flow-mediated dilation (FMD) responses (i.e., endothelial-dependent vasodilation) than moderate-intensity continuous training (MICT) or resistance training (RT) in otherwise healthy older adults. Whether HIIT enhances lower-limb FMD responses and/or augments low flow-mediated constriction (L-FMC) (endothelial-dependent vasoconstriction) responses more than MICT or RT is also unknown. We tested the hypothesis that HIIT would improve BA and popliteal artery (POP) FMD and L-FMC responses more than MICT or RT in healthy older adults. Methods: Thirty-eight older adults (age, 67 ± 6 yr) performed 6 wk of either HIIT (2 × 20 min bouts alternating between 15-s intervals at 100% of peak power output [PPO] and passive recovery [0% PPO]; n = 12), MICT (34 min at 60% PPO; n = 12), or whole-body RT (8 exercises, 2 × 10 repetitions; n = 14). The L-FMC and FMD were measured before and after training using high-resolution ultrasound and quantified as the percent change in baseline diameter during distal cuff occlusion and after cuff release, respectively. Results: Resting BA blood flow and vascular conductance (both, P < 0.003) were greater after HIIT only. The HIIT and MICT similarly increased BA-FMD (pre–post: both, P < 0.001), but only HIIT improved BA L-FMC (P < 0.001). Both HIIT and MICT similarly enhanced POP FMD and L-FMC responses (both, P < 0.045). Resistance training did not impact FMD or L-FMC responses in either artery (all, P > 0.20). Conclusions: HIIT and MICT, but not RT, similarly improved lower-limb vasodilator and vasoconstrictor endothelial function in older adults. Although HIIT and MICT groups enhanced BA vasodilator function, only HIIT improved resting conductance and endothelial sensitivity to low-flow in the BA. In the short-term, HIIT may be most effective at improving peripheral vascular endothelial function in older adults. [ABSTRACT FROM AUTHOR]