Higher habitual lying time is inversely associated with vagal-related heart rate variability outcomes in younger adults.

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.

Validity of ActivPAL CREA software detection of sitting and lying during free-living conditions.

Objective. Approaches to differentiate sitting and lying are available within the default activPAL software from a single thigh-worn monitor. Dual-monitor methods use multiple monitors positioned on the thigh and torso to characterize sitting versus lying. We evaluated the validity between these two methods to measure waking, sitting, and lying time in free-living conditions. We also examined if the degree-threshold distinguishing sitting/lying for the dual-monitor (<30° and <45°) impacted results.Approach. Thirty-five young adults (24 ± 3 years, 16 females) wore an activPAL 24 h per day on their thigh and torso during free-living conditions (average: 6.8 ± 1.0 d, 239 total). Data were processed using the default activPAL software (thigh-only) or a custom MATLAB program (dual-monitor).Main results. The single-monitor recorded less lying time (59 ± 99 min d-1) and more sitting time (514 ± 203 min d-1) than the dual-monitor method regardless of 30° (lying: 85 ± 94 min d-1; sitting: 488 ± 166 min d-1) or 45° lying threshold (lying: 170 ± 142, sitting: 403 ± 164 min d-1; all,p< 0.001). The single monitor lying time was weakly correlated to the dual-monitor (30°:ρ= 0.25, 45°:ρ= 0.21; both,p< 0.001), whereas sitting was moderate-strong (30°:ρ= 0.76, 45°:ρ= 0.58; both,p< 0.001). However, the mean absolute error was 81 min d-1(30°) and 132 min d-1(45°) for both lying and sitting.Significance. The method of differentiating sitting/lying from a single thigh-worn activPAL records more sitting time and less lying time compared to a dual-monitor configuration (regardless of degree-threshold) that considered the position of the torso. A further refinement of algorithms or implementation of multiple-monitor methods may be needed for researchers to derive detailed sedentary positions.

More moderate-intensity physical activity and less prolonged sedentary time are associated with better very short-term systolic blood pressure variability in healthy adults.

Whole-day movement guidelines for improving health, recommend that adults engage in at least 150 min week-1 of moderate-to-vigorous aerobic physical activity and limit their sedentary time. In young adults, higher systolic blood pressure variability (BPV) is a precursor for the development of hypertension. The impact of habitual activity that comprises (inter)national guidelines on BPV is unclear. We tested the hypothesis that less habitual physical activity and greater sedentary time would be associated with larger BPV. Ninety-two normotensive participants [age: 19-38 years, body mass index (BMI): 23.6 ± 3.3 kg/m2, 44♀] wore an activPAL monitor on their thigh for 7.0 ± 0.3 days. Ten minutes of supine systolic arterial pressure was measured via finger photoplethysmography (115 ± 11 mmHg). Beat-by-beat systolic BPV was measured using the average real variability index (1.1 ± 0.6 mmHg). Relationships between habitual activity outcomes and BPV were assessed via multiple regressions adjusted for age, sex, and BMI. Moderate-intensity physical activity (average: 36 ± 19 min day-1; ß = -0.010, p = 0.02) and time spent in sedentary bouts >1-h (245 ± 134 min day-1; ß = 0.002, p < 0.001), but not light-intensity activity, vigorous-intensity activity, standing time, sedentary breaks, or time spent in sedentary bouts <1-h (all, p > 0.10) were predictors of systolic BPV. Higher moderate physical activity and lower prolonged sedentary time were associated with attenuated systolic BPV responses in young adults. These findings highlight the cardiovascular benefits of habitual activity among younger adults and suggest that simple strategies such as reducing long periods of uninterrupted sitting and increasing moderate-intensity physical activity may be efficacious for reducing the risk of developing or delaying the onset of hypertension.

Characterization of Detailed Sedentary Postures Using a Tri-Monitor ActivPAL Configuration in Free-Living Conditions.

Objective monitors such as the activPAL characterize time when the thigh is horizontal as sedentary time. However, there are physiological differences between lying, bent-legged sitting, and straight-legged sitting. We introduce a three-monitor configuration to assess detailed sedentary postures and demonstrate its use in characterizing such positions in free-living conditions. We explored time spent in each sedentary posture between prolonged (>1 h) versus non-prolonged (<1 h) sedentary bouts. In total, 35 healthy adults (16♀, 24 ± 3 years; 24 h/day for 6.8 ± 1.0 days) wore an activPAL accelerometer on their thigh, torso, and shin. Hip and knee joint flexion angle estimates were determined during sedentary bouts using the dot-product method between the torso−thigh and thigh−shin, respectively. Compared to lying (69 ± 60 min/day) or straight-legged sitting (113 ± 100 min/day), most time was spent in bent-legged sitting (439 ± 101 min/day, p < 0.001). Most of the bent-legged sitting time was accumulated in non-prolonged bouts (328 ± 83 vs. 112 ± 63 min/day, p < 0.001). In contrast, similar time was spent in straight-legged sitting and lying between prolonged/non-prolonged bouts (both, p > 0.26). We document that a considerable amount of waking time is accumulated in lying or straight-legged sitting. This methodological approach equips researchers with a means of characterizing detailed sedentary postures in uncontrolled conditions and may help answer novel research questions on sedentariness.

Impact of habitual sedentary patterns on popliteal artery endothelial-dependent vasodilation in healthy adults.

INTRODUCTION: Acute, laboratory-based bouts of prolonged sitting attenuate lower-limb arterial endothelial-dependent vasodilation. However, the impact of habitual sedentary patterns on popliteal artery endothelial health is unclear. We tested the hypothesis that greater habitual total sedentary time, more time spent in prolonged sedentary bouts, and fewer sedentary breaks would be associated with worse popliteal flow-mediated dilation (FMD) responses. METHODS: This cross-sectional study used 98 healthy participants (19-77 years, 53 females) that wore an activPAL monitor on the thigh for 6.4 ± 0.8 days to objectively measure sedentary activity and completed a popliteal ultrasound assessment to determine FMD. Both relative (%baseline diameter) and absolute (mm) FMD were calculated. Using bivariate correlation and multiple regression analyses, we examined if there were relationships between sedentary outcomes and FMD while statistically controlling for any potential confounders. RESULTS: In the multiple regression model, age (p = 0.006, ß = -0.030, 95% CI = -0.051, -0.009) and total time in sedentary bouts > 1 hour (p = 0.031, ß = -0.005, 95% CI = -0.009, -0.001) were independent predictors of relative FMD. Age (ß = -0.002, 95% CI = -0.003, -0.001), mean blood flow (ß = 0.013, 95% CI = 0.002, 0.024), moderate-intensity physical activity (ß = 155.9E-5, 95% CI = 22.4E-5, 289.4E-5), sedentary breaks (ß = 0.036, 95% CI = 0.007, 0.066), and total time spent in sedentary bouts > 1 hour (ß = -25.02E-5, 95% CI = -47.67E-5, -2.378E-5) were predictors of absolute FMD (all, p < 0.047). All independent outcomes remained significant after partially controlling for all other predictor variables (all, p < 0.031). CONCLUSIONS: Habitual prolonged sedentary bouts and sedentary breaks, but not total sedentary time, were predictors of popliteal endothelial-dependent vasodilatory function. The patterns by which sedentary time is accumulated may be more important than the total sedentary time on lower-limb arterial health.

The role of at home workstation ergonomics and gender on musculoskeletal pain.

BACKGROUND: The recent mandate for university faculty and staff to work-from-home (WFH) during the COVID-19 pandemic has forced employees to work with sub-optimal ergonomic workstations that may change their musculoskeletal discomfort and pain. As women report more work-related musculoskeletal discomfort (WMSD), this effect may be exacerbated in women. OBJECTIVE: The purpose of this study was to describe university employee at-home office workstations, and explore if at-home workstation design mediates the effect of gender on musculoskeletal pain. METHODS: University employees completed a survey that focused on the WFH environment, at home workstation design and musculoskeletal pain. Descriptive statistics and regression analysis were used to analyze the responses. RESULTS: 61% of respondents reported an increase in musculoskeletal pain, with the neck, shoulders and lower back being reported most frequently. Women reported significantly greater musculoskeletal pain, but this relationship was significantly mediated by poor ergonomic design of the home workstation. Improper seat-height and monitor distance were statistically associated with total-body WMSD. CONCLUSIONS: WFH has worsened employee musculoskeletal health and the ergonomic gap between women and men in the workspace has persisted in the WFH environment, with seat height and monitor distance being identified as significant predictors of discomfort/pain.

Comparison of habitual stepping cadence analysis methods: Relationship with step counts.

BACKGROUND: Different approaches have been implemented to calculate stepping cadence (steps/min) that vary in the time demominator used. Given the differences in how stepping intensity are calculated, it is unclear if they are more so associated with total step counts. RESEARCH OBJECTIVE: This study compared three methods of calculating stepping cadence and determined their relationship with total step counts. METHODS: 132 participants (74♀; 35 ± 20 years; body mass index: 24.9 ± 4.0 kg•m-2) wore an activPAL monitor 24-hr/day for up to 8-d (total: 869-d). The total steps/day, time spent stepping (0.1 s resolution; to calculate bout stepping rate), time spent stepping in 60 s epochs (step accumulation), and awake time (awake cadence) were determined. Each cadence method (in steps/min) were compared via Spearman's rank correlation. The relationships versus total step count were determined, and the strength of these relationships compared between cadence measures (95% confidence interval of correlation differences). RESULTS: Bout stepping rate (85 ± 14 steps/min) was larger than step accumulation (34 ± 12 steps/min) and awake cadence (10 ± 5 steps/min, both: P < 0.001). Step accumulation was positively strongly related to bout stepping rate (ρ = 0.813; P < 0.001) whereas awake cadence was weakly related to bout stepping rate (ρ = 0.496; P < 0.001). Step accumulation (ρ = 0.634; P < 0.001) and awake cadence (ρ = 0.964; P < 0.001) were more related to step counts than bout stepping rate (ρ = 0.497; P < 0.001; 95% confidence intervals of correlation differences: step accumulation=0.10-0.17, awake cadence: 0.42-0.52). SIGNIFICANCE: Without a precise measure of time spent stepping, stepping cadence is lower using the step accumulation and awake cadence methods. Step accumulation and awake cadence are more related to total step counts than bout stepping rate. Bout stepping rate outcomes reflect continuous stepping rate, does not rely on a preset epoch, and may have less overlap with step counts, which may have implications for determining the unique contributions of step count versus stepping cadence on health outcomes.

Habitual sedentary time and stationary time are inversely related to aerobic fitness.

A one metabolic-equivalent-of-task increase in peak aerobic fitness (peak MET) is associated with a clinically relevant improvement in survival risk and all-cause mortality. The co-dependent impact of free-living physical behaviours on aerobic fitness are poorly understood. The purpose of this study was to investigate the impact of theoretically re-allocating time spent in physical behaviours on aerobic fitness. We hypothesized that substituting sedentary time with any physical activity (at any intensity) would be associated with a predicted improvement in aerobic fitness. Peak volume rate of oxygen uptake ( V ˙ O2peak) was assessed via indirect calorimetry during a progressive, maximal cycle ergometer protocol in 103 adults (52 females; [38 ±â€¯21] years; [25.0 ±â€¯3.8] kg/m2; V ˙ O2peak: [35.4 ±â€¯11.5] ml·kg-1·min-1). Habitual sedentary time, standing time, light- (LPA), moderate- (MPA), and vigorous-physical activity (VPA) were assessed 24-h/day via thigh-worn inclinometry for up to one week (average: [6.3 ±â€¯0.9] days). Isotemporal substitution modelling examined the impact of replacing one physical behaviour with another. Sedentary time (ß = -0.8, 95% CI: [-1.3, -0.2]) and standing time (ß = -0.9, 95%CI: [-1.6, -0.2]) were negatively associated with V ˙ O2peak, whereas VPA was positively associated with relative V ˙ O2peak (ß = 9.2, 95%CI: [0.9, 17.6]). Substituting 30-min/day of VPA with any other behaviour was associated with a 2.4-3.4 higher peak MET. Higher standing time was associated with a lower aerobic fitness. As little as 10-min/day of VPA predicted a clinically relevant 0.8-1.1 peak MET increase. Theoretically, replacing any time with relatively small amounts of VPA is associated with improvements in aerobic fitness.

The Perceived Demands of Ice Hockey Goaltending Movements on the Hip and Groin Region: An Elite Coach and Player Perspective.

BACKGROUND: Many ice hockey goaltending techniques force hip joints and groin muscles into extreme ranges of motion, which may increase the risk of hip and groin problems. PURPOSE: To explore how elite goaltenders and goaltending coaches perceive the demands of common goaltending techniques on the hip and groin region. We further explored differences in perception between goaltenders and their coaches as well as between junior (age <20 years) and senior (age ≥20 years) goaltenders. STUDY DESIGN: Cross-sectional survey. METHODS: We developed a model to categorize common ice hockey goaltending techniques into quantifiable units and invited elite goaltenders and coaches in Sweden to complete an online survey. Participants were asked to rate the perceived demands of each technique on the hip and groin using a Likert scale (not at all, slightly, somewhat, very, or extremely demanding). Using the chi-square test, the proportion of participants perceiving each technique as very or extremely demanding were compared between goaltenders and coaches as well as between senior and junior goaltenders. RESULTS: We received responses from 132 goaltenders and 43 coaches. The stances most frequently perceived as very or extremely demanding were the reverse vertical horizontal post-play (40%) and the butterfly save (25%). Among transitions, movements into the post were most frequently rated as very or extremely demanding (11%-40%). Several techniques were perceived as demanding by a larger share of coaches than goaltenders (difference, 13%-46%; P < .001-.028) and a larger share of senior versus junior goaltenders (difference, 12%-20%; P = .13-.18). CONCLUSION: The post-play and the butterfly were the goaltending techniques most frequently perceived as demanding, and more coaches than goaltenders percieved these techniques demanding. The results of this study may inform injury prevention efforts for ice hockey goaltending.

The influence of habitual breaks in sedentary time on cardiovagal baroreflex function.

Sedentary time has recently been included in the 24-h activity guidelines. However, the impact of habitual sedentary patterns on autonomic cardiovascular regulation are unclear. We tested the hypothesis that more sedentary time and fewer sedentary breaks were associated with lower cardiovagal baroreflex sensitivity. More frequent sedentary breaks, but not total sedentary time, was independently and positively associated with vagally mediated blood pressure control. Breaking up sedentary time could be more important than total sedentary time for cardiovascular health. Novelty: Breaks in sedentary time is an independent predictor of cardiovagal baroreflex sensitivity, with more frequent breaks associated with better vagally mediated blood pressure regulation.

Pacing strategies and relationships between speed and stroke parameters for elite sprint kayakers in single boats.

The study aimed to determine the pacing strategies of elite single-boat sprint kayakers, as well as the relationships between stroke parameters (stroke rate (SR) and stroke length (SL)) and kayak speed throughout the race. High-resolution split speed and stroke parameter data from men's (MK1) and women's (WK1) single-boat A- and B-finals in 2016-2017 international sprint kayak competitions were analysed. Correlation coefficients were calculated between SR-speed and SL-speed during each split for each race group. Athletes followed all-out, positive and seahorse-shaped pacing strategies for the 200 m, 500 m and 1000 m races, respectively. SL-speed had greater correlations during the first half of the MK1 200 m race, whereas SR-speed had greater correlations during the second half. SR-speed correlations were greater than SL-speed correlations throughout the final 150 m of WK1 200 m races. There were large and very large correlations between SR-speed at the end of both the WK1 500 m and MK1 1000 m race distances, respectively, despite following different pacing strategies. Single-boat pacing strategies change due to race distance during major international sprint kayak competitions, whereas the relationships between stroke parameters and speed change depending on athlete sex and the race distance.

The Bout Cadence Method Improves the Quantification of Stepping Cadence In Free-Living Conditions.

BACKGROUND: Existing analytical approaches used to measure free-living stepping cadence (steps per minute; spm) characterize stepping two-ways: 1) 60 s epochs without considering time spent stepping during the epoch (step accumulation; SA), or 2) a bout-based analysis that considers both number of steps and time spent stepping during stepping bouts (total event cadence; TEC). SA and TEC may incorrectly characterize cadence in epochs that do not consist of continuous stepping or if there are marked changes in cadence within a stepping bout, respectively. RESEARCH QUESTION: How does a bout-based analytical method that examines each stepping bout individually and considers within-bout changes in stepping cadence during epochs ≥120 s (Bout Cadence; BC) compare to SA and TEC? METHODS: ActivPAL™-derived data from 122 participants were analyzed (790 total days). SA and TEC were calculated according to previous literature. BC calculated cadence bout-by-bout and stride-by-stride for bouts lasting <120 s and ≥120 s, respectively. Time spent stepping between 0-140 spm (divided into 20 spm bins) or >140 spm were determined for each method. Time spent in slow (0-80 spm), medium (80-120 spm) and fast (>120 spm) cadences for each method were compared via Bland-Altman analyses. RESULTS: Almost half (43 %) of the total number of 60 s epochs included ≥2 stepping bouts, and 37 % of total stepping time was accumulated in continuous stepping bouts ≥120 s. Compared to TEC, BC identified more daily time spent in the 20-40 spm and >120 spm cadence bins, but less time spent in the 60-120 spm range. Both SA (fixed bias: -11.0 ± 12.4 min/day) and TEC (fixed bias: -10.0 ± 13.6 min/day) underestimated faster stepping cadences compared to BC. SIGNIFICANCE: Existing analytical approaches largely underestimate faster stepping cadences, resulting in inaccurate measurements of vigorous-intensity stepping activity. The BC better characterizes higher intensity stepping activity, which could have important implications for assessing participants' true habitual stepping activity levels.

Meeting international aerobic physical activity guidelines is associated with enhanced cardiovagal baroreflex sensitivity in healthy older adults.

PURPOSE: Cardiovagal baroreflex sensitivity (cvBRS) reflects the efficiency of modulating heart rate in response to changes in systolic blood pressure. International guidelines recommend that older adults achieve at least 150 min of moderate-vigorous physical activity per week. We tested the hypothesis that older adults who achieve these guidelines will exhibit greater cardiovagal baroreflex sensitivity versus those who do not. METHODS: A cross-sectional comparison of older adults who did (active, 66 ± 5 years, 251 ± 79 min/week; n = 19) and who did not (inactive, 68 ± 7 years, 89 ± 32 min/week; n = 17) meet the activity guidelines. Beat-by-beat R-R intervals (electrocardiography) and systolic blood pressure (finger photoplethysmography) were recorded. Spontaneous cardiovagal baroreflex sensitivity was assessed using the sequence technique from 10 min of resting supine data. Cardiovagal baroreflex function was also measured during early phase II and phase IV of the Valsalva maneuver. Peak oxygen uptake was determined during maximal cycle ergometry. Moderate-vigorous intensity physical activity and time spent sedentary were assessed over 5 days using the PiezoRx and activPAL, respectively. RESULTS: Groups had similar peak oxygen uptake (active 25 ± 9 vs. inactive 22 ± 6 ml/kg/min; p = 0.218) and sedentary time (active 529 ± 60 vs. inactive 568 ± 88 min/day; p = 0.130). However, the active group had greater (all, p < 0.019) cvBRS at rest (9.1 ± 2.7 vs. 5.0 ± 1.9 ms/mmHg), during phase II (8.2 ± 3.8 vs. 5.4 ± 2.1 ms/mmHg), and during phase IV (9.9 ± 3.8 vs. 5.6 ± 1.6 ms/mmHg). In the pooled sample, moderate-vigorous physical activity was positively correlated (all, p < 0.015) with spontaneous (R = 0.427), phase II (R = 0.447), and phase IV cvBRS (R = 0.629). CONCLUSIONS: Independent of aerobic fitness and sedentary time, meeting activity guidelines was associated with superior cardiovagal baroreflex sensitivity at rest and during the Valsalva maneuver in older adults.

Development and verification of a protocol to quantify hip joint kinematics: an evaluation of ice hockey goaltender pads on hip motion.

BACKGROUND: The butterfly save technique is commonly used by ice hockey goaltenders and has recently been identified as a potential mechanism for hip joint injuries due to the extreme body positions involved. Unfortunately, commonly used kinematic marker sets that determine these body positions are heavily influenced by skin motion artifact and are obscured by protective equipment, making it difficult to obtain reliable measures of hip motion. PURPOSE: To create a new kinematic protocol that could be used when protective equipment prevents typical marker placements and to use this protocol to quantify hip kinematics and butterfly performance in 4 different goalie pad conditions. STUDY DESIGN: Controlled laboratory study. METHODS: A new marker set consisting of marker clusters attached to the lateral thigh and posterior leg was developed. This marker set was verified by evaluating the root mean square (RMS) difference between the developed testing marker set and the calibrated anatomic systems technique marker set during passive range of motion (ROM) tests. The testing marker set was then used in a repeated-measures study in which 12 junior goaltenders performed 5 butterfly movements on synthetic ice, in 4 different goalie pad conditions (control, flexible-wide leg channel, flexible-tight leg channel, and stiff-wide leg channel). RESULTS: The grouped RMS differences and SDs calculated during verification were 1.43° ± 0.41°, 1.0° ± 0.39°, and 3.32° ± 1.32° for hip flexion-extension, abduction-adduction, and internal-external rotation, respectively. There was no significant main effect of goal pad condition on the peak amount of hip internal rotation; however, there was a significant main effect of goal pad condition on the butterfly width (P = .022). Post hoc comparisons revealed that the butterfly width was significantly smaller in the control pad condition compared with the flexible-tight pad condition (P = .03). CONCLUSION: The new marker set enabled measurements of hip joint kinematics while subjects are wearing protective equipment that are not possible with other marker sets. Interindividual variations in performance of the butterfly technique influenced the amount of hip internal rotation achieved; however, on average, goaltenders exceeded their active internal ROM during butterfly movements. CLINICAL RELEVANCE: Exceeding internal rotation range of hip motion may make goaltenders susceptible to hip injuries such as femoral acetabular impingement.

Investigating cervical muscle response and head kinematics during right, left, frontal and rear-seated perturbations.

OBJECTIVE: Whiplash research has largely focused on rear collisions because they account for the majority of whiplash injuries. The purpose of this study was to evaluate the effects of 4 perturbation directions (anterior, posterior, right, and left) on muscle activity and head kinematics to provide insight into the whiplash mechanism of injury. METHODS: The effects of 4 perturbation directions induced by a parallel robotic platform, with peak acceleration of 8.50 m/s2, were analyzed on 10 subjects. Surface electromyography (EMG) measures were collected from the sternocleidomastoid (SCM), trapezius, and splenius capitus muscles. Kinematics of the head, thorax, and head relative to thorax were also measured. RESULTS: We observed stereotypic responses for kinematics and SCM EMG for the various perturbation directions; the trapezius and splenius capitus muscles showed amplitudes that were less than 5 percent maximum voluntary contraction (MVC). Rear perturbations elicited the smallest onset latencies for the SCM (30 ms) and kinematic variables and greatest linear head center of mass (COM) accelerations. Frontal perturbations resulted in an average SCM onset latency of 143 ms and demonstrated the greatest magnitude of head translations and rotations relative to the thorax. Left and right perturbations demonstrated similar kinematics and SCM onset latencies (55 and 65 ms, respectively). CONCLUSIONS: Compared to frontal, left, and right directions, rear perturbations showed smaller SCM onset latencies, greater SCM amplitudes, and larger head accelerations, relating to a greater potential for injury. We suggest that the greater contact area and stiffness of the seatback, in the posterior direction, compared to restrictions in other directions, led to increased peak head accelerations and shorter SCM onset latencies.