To examine whether the menstrual or monophasic oral contraceptive cycle phases affect submaximal (oxygen uptake (V˙O2) kinetics, maximal lactate steady‐state (MLSS)) and maximal (V˙O2max, ...time‐to‐exhaustion (TTE)) responses to exercise in healthy, active women. During the mid‐follicular or inactive‐pill phase and the mid‐luteal or active‐pill phase of the respective menstrual or oral contraceptive cycle, 15 non‐oral contraceptive users (mean and standard deviation (SD) (±): 27 ± 6 years; 171 ± 5 cm; 65 ± 7 kg) and 15 monophasic oral contraceptive users (24 ± 4 years; 169 ± 10 cm; 68 ± 10 kg) performed: one V˙O2 kinetics test; one ramp‐incremental test; two to three 30‐minute constant‐load cycling trials to determine the power output corresponding to MLSS (MLSSp), followed by a TTE trial. The phase of the menstrual or oral contraceptive cycle did not affect the time constant of the V˙O2 kinetics response (τV˙O2) (mid‐follicular, 20 ± 5 seconds and mid‐luteal, 18 ± 3 seconds; inactive‐pill, 22 ± 8 seconds and active‐pill, 23 ± 6 seconds), V˙O2max (mid‐follicular, 3.06 ± 0.32 L min−1 and mid‐luteal, 3.00 ± 0.33 L min−1; inactive‐pill, 2.87 ± 0.39 L min−1 and active‐pill, 2.87 ± 0.45 L min−1), MLSSp (mid‐follicular, 181 ± 30 W and mid‐luteal, 182 ± 29 W; inactive‐pill, 155 ± 26 W and active‐pill, 155 ± 27 W), and TTE (mid‐follicular, 147 ± 42 seconds and mid‐luteal, 128 ± 54 seconds; inactive‐pill, 146 ± 70 seconds and active‐pill, 139 ± 77 seconds) (P > .05). The rate of perceived exertion (RPE) at minute 30 of the MLSSp trials was greater in the mid‐follicular phase (6.2 ± 1.5) compared with the mid‐luteal phase (5.3 ± 1.4) for non‐oral contraceptive users (P = .022). The hormonal fluctuations between the menstrual and oral contraceptive cycle phases had no detectable effects on submaximal and maximal exercise performance, even when RPE differed.
Critical torque (CT) represents the highest oxidative steady state for intermittent knee extensor exercise, but the extent to which it is influenced by skeletal muscle mitochondria and sex is ...unclear. Vastus lateralis muscle biopsy samples were collected from 12 females and 12 males –matched for relative maximal oxygen uptake normalized to fat‐free mass (FFM) (F: 57.3 (7.5) ml (kg FFM)−1 min−1; M: 56.8 (7.6) ml (kg FFM)−1 min−1; P = 0.856) – prior to CT determination and performance fatiguability trials. Males had a lower proportion of myosin heavy chain (MHC) I isoform (40.6 (18.4)%) compared to females (59.5 (18.9)%; P = 0.021), but MHC IIa and IIx isoform distributions and protein markers of mitochondrial content were not different between sexes (P > 0.05). When normalized to maximum voluntary contraction (MVC), the relative CT (F: 42.9 (8.3)%; M: 37.9 (9.0)%; P = 0.172) and curvature constant, W′ (F: 26.6 (11.0) N m s (N m)−1; M: 26.4 (6.5) N m s (N m)−1; P = 0.962) were not significantly different between sexes. All protein biomarkers of skeletal muscle mitochondrial content, as well as the proportion of MHC I isoform, positively correlated with relative CT (0.48 < r < 0.70; P < 0.05), and the proportion of MHC IIx isoform correlated positively with relative W′ (r = 0.57; P = 0.007). Indices of performance fatiguability were not different between males and females for MVC‐ and CT‐controlled trials (P > 0.05). Greater mitochondrial protein abundance was associated with attenuated declines in potentiated twitch torque for exercise at 60% MVC (P < 0.05); however, the influence of mitochondrial protein abundance on performance fatiguability was reduced when exercise was prescribed relative to CT. Whether these findings translate to whole‐body exercise requires additional research.
Key points
The quadriceps critical torque represents the highest intensity of intermittent knee extensor exercise for which an oxidative steady state is attainable, but its relationship with skeletal muscle mitochondrial protein abundance is unknown.
Matching males and females for maximal oxygen uptake relative to fat‐free mass facilitates investigations of sex differences in exercise physiology, but studies that have compared critical torque and performance fatiguability during intermittent knee extensor exercise have not ensured equal aerobic fitness between sexes.
Skeletal muscle mitochondrial protein abundance was correlated with critical torque and fatigue resistance for exercise prescribed relative to maximum voluntary contraction but not for exercise performed relative to the critical torque.
Differences between sexes in critical torque, skeletal muscle mitochondrial protein abundance and performance fatiguability were not statistically significant.
Our results suggest that skeletal muscle mitochondrial protein abundance may contribute to fatigue resistance by influencing the critical intensity of exercise.
figure legend Critical torque (CT), performance fatiguability, and skeletal muscle mitochondrial protein content and fibre type were determined for males (M) and females (F) matched for peak oxygen uptake (V̇O2peak${\dot{V}}_{{\mathrm{O}}_{2}\mathrm{peak}}$) per fat‐free mass. The CT and mitochondrial protein content were not significantly different between sexes. Mitochondrial protein content correlated with CT but not the curvature constant, W′. Mitochondrial protein content correlated with fatiguability when intermittent, isometric knee extensor exercise was performed to task failure at 60% MVC but not when it was performed for 30 min 10% below CT.
New Findings
What is the central question of this study?
What are the effects of the menstrual (early follicular and mid‐luteal) or monophasic oral contraceptive (inactive‐ and active‐pill) cycle ...phases on vascular reperfusion of lower limb microvasculature in healthy, active women using the near‐infrared spectroscopy (NIRS) vascular occlusion test (VOT) technique?
What is the main finding and its importance?
We demonstrated that vascular responsiveness in the lower limb microvasculature remained unchanged between the early follicular and mid‐luteal phases of the menstrual cycle and inactive‐ and active‐pill phases of the oral contraceptive cycle. These data support that controlling for the cycle phases, within the specific times evaluated in this study, might not be necessary when assessing NIRS‐VOT reperfusion rates.
The objective was to examine whether the menstrual or monophasic oral contraceptive cycle phases affect microvascular responsiveness of the lower limb in healthy, active women. During the follicular or inactive‐pill phase and the luteal or active‐pill phase of the menstrual or oral contraceptive cycle, respectively, 15 non‐oral contraceptive users (mean ± SD; 27 ± 6 years of age) and 15 monophasic oral contraceptive users (24 ± 4 years of age) underwent a lower‐limb vascular occlusion test (5 min baseline, 5 min occlusion and 8 min post cuff release). Menstrual cycle phases were verified using an ovulation test. Vascular responsiveness was assessed by calculating the near‐infrared spectroscopy‐derived muscle oxygen saturation (StO2) reperfusion slope (slope 2 StO2) and the post occlusion StO2 area under the curve (StO2AUC) of the tibialis anterior muscle. There were no differences in the reperfusion slope (as a percentage per second; follicular, 1.18 ± 0.48; luteal, 1.05 ± 0.48, inactive‐pill, 0.95 ± 0.23; and active‐pill, 0.87 ± 0.36; P = 0.09) and area under the curve (as a product of the percentage and seconds; follicular, 1067 ± 562; luteal, 918 ± 414, inactive‐pill, 945 ± 702; and active‐pill, 750 ± 519; P = 0.09) between the phases of the menstrual or oral contraceptive cycle, regardless of pill generation. The duration of oral contraceptive use was not associated with changes in slope 2 StO2 (r = 0.02, P = 0.94) or StO2AUC (r = −0.34, P = 0.22) between cycle phases. In conclusion, vascular responsiveness remained unchanged between the early follicular and mid‐luteal phases of the menstrual cycle and the inactive‐pill and active‐pill phases of the oral contraceptive cycle.
The restrictions introduced in response to the COVID-19 pandemic affected the regular routines of Canadians, including access to play and physical activity opportunities, while limiting social ...connections. In response to this, a recreation centre created take-home play kits that contained loose parts with the aim of facilitating unstructured play. Between August 2021 and January 2022, ten parents participated in semi-structured interviews via telephone or videoconferencing platforms that captured their experiences of the take-home play kits. Using Thematic Analysis, we identified themes and subthemes reflecting parent perceptions and experiences of the take-home play kit. Three themes emerged: (1 A forced renaissance of play; (2) Bringing unstructured play home, and; (3) Parenting is child's play. Parents shared how the pandemic resulted in decreased physical activity and social opportunities for their children. The parents described how the take-home play kits supported unstructured play as well as their perspectives on the importance of unstructured play. Parents in our study suggested that a take-home loose parts play kit could be a useful resource to help engage children in unstructured play in both indoor and outdoor environments.
BACKGROUND: Low levels of physical activity and increased participation in sedentary leisure-time activities are two important obesity-risk behaviors that impact the health of today’s youth. Friend’s ...health behaviors have been shown to influence individual health behaviors; however, current evidence on the specific role of friendship networks in relation to levels of physical activity and sedentary behavior is limited. The purpose of this review was to summarize evidence on friendship networks and both physical activity and sedentary behavior among children and adolescents. METHOD: After a search of seven scientific databases and reference scans, a total of thirteen articles were eligible for inclusion. All assessed the association between friendship networks and physical activity, while three also assessed sedentary behavior. RESULTS: Overall, higher levels of physical activity among friends are associated with higher levels of physical activity of the individual. Longitudinal studies reveal that an individual’s level of physical activity changes to reflect his/her friends’ higher level of physical activity. Boys tend to be influenced by their friendship network to a greater extent than girls. There is mixed evidence surrounding a friend’s sedentary behavior and individual sedentary behavior. CONCLUSION: Friends’ physical activity level appears to have a significant influence on individual’s physical activity level. Evidence surrounding sedentary behavior is limited and mixed. Results from this review could inform effective public health interventions that harness the influence of friends to increase physical activity levels among children and adolescents.
•One-third of parents were extremely or very anxious about the COVID-19 pandemic.•Parents reported increases in children’s sedentary behaviour during COVID-19.•Children’s play at parks and public ...spaces decreased during COVID-19.•Children’s spent less time with friends indoors and outdoors during COVID-19.•Children of high anxiety parents had fewer park visits and higher computer use.
The public health emergency response to the COVID-19 virus has involved physical distancing strategies to reduce person-to-person transmission. Pandemics, including COVID-19, may influence changes to physical activity and sedentary behaviours among children. However, the role of parent anxiety related to COVID-19 on children’s physical activity and sedentary behaviours has yet to be explored. The purpose of this study was to examine the associations between parent COVID-19 anxiety and physical activity and sedentary behaviours among school-aged children (5–17 years) and; to describe these behaviour patterns among school-aged children in relation to the COVID-19 public health emergency response. Between April and June 2020, a random sample of adults (Calgary, Canada) completed an online questionnaire. This sample included 345 parents of at least one school-aged child (80.5% aged 5 to 11 years and 54.9% male). Approximately one-third of parents (35.7%) reported being extremely or very anxious about COVID-19. During this period, most children increased television watching (58.8%), computing or gaming (56.4%), and use of screen-based devices (75.9%). Not surprisingly, given the mandated closure of playgrounds, approximately one-half of children decreased playing at the park (52.7%) and in public spaces (53.7%). Children’s physical activity at home either increased (48.8%) or remained unchanged (32.9%). Children of more anxious parents had fewer visits to the park and were more likely to spend ≥2 h/day computing or gaming compared with children of less anxious parents. Strategies to counteract the unintended consequences of the COVID-19 public health measures on parent and child wellbeing are needed.
Introduction
Mild obesity has been associated with postprandial brachial artery vascular dysfunction. However, direct assessment of these effects within the forearm skeletal muscle microcirculation ...remains unclear. Thus, this study aimed to investigate the effects of mild obesity on the arm micro‐ and macrovascular responses to glucose ingestion.
Methods
This cross‐sectional study combined NIRS assessments of forearm skeletal muscle (FDS) reactivity (reperfusion slope) with %FMD of conduit artery function (brachial artery) before (Pre), as well as 60 and 120 min after glucose ingestion in 10 lean (BMI 23.9 ± 1.8) and 10 obese (BMI 32.9 ± 1.9) individuals.
Results
Both groups showed a significant increase in the reperfusion slope at 60 and 120 min after glucose ingestion compared with the pre–glucose ingestion measurements. Obese individuals showed a significant (p < .05) reduction in %FMD at 60 min after glucose ingestion, while no significant changes in postprandial %FMD were observed in lean participants.
Conclusion
Even though obese individuals showed impaired postprandial brachial artery function, the current findings suggest that mild obesity does not affect the forearm skeletal muscle responses to glucose ingestion.
Physical activity supportive environments have the potential to promote health-related fitness in adults. However, the extent to which neighbourhood built characteristics promote health-related ...fitness via physical activity has received little research attention. Therefore, our objective was to estimate the indirect and direct effects between neighbourhood built characteristics and health-related fitness mediated by physical activity.
Using cross-sectional data collected between 2014 and 2019, we merged neighbourhood built characteristics, physical activity, and health-related fitness variables, derived from two Canadian national databases. Using these data, we estimated sex-stratified covariate-adjusted path models (males: n = 983 to 2796 and females: n = 962 to 2835) to assess if accelerometer-measured light, moderate, and vigorous intensity physical activity mediated associations between objectively measured neighbourhood built characteristics (intersection density, dwelling density, points of interest, and transit density) and health-related fitness (grip strength, jump height, V̇O2max, and flexibility). Across 16 sex-specific models, we estimated 48 indirect and 16 direct effects.
Concerning significant associations, for males we found that 16.6% of indirect and 18.8% of direct were negative and 4.2% of indirect and 0% of direct were positive. For females, we found that 12.5% of indirect and 0% of direct were negative and 0% of indirect and 25% of direct effects were positive.
Individual Canadian Active Living Environment built characteristics are positively associated with moderate-intensity physical activity and negatively associated with light-intensity physical activity. Further, associations between activity friendly neighbourhood characteristics and health related-fitness may be distinct from physical activity.
•Built characteristics (BCs) and health-related fitness (HRF) were related (BC-HRF).•Direct effects were found between BCs and grip strength in males.•Direct effects were found between BCs, V̇O2max, and flexibility in females.•BC-HRF associations varied by type of BC, activity intensity, and component of HRF.
Objectives: To investigate stress levels among Canadian female university students and determine cutoff scores for low, moderate, and high stress in this population. Participants: Hundred female ...undergraduates, mean age of 20.3 (SD = 1.8) years. Methods: A cross-sectional design was employed and students were approached in hallways at the start of the 2018 academic year and asked to complete a Student-life Stress Inventory (SSI). Results: Mean stress score was 138.2 (SD = 28.9) out of 255; 53% reported high exposure to stress with 80% reporting low behavioral response to stress. Conclusion: Self-report exposure to stress was high in many at the semester start but manageable and stress scores were similar to other campuses that administered the SSI. A study design that uses qualitative data to enhance the survey findings while longitudinal tracking over the academic year may better inform the extent of student stress exposure and how students effectively cope with this exposure.
Muscular strength and body composition are important components of health-related fitness (HRF). Grip strength and body fat percent, in particular, are associated with chronic disease and affected by ...health behaviours. Evidence suggests relationships between the neighbourhood built environment (BE) and HRF exist, however, few studies have focused on grip strength and body fat percent. Therefore, our study aimed to estimate the sex-specific associations between the neighbourhood BE, grip strength, and body fat percent among urban-dwelling Canadian adults.
We analyzed cross-sectional survey and HRF data collected in 2011-2015 from 4052 males and 7841 females (Alberta's Tomorrow Project, Canada). Grip strength and body fat percent were measured via handgrip dynamometry and bioelectrical impedance analysis, respectively. Walkability (Canadian Active Living Index) and greenness (Normalized Difference Vegetation Index) estimates were linked to participant data. Sex-stratified covariate-adjusted linear regression models estimated the associations between the BE and HRF variables.
Walkability was negatively associated with grip strength and body fat percent in males (β -0.21, 95%CI: -0.31 to -0.11 and β -0.08, 95%CI: -0.15 to -0.02, respectively) and females (β -0.06, 95%CI: -0.10 to -0.01 and β -0.08, 95%CI: -0.14 to -0.02, respectively). Greenness was positively associated with grip strength in males (β 6.99, 95%CI: 3.62 to 10.36) and females (β 2.72, 95%CI: 1.22 to 4.22) but not with body fat percent. Controlling for physical activity and sitting did not attenuate these associations.
Characteristics of the neighbourhood BE appear to be associated with muscular strength and body composition, independent of physical activity and sedentary behaviour.
•Walkability and greenness are associated with body fat percent and grip strength.•Associations are not attenuated by adjustment for physical activity or sitting time.•Associations are present for both males and females.•Grip strength associations were robust to different greenness buffer sizes.•Our results may inform the design of health-supportive neighbourhoods.
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