Estimating Energy Expenditure during Level, Uphill, and Downhill Walking
Medicine & Science in Sports & Exercise. ., Post Acceptance: April 09, 2019
Abstract:
Introduction
The Load Carriage Decision Aid (LCDA) walking equation was developed from literature-aggregated group mean data to calculate standing and level walking energy expenditures in healthy, military-age adults. The LCDA walking equation has not been validated for use in individuals or graded walking.
Purpose
We aimed to validate the LCDA walking equation as a predictor of standing and level walking energy expenditure in individuals and expand to a new graded walking equation for uphill and downhill walking.
Methods
We compiled standing, level walking, and graded walking energy expenditures measured in 95 participants from eleven studies. Walking speeds reached up to 1.96 m·s -1 with grades ranging between -40% and 45%. The LCDA walking equation was validated against the aggregated standing and level walking data. The new LCDA graded walking equation was developed and cross-validated on the graded walking trials. We compared each equation against four reference predictive equations with the standard error of estimation (SEE) as the primary criterion.
Results
The LCDA walking equation accurately estimated standing and level walking energy expenditure (Bias, -0.02 ± 0.20 W·kg -1 ; SEE, 0.20 W·kg -1 ). Addition of the novel grade term resulted in precise estimates of uphill and downhill walking energy expenditure (Bias, 0.09 ± 0.40 W·kg -1 ; SEE, 0.42 W·kg -1 ).
Conclusions
The LCDA walking equation is a valid predictor of standing and walking energy expenditure in healthy, military-age individuals. We developed a novel grade term for estimating both uphill and downhill walking energy expenditure with a single equation. Practitioners can use the new LCDA graded walking equation to calculate energy expenditure during standing as well as walking on level, uphill, and downhill slopes.
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Kinetics of Left Ventricular Mechanics during Transition from Rest to Exercise
Medicine & Science in Sports & Exercise. ., Post Acceptance: April 09, 2019
Abstract:
At the onset of physical exercise, oxygen (O 2 ) transport adapts to meet the working muscle O 2demands. Cardiac output abruptly increases through the concomitant changes of heart rate and stroke volume (SV), which is conditioned by the left ventricular (LV) function. The purpose of this study was to investigate the contribution of many LV diastolic and systolic function parameters, including twist-untwist mechanics, to SV adaptation during the first minutes after exercise onset.
METHODSDiastolic and systolic myocardial strains and twist were monitored by two-dimensional (2D) speckle-tracking echocardiography with high temporal resolution in 28 young men (mean age: 23 ± 4 years) who performed five similar constant work-load exercises on a cycloergometer (target heart rate: 125 bpm). 2D cine-loops were recorded every 15 seconds during the first minute of exercise, and then every 30 seconds for the next 3 minutes.
RESULTSDuring the first 60 seconds of exercise, SV (from 104 ± 15 to 126 ± 21 mL, p<0.001) increased concomitantly with LV strain and strain rates. Early filling was the main SV determinant during this phase, probably linked to the increase of venous return (at the very beginning of exercise), LV relaxation (from 1.5 ± 0.3 to 2.5 ± 0.4 s -1 , p<0.001) and untwisting (from -78 ± 34 to -165 ± 61 deg.s -1 , p<0.001). After the first minute, SV remained constant, while LV untwisting continued to increase (from -165 ± 61 to -187 ± 60 deg.s -1 , p<0.001) and the other systolic and diastolic parameters reached a plateau.
CONCLUSIONThis study gives new mechanical insights into LV kinetics to address the challenge of SV response at the onset of exercise.
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Transfer Learning Effects of Biofeedback Running Retraining in Untrained Conditions
Medicine & Science in Sports & Exercise. ., Post Acceptance: April 09, 2019
Abstract:
Running gait retraining via peak tibial shock biofeedback has been previously shown to reduce impact loading and mitigate running-related symptoms. In previous research, peak tibal shock is typically measured and trained for one limb at a single constant training speed during all training sessions. The goal of this study was to determine how runners transfer learning in the trained limb to the untrained limb at different unconstrained speeds.
MethodsThirteen runners (3 females, age = 41.1 ± 6.9 years, running experience = 6.8 ± 4.4 years, weekly running distance = 30.7 ± 22.2 km) underwent running gait biofeedback retraining via continuous tibial acceleration measured at the right distal tibia. Before and after the training, participants were asked to run at their self-selected constrained training speeds (2.8 ± 0.2 m·s -1 ) and at 110% and 90% of the training speed. Pre- and post-training peak tibial shock values for each limb were compared.
ResultsParticipants reduced peak tibial shock in the trained limb by 35-37% ( p <0.05, Cohen's d = 0.78-0.85), and in the untrained limb by 20-23% ( p <0.05, Cohen's d = 0.51-0.71) across the three testing speeds. The reduction was not significantly different between the trained and untrained limbs ( p = 0.31-0.79, Cohen's d = 0.18-0.45). Similarly, there was no difference in peak tibial shock reduction among the three running speeds ( p = 0.48-0.61, Cohen's d = 0.06-0.45).
ConclusionParticipants demonstrated transfer learning effects evidenced by concomitant reduced peak tibial shock in the untrained limb, and the learning effects were retrained when running at a 10% variance of the training speed.
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Effect of Shoe and Surface Stiffness on Lower Limb Tendon Strain in Jumping
Medicine & Science in Sports & Exercise. ., Post Acceptance: April 08, 2019
Abstract:
Tendinopathies are painful overuse injuries observed in athletes participating in jumping sports. These injuries are heavily dependent on the resulting strain from the applied mechanical load. Therefore, mechanisms to reduce tendon strain may represent a primary prevention strategy to reduce the incidence of tendinopathy.
PurposeThe purpose of this study was to examine the effect of shoe and surface stiffness on Achilles and patellar tendon strains during jumping. We hypothesized that less stiff shoes and surfaces would reduce Achilles and patellar tendon strains during jumping.
MethodsThirty healthy male basketball players performed countermovement jumps in three shoes and on three surfaces with different stiffness while motion capture, force platform, and jump height data were collected. Magnetic resonance imaging was used to obtain participant-specific tendon morphology, and a combined dynamometry/ultrasound/electromyography session was used to obtain tendon material properties. Finally, a musculoskeletal model was used to estimate tendon strains in each surface and shoe combination.
ResultsAchilles tendon strains during landing were reduced by 5.3% in the least stiff shoe compared to the stiffest shoe ( p = 0.021) due to differences in bending stiffness altering the center of pressure location. Furthermore, Achilles tendon strains during landing were 5.7% and 8.1% lower on the stiffest surface compared to the least stiff and middle stiffness surfaces, respectively ( p ≤ 0.047), due to changes in ground reaction force magnitude and center of pressure location. No effects of shoe stiffness or surface construction were observed for jump height ( p > 0.243) or peak patellar tendon strains ( p > 0.259).
ConclusionsChanges to shoe stiffness and surface construction can alter Achilles tendon strains without affecting jump performance in athletes.
Key Terms
Achilles tendon; patellar tendon; musculoskeletal modeling; tendinopathy; injury prevention.
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Resistance Training Induces Antiatherogenic Effects on Metabolomic Pathways
Medicine & Science in Sports & Exercise. ., Post Acceptance: April 08, 2019
Abstract:
Arising evidence suggests that resistance training has the potential to induce beneficial modulation of biomarker profile. To date, however, only immediate responses to resistance training have been investigated using high-throughput metabolomics whereas the effects of chronic resistance training on biomarker profile have not been studied in detail.
MethodsA total of 86 recreationally active healthy men without previous systematic resistance training background were allocated into i) a resistance training (RT) group (n=68, age 33 ± 7 years, body mass index (BMI) 28 ± 3 kg/m2) and ii) a non-RT group (n=18, age 31 ± 4 years, BMI 27 ± 3 kg/m2). Blood samples were collected at baseline (PRE), after 4 weeks (POST-4wk), and after 16 weeks of resistance training intervention (POST-16wk), as well as baseline and after the non-RT period (20–24 weeks). Nuclear magnetic resonance (NMR) -metabolome platform was used to determine metabolomic responses to chronic resistance training.
ResultsOverall, the resistance training intervention resulted in favorable alterations (P < 0.05) in body composition with increased levels of lean mass (~2.8 %), decreased levels of android (~9.6 %), and total fat mass (~7.5 %). These changes in body composition were accompanied by anti-atherogenic alterations in serum metabolome profile (FDR < 0.05) as reductions in non-HDL cholesterol (e.g., free cholesterol, remnant cholesterol, IDL cholesterols, LDL cholesterols) and related apolipoprotein B, and increments in conjugated linoleic fatty acids levels were observed. Individuals with the poorest baseline status (i.e. body composition, metabolome profile) benefitted the most from the resistance training intervention.
ConclusionsIn conclusion, resistance training improves cardiometabolic risk factors and serum metabolome even in previously healthy young men. Thus, suggesting attenuated risk for future cardiovascular disease.
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Diverse Exercises Similarly Reduce Older Adults' Mobility Limitations
Medicine & Science in Sports & Exercise. ., Post Acceptance: April 08, 2019
Abstract:
Little is known about the comparative effectiveness of exercise programs, especially when delivered at a high intensity, in mobility-limited older adults. We compared the effects of 25 sessions of high-intensity agility exergaming (EXE) and stationary cycling (CYC) at the same cardiovascular load on measured and perceived mobility limitations, balance, and health-related quality of life (QoL) in mobility-limited older adults.
MethodsRandomized to EXE (n=28) and CYC (n=27), mobility-impaired older adults (age 70) exercised 5x/week for 5 weeks at 80% of age-predicted maximal heart rate. Wait-listed controls did not exercise (n=28).
ResultsGroups did not differ at baseline in any outcomes (p>0.05). The primary outcomes (SF-36: EXE: 6.9%, effect size:2.2; CYC: 5.5%, 1.94; WOMAC: EXE:-27.2%, -3.83; CYC:-17.2, -2.90) improved similarly (p>0.05). Secondary outcomes, including body mass (-3.7%), depression (-18%), and walking capacity (13.5%) also improved (p<0.05) similarly after the two interventions. Activities of daily living, Berg Balance Score, BestTest scores, and dynamic gait index improved more (p<0.05) after EXE than CYC. COP of standing sway path improved in 1 of 6 tests only after EXE (p<0.05). Post-exercise cardiovascular response improved in EXE (p=0.019). CON did not change in any outcomes (p>0.05).
ConclusionsWhen matched for cardiovascular and perceived effort, two diverse high-intensity exercise programs improved health-related QoL, perceived mobility limitation, and walking capacity similarly and balance outcomes more in mobility-limited older adults, expanding these older adults' evidence-based exercise options to reduce mobility limitations.
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Serum Endocannabinoid and Mood Changes after Exercise in Major Depressive Disorder
Medicine & Science in Sports & Exercise. ., Post Acceptance: April 08, 2019
Abstract:
The endocannabinoid (eCB) system is implicated in the pathophysiology of depression and is responsive to acute exercise in healthy adults.
PurposeWe aimed to describe acute changes in serum eCBs across a prescribed moderate (MOD) and a self-selected/preferred (PREF) intensity exercise session in women with major depressive disorder (MDD) and determine relationships between changes in eCBs and mood states.
MethodsWomen with MDD (n=17) exercised in separate sessions for 20 min on a cycle ergometer at both MOD or PREF in a within-subjects design. Blood was drawn before and within 10 min after exercise. Serum concentrations of eCBs (anandamide [AEA]; 2-arachidonoylglycerol [2-AG]) and related lipids (palmitoylethanolamine [PEA]; oleoylethanolamine [OEA]; 2-oleoylglycerol [2-OG]) were quantified using stable isotope-dilution, liquid chromatography/mass spectrometry/mass spectrometry. The profile of mood states and state-trait anxiety inventory (state only) were completed prior to, 10 min and 30 min post-exercise.
ResultsSignificant elevations in AEA (p=0.013) and OEA (p=0.024) occurred for MOD (moderate effect sizes: Cohen's d=0.58 and 0.41, respectively). Significant (p<0.05) moderate negative associations existed between changes in AEA and mood states for MOD at 10 min (depression, confusion, fatigue, total mood disturbance [TMD] & state anxiety) and 30 min post-exercise (confusion, TMD & state anxiety). Significant (p<0.05) moderate negative associations existed between 2-AG and mood states at 10 min (depression & confusion) and 30 min post-exercise (confusion & TMD). Changes in eCBs or related lipids or eCB-mood relationships were not found for PREF.
ConclusionGiven the broad, moderate-strength relationships between improvements in mood states and eCB increases following MOD, it is plausible that the eCB system contributes to the mood-enhancing effects of prescribed acute exercise in MDD. Alternative mechanisms are likely involved in the positive mood state effects of preferred exercise.
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Trends in Step-determined Physical Activity among Japanese Adults from 1995 to 2016
Medicine & Science in Sports & Exercise. ., Post Acceptance: March 30, 2019
Abstract:
We tried to clarify the trends in step-determined physical activity (PA) among Japanese adults from 1995 to 2016.
MethodsRaw data from the National Health and Nutrition Surveys Japan (NHNS-J) performed between 1995 and 2016 was used, in compliance with the Statistics Act of Japan. NHNS-J was conducted annually by the Japanese government (the Ministry of Health, Labour, and Welfare) using a representative Japanese sample, with the same sampling method every year except in 2012 and 2016. A 1-day pedometer survey was conducted each year as a part of the NHNS-J, on a weekday in November specified by each individual. Because of the difference in age distribution of the samples, age-adjusted mean steps per day were calculated from 1995 to 2016 by sex. The time trends of step-determined PA levels among Japanese adults were described, and examined using Joinpoint regression.
ResultsThe highest age-adjusted mean number of steps for men was 8,235 steps per day in 2000, whereas it was 7,667 steps per day in 2015. The highest age-adjusted mean number of steps for women was 7,474 steps per day in 1998, and 6,691 steps per day in 2015. The age-adjusted step-determined PA trend showed significantly decreasing trend from 1997 to 2008 in men (Annual Percentage Change (APC) =-0.74, p < 0.001), and from 1998 to 2008 (APC = -1.30, p < 0.001) in women, by Joinpoint regression.
ConclusionThe age-adjusted step-determined PA among Japanese adults between 1995 and 2016 decreased from around 1997-1998 until around 2008, but since then the decreasing trend became unclear both in men and women. Continuous monitoring of PA trends is essential to assess the effectiveness of policies.
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Match Play–induced Changes in Landing Biomechanics with Special Focus on Fatigability
Medicine & Science in Sports & Exercise. ., Post Acceptance: March 30, 2019
Abstract:
Growing evidence exists that match-related fatigue induces biomechanical alterations that might increase lower extremity injury risk. Fatigue studies often use match simulation protocols that expose all subjects to a standardized demand (e.g. a fixed distance/time). In those studies, the induced level of fatigue depends then on subjects' fatigability. If between-subjects variability in fatigability is high, this might confound overall fatigue effects. Therefore the first aim was to investigate whether a fatigue protocol with fixed demand causes alterations in landing patterns. Secondly, we assessed the relationship between fatigability and landing patterns as we hypothesized that athletes with high fatigability would show movement patterns that involve greater injury risk.
MethodsEighteen athletes performed three different unilateral landing tasks before and after a match simulation protocol while muscle activation (vastus medialis, vastus lateralis, hamstrings medialis, hamstrings lateralis, gastrocnemius medialis, gastrocnemius lateralis, gluteus medius) and landing kinematics and kinetics of the hip, knee and ankle joint were recorded. Furthermore ratings of perceived exertion (RPE) were administered to measure fatigability. ANOVA analyses were conducted to investigate fatigue effects on landing patterns. Correlation analyses assessed the relationship between fatigability (post-fatigue RPE) and landing patterns.
ResultsThe ANOVA analyses did not show any overall post-fatigue alterations in landing patterns. However, correlation analyses showed an association between fatigability and landing patterns. Athletes who had higher RPE scores showed smaller post-fatigue knee flexion angles and smaller pre- and post-fatigue knee abduction angles across different landing tasks.
ConclusionThe fixed demand protocol did not cause overall alterations in landing patterns. When fatigability was taken into account, high fatigability was related with less optimal landing patterns.
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High-Frequency Stimulation on Skeletal Muscle Maintenance in Female Cachectic Mice
Medicine & Science in Sports & Exercise. ., Post Acceptance: March 30, 2019
Abstract:
Cancer cachexia, unintentional body weight loss due to cancer, affects patients' survival, quality of life, and the response to chemotherapy. While exercise training is a promising intervention to prevent and treat cancer cachexia, our mechanistic understanding of cachexia's effect on contraction-induced muscle adaptation has been limited to the examination of male mice. Since sex can impact muscle regeneration and the response to contraction in humans and mice, the impact of cachexia on the female response to eccentric contraction warrants further investigation.
PurposeThe purpose of this study was to determine if high frequency electric stimulation (HFES) could attenuate muscle mass loss during the progression of cancer cachexia in female tumor bearing mice.
Methods16~18-week female wild-type (WT) and ApcMin/+ (Min) mice performed either repeated bouts or a single bout of HFES (10 sets of 6 repetitions, ~ 22 minutes), which eccentrically contracts the Tibialis Anterior (TA) muscle. TA myofiber size, oxidative capacity, anabolic signaling and catabolic signaling were examined.
ResultsMin had reduced TA muscle mass and IIa and IIb fiber size compared to WT. HFES increased muscle weight and the mean cross-sectional area of type IIa and IIb fibers in WT and Min mice. HFES increased mTOR signaling, myofibrillar protein synthesis, and attenuated cachexia-induced AMPK activity. HFES attenuated the cachexia-associated decrease in skeletal muscle oxidative capacity.
ConclusionHFES in female mice can activate muscle protein synthesis through mTOR signaling and repeated bouts of contraction can attenuate cancer-induced muscle mass loss.
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Obesity Prevalence and Musculoskeletal Injury History in Probation Officers
Medicine & Science in Sports & Exercise. ., Post Acceptance: March 28, 2019
Abstract:
The purpose of the present investigation was to identify 1) the prevalence of overweight and obesity and 2) factors associated with previous work-related musculoskeletal injury, and physical activity levels in North Carolina probation officers.
METHODSNorth Carolina probation officers (n=1,866) were sent a questionnaire on demographics, work history, injury history, and physical activity. A multivariable logistic regression model estimated the odds of reporting work-related musculoskeletal injury history within the past year, and multivariable ordinal logistic regression estimated the odds of reporting lower physical activity levels in the previous month. Odds ratios (OR) with 95% confidence intervals (CI) excluding 1.00 were deemed significant.
RESULTSComplete data were available for 1,323 probation officers (70.9% completion rate; 46.5% female; mean±SD age=39.9±10.0 years). 80.8% of officers were classified as overweight and obese (body mass index [BMI]≥25kg/m 2 ), with 49.9% and 9.5% categorized as obese (BMI≥30kg/m 2 ) and severely obese (BMI≥40kg/m 2 ), respectively. Being older (1-year increase; OR=1.06; 95% CI=1.04-1.09) and severely obese (compared to normally weighted; OR=2.56; 95% CI=1.19–5.51) was associated with a greater odds of sustaining a work-related musculoskeletal injury in the past year. A higher number of years of employment (one-year increase; OR=1.03; 95% CI=1.01–1.04), being overweight or obese (compared to normal weight; OR=1.57–3.22) and being female (compared to male; OR=0.38; 95% CI=0.31–0.47) was associated with greater odds of lower physical activity levels in the previous month.
CONCLUSION
The prevalence of obesity is alarmingly high in probation officers, and is associated with a greater likelihood of sustaining previous work-related musculoskeletal injury and engaging in lower amounts of PA. Public safety administrators may consider worksite exercise/diet interventions and annual physical employment standards to combat obesity.
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Cardiopulmonary Profile of Individuals with Intellectual Disability
Medicine & Science in Sports & Exercise. ., Post Acceptance: March 28, 2019
Abstract:
Individuals with intellectual disabilities (ID) are often sedentary and have low fitness levels. Current knowledge supports the existence of physiological barriers resulting in low fitness and exercise intolerance in individuals with Down syndrome (DS), which might be applicable to other ID etiologies. If physiological barriers exist in ID, this would require adaptation of the physical activity guidelines.
PurposeThe aim of this study was to assess differences in cardiopulmonary profiles, including maximal oxygen uptake, during a cardiopulmonary exercise test (CPET) in individuals with ID without DS and healthy controls.
MethodsParticipants performed an incremental CPET on a treadmill until exhaustion. Outcomes were HRpeak, absolute VO 2 peak, relative VO 2 peak, VEpeak, VCO 2 peak, OUES, VE/VCO 2 slope, absolute O 2pulse, relative O 2 pulse, difference from predicted HRpeak, heart rate reserve, RERpeak, ventilatory threshold (VT) and VT as percentage of VO 2 peak. Differences between groups were analyzed with Student's T-tests and multiple linear regression after adjusting for potential confounders (sex, age, BMI, activity level).
ResultsIndividuals with ID had worse outcomes on all of the cardiopulmonary outcomes, except for VT expressed as percentage of VO 2 peak and VE/VCO 2 slope (p<0.05). Having ID was an independent predictor of reduced physiologic function during exercise (p<0.05).
ConclusionThese results demonstrate that individuals with ID present exercise intolerance potentially related to lower peak heart rates, impairments in ventilatory function and these results also suggest the possibility of peripheral muscle hypoperfusion. Existing physical activity guidelines likely underestimate the actual intensity of activity performed by individuals with ID and need to be adapted.
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Physiological Responses of Male and Female Race Car Drivers during Competition
Medicine & Science in Sports & Exercise. ., Post Acceptance: April 04, 2019
Abstract:
Automobile racing is one of the largest spectator sports in the world with male and female drivers competing together. Popular media has speculated on the relative capabilities of males and females in automobile racing, yet there are no scientific investigations examining physiological responses to racing among males and females.
PURPOSE(1) To evaluate the physiological responses of male and female drivers in open and closed cockpit race cars; (2) to examine the moderating influence of menstrual cycle phase on physiological responses to racing among female drivers.
METHODSHeart rate, breathing rate, skin temperature, core temperature and physiological strain index (PSI) were measured using the Equivital Life Monitor in male (n=6) and female (n=6) drivers at three races in open or closed cockpit cars. Among females, menstrual cycle phase for each race was recorded.
RESULTSDuring racing conditions there was no difference (P>0.05) between male and female drivers for heart rate, skin temperature, core temperature, or PSI. The female drivers had a higher (P<0.001) breathing rate compared to the male drivers. Compared to the follicular phase, the luteal phase had an increased (P<0.001) heart rate, breathing rate, skin temperature, core temperature, and PSI. The closed cockpit cars elicited (P<0.001) a higher skin temperature, core temperature and physiological strain index as compared to the open cockpit cars.
CONCLUSIONSThere was no differences in the physiological responses to automobile racing between male and female drivers. The luteal phase elicited higher physiological responses than the follicular phase, but was not different from the male drivers. Thereby, practitioners should focus on reducing stresses induced by a closed cockpit race car as opposed to the menstrual cycle.
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Physiological Evaluation for Endurance Exercise Prescription in Sickle Cell Disease
Medicine & Science in Sports & Exercise. ., Post Acceptance: March 25, 2019
Abstract:
While strenuous exercise may expose sickle cell disease (SCD) patients to risks of vaso-occlusive crisis (VOC), evidence suggests that regular endurance exercise may be beneficial. To test i) the safety and usefulness of a submaximal incremental exercise in evaluating physical ability of SCD patients and identify a marker for the management of endurance exercise, and ii) the feasibility of endurance exercise sessions in SCD patients.
MethodsTwenty adults with sickle cell disease (12 men and 8 women) performed a submaximal incremental exercise stopped as soon as blood lactate concentration ([lactate] b ) reached ≥ 4 mmol . L -1 and used to determine the first lactate threshold (LT1). Fifteen of those patients (8 men and 7 women) also performed three 30-min endurance exercise sessions at ~2.5 mmol . L -1 of [lactate] b on separate occasions.
ResultsLT1 occurred at 47 ± 3 and 33 ± 3 W for men and women, respectively, demonstrating the extreme deconditioning and thus low physical ability of adult SCD patients. Most of the physiological parameters associated with LT1 correlated with hemoglobin concentration. During endurance exercise, peripheral oxygen saturation and [lactate] b most often remained stable and within acceptable ranges.
ConclusionsThe proposed strategy of submaximal incremental exercise allowed safe determination of LT1, an important parameter of patients' physical ability. The study also demonstrated the feasibility and safety of individually-tailored endurance exercises at ~2.5 mmol . L -1 of [lactate] b . These latter results suggest that endurance training programs may be considered for adult SCD patients and that the method proposed here may be helpful in that regard.
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Impact of Eccentric or Concentric Training on Body Composition and Energy Expenditure
Medicine & Science in Sports & Exercise. ., Post Acceptance: March 25, 2019
Abstract:
To compare the effects of 8-week eccentric (ECC) versus concentric (CON) training using downhill and uphill running in rats on whole body composition, bone mineral density (BMD), and energy expenditure (EE).
MethodsAnimals were randomly assigned to one of the following groups: 1) control (CTRL), 2) +15% uphill-running slope (CON), 3) –15% downhill-running slope (ECC15) and 4) –30% downhill-running slope (ECC30). Those programs enabled to achieve conditions of iso-power output for CON and ECC15 and of iso-oxygen uptake (VO 2 ) for CON and ECC30. Trained rats ran 45min at 15 m⋅min -1 five times per week. Total (TBM), fat (FBM) and lean (LBM) body mass measured through EchoMRI™, and 24-hour EE including basal metabolic rate (BMR) assessed using PhenoMaster/LabMaster™ cage system were obtained before and after training. At sacrifice, the right femur was collected for bone parameters analysis.
ResultsWhile TBM increased in all groups over the 8-week period, almost no change occurred for FBM in exercised groups (CON: -4.8±6.18 g; ECC15: 0.6±3.32 g; ECC30: 2.6±6.01 g). The gain in LBM was mainly seen for ECC15 (88.9±6.85 g) and ECC30 (101.6±11.07 g). ECC was also seen to positively affect BMD. An increase in BMR from baseline was seen in exercise groups (CON: 13.9±4.13 kJ·day -1 ; ECC15: 11.6±5.10 kJ·day -1 ; ECC30: 18.3±4.33 kJ·day -1 ) but not in CTRL one. This difference disappeared when BMR was normalized for LBM.
ConclusionsResults indicate that for iso-VO 2 training, the impact on LBM and BMD is enhanced with ECC as compared to CON, and that for iso-power but lower VO 2 ECC, an important stimulus for adaptation is still observed. This provides further insights for the use of ECC in populations with cardiorespiratory exercise limitations.
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Weight Training and Risk of 10 Common Types of Cancer
Medicine & Science in Sports & Exercise. ., Post Acceptance: March 25, 2019
Abstract:
Ample data support that leisure time aerobic moderate to vigorous physical activity (MVPA) is associated with lower risk of at least seven types of cancer. However, the link between muscle-strengthening activities and cancer etiology is not well-understood. Our objective was to determine the association of weight lifting with incidence of 10 common cancer types.
MethodsWe used multivariable Cox regression to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for association of weight lifting with incidence of 10 cancer types in the NIH-AARP Diet and Health Study follow-up. Weight lifting was modeled continuously and categorically. Dose-response relationships were evaluated using cubic restricted spline models. We explored whether associations varied by subgroups defined by sex, age, and body mass index (BMI) using the Wald test for homogeneity. We examined joint categories of MVPA and weight lifting in relation to cancer risk for significant associations.
ResultsAfter adjusting for all covariates including MVPA, we observed a statistically significant lower risk of colon cancer (P trend =0.003) in individuals who weight lifted; the HR and 95% CI associated with low and high weight lifting as compared with no weight lifting were 0.75(CI:0.66,0.87) and 0.78(CI:0.61,0.98) respectively. This relationship differed between men and women (HR men =0.91 ;CI:0.84, 0.98; HR women=1.00; CI:0.93, 1.08) (P interaction =0.008). A lower risk of kidney cancer among weight lifters was observed but became non-significant after adjusting for MVPA (P trend =0.06); resulting in a HR of 0.94 (CI:0.78,1.12) for low weight lifting and 0.80 (CI:0.59,1.11) for high weight lifting.
ConclusionParticipants who engaged in weight lifting had a significantly lower risk of colon cancer and a trend towards a lower risk of kidney cancer than participants who did not weight lift. Keywords
Resistance, strengthening, epidemiology, physical activity, colon
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Blood Flow–restricted Exercise Does Not Induce a Cross-transfer of Effect: An RCT
Medicine & Science in Sports & Exercise. ., Post Acceptance: March 19, 2019
Abstract:
The goal of this trial was to determine whether low-load blood flow restricted (BFR) exercise of appendicular muscles induces a cross-transfer of effect to the trunk extensor (TE) muscles, such that low-load TE exercise would enhance TE size and function to a greater extent than standard low-load exercise in people with recurrent low back pain (LBP). We also investigated the direct effects of BFR exercise in the appendicular muscles.
Methods32 adults with recurrent, non-specific LBP were randomized into two groups: Appendicular BFR Exercise (BFR Exercise) or Control Exercise (CON Exercise). All participants trained (2x/week) for 10-weeks, with a 12-week follow-up. Participants performed three sets of leg extension (LE), plantar flexion (PF), and elbow flexion (EF) exercises followed by low-load TE exercise without BFR. Outcome measures included MRI-derived muscle size (quadriceps and TE), strength (LE, PF, EF, and TE), and endurance (LE and TE).
ResultsThere was no evidence for a cross-transfer of effect to the trunk extensors. There was also no statistically significant enhancement of limb skeletal muscle size or function of BFR relative to CON Exercise at any time point; though, moderate effect sizes for BFR exercise were observed for enhanced muscle size and strength in the leg extensors.
ConclusionsLow-load BFR exercise of the appendicular muscles did not result in a cross-transfer of effect to the TE musculature. There was also no significant benefit of low-load BFR exercise on the appendicular muscle size and function, suggesting no benefit from low-load BFR exercise in adults with recurrent, non-specific LBP.
This is an open access article distributed under the Creative Commons Attribution License 4.0 (CCBY), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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Beep Test Performance Is Influenced by 30 Minutes of Cognitive Work
Medicine & Science in Sports & Exercise. ., Post Acceptance: March 19, 2019
Abstract:
This study explored conflicting findings in the literature on the influence of perceived cognitive fatigue on physical performance by testing the effect of the Stroop task (high cognitive load) on an intermittent running test (beep test).
MethodsIn a within-subjects repeated measures experiment, 13 active athletes performed the beep test on two occasions, in a randomized, counterbalanced order. In each session a preceding cognitive task was completed for 30 minutes, with the incongruent Stroop task in the high load condition, and the congruent Stroop task in the low load condition. Perceived cognitive fatigue was measured before testing (baseline) and at 10, 20, and 30 minutes of the cognitive load manipulation. Perceived effort on the cognitive task and general motivation for the physical task (beep test) were measured prior to the beep test, and motivation-related perception of the beep test and ratings of perceived exertion were measured after completion of the test. Heart rate and beep test performance (completion stage and time) were also recorded.
ResultsThe incongruent Stroop task was perceived as more fatiguing and effortful. Participants also withdrew from the beep test significantly earlier in the high load condition ( M = 8:48 min, SD = 2:32 min) compared to the low load condition ( M = 9:20 min, SD = 2:28 min), F (1,11) = 21.76, p < .01, ŋ 2 = .67. There were no differences in heart rate or general motivation between the two conditions.
ConclusionsWhereas previous research shows that active athletes can maintain performance on the beep test after 10 minutes of the incongruent Stroop task, this study shows that performance is impaired after thirty minutes. Variables in need of exploration in future investigations include experience with both the physical and cognitive task.
This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal.
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Effect of Creatine Supplementation on the Airways of Youth Elite Soccer Players
Medicine & Science in Sports & Exercise. ., Post Acceptance: March 19, 2019
Abstract:
Introduction
Owing to its well-established ergogenic potential, creatine is a highly popular food supplement in sports. As an oral supplement, creatine is considered safe and ethical. However, no data exist on the safety of creatine on lung function in athletes. The aim of this project was to evaluate the effects of a standard course of creatine on the airways of youth elite athletes.
Methods
Nineteen elite soccer players, aged 16-21yr, completed a stratified, randomized, double-blind, placebo-controlled, parallel-group trial. The creatine group ( n =9) ingested 0.3 g/kg/d of creatine monohydrate (CM) for 1wk (loading phase) and 5 g/d for 7wk (maintenance phase), and the placebo group ( n =10) received the same dosages of maltodextrin. Airway inflammation (assessed by exhaled nitric oxide, F ENO) and airway responsiveness (to dry air hyperpnoea) were measured pre- and post-supplementation.
Results
Mild, unfavorable changes in F E NO were noticed by trend over the supplementation period in the CM group only ( P =0.056 for interaction, η 2 =0.199), with a mean group change of 9 ± 13 ppb in the CM group versus -5 ± 16 ppb in the placebo group ( P =0.056, d =0.695). Further, the maximum fall in forced expiratory volume in 1 sec (FEV 1 ) after dry air hyperpnoea was larger by trend post-supplementation in the CM group compared to the placebo group: 9.7 ± 7.5% versus 4.4 ± 1.4%, respectively ( P =0.070, d =0.975). These adverse effects were more pronounced when atopic players only ( n =15) were considered.
Conclusion
Based on the observed trends and medium-to-large effect sizes, we cannot exclude that creatine supplementation has an adverse effect on the airways of elite athletes, particularly in those with allergic sensitization. Further safety profiling of the ergogenic food supplement is warranted.
This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal.
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Microparticle Responses to Aerobic Exercise and Meal Consumption in Healthy Men
Medicine & Science in Sports & Exercise. ., Post Acceptance: March 19, 2019
Abstract:
Microparticles (MPs) are shed extracellular vesicles that express the pro-thrombotic tissue factor (TF). Aerobic exercise may reduce MP count and TF expression. This study investigated the impact of acute running or rest followed by standardised meal consumption on MP phenotypes and TF expression.
Methods15 males (age: 22.9 ± 3.3 years; body mass: 81.9 ± 11.4 kg; V[Combining Dot Above]O 2 max 54.9 ± 6.5 mL·kg·min -1 ; mean ± SD) completed 1h of running (70% V[Combining Dot Above]O 2 max) or rest at 9am, and consumed a standardised meal (1170 kcal, 43% CHO, 17% PRO, 40% fat) at 10:45am. Venous blood samples were taken at 9am, 10am and 11:30am. MP concentration, diameter, phenotypes and TF-expression were assessed using nanoparticle tracking analysis (NTA) and flow cytometry.
ResultsNTA identified no changes in MP concentration or diameter in response to time or trial. Flow cytometry revealed total MP count increased from 9am to 10am (1.62 ± 2.28 to 1.74 ± 2.61 x10 10 /L, p = .016, effect size (η 2 ) = .105), but was unaffected by trial. TF + platelet-derived MP % reduced from 9am to 10am (44.0 ± 21.2 to 21.5 ± 9.3%, p = .001, η 2 = .582) after exercise only (control: 36.8 ± 18.2 to 34.9 ± 11.9%, p = .972). TF + neutrophil-derived MP % reduced from 9am to 11:30am (42.3 ± 17.2 to 25.1 ± 14.9%, p = 0.048, η 2 = .801) in the exercise trial only (control: 28.5 ± 15.7 to 32.2 ± 9.6%, p = .508).
ConclusionRunning induced a significant reduction in %TF + platelet and neutrophil MP, suggesting a transient reduction in cardiovascular risk via reduced TF-stimulated thrombosis. This requires further investigation over longer time periods in cardiovascular disease populations.
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