The Quantification of Muscle Activation During the Loaded Carry Movement Pattern.

The 'loaded carry' is a popular resistance training activity that activates core musculature across multiple movement planes while the body is in locomotion. 'Hold' exercises are similar to carry exercises but lack the locomotive aspect. Both carry and hold exercises can be completed bilaterally (farmer's carry (FC) and hold (FH)) or unilaterally (suitcase carry (SC) and hold (SH)). A deeper understanding of muscle activation between the FC and SC and intensity-matched FH and SH might improve their application. Healthy, college-aged individuals were recruited and surface electromyography of the rectus abdominis (RA), external oblique (EO), longissimus (LT), and multifidus (MF) was measured bilaterally using standard procedures. Participants completed time- and intensity-matched randomized sets of the plank, FC, SC, FH, and SH separated by 5-minute rests. A one-way ANOVA was utilized to compare exercises. The FC/FH load averaged 50.7±1.9 kg, where it was used across equally weighted dumbbells. The FC elicited higher activation bilaterally in the LT, MF, RA, and EO, compared to the FH. The SC/SH single-dumbbell load averaged 25.3±0.95 kg. There was greater activation bilaterally in the LT and MF during the SC compared to the SH. However, on the ipsilateral side of the SC, the RA and EO displayed greater activation compared to the SH, but this was not different on the contralateral side. The FC and SC were characterized by increased core muscle activation bilaterally, with the SC exhibiting unique additions to ipsilateral muscle activation.

The Impact of the Cold Pressor Test on Inter-arm Differences in Blood Pressure.

A large inter-arm difference (IAD+; ≥10mmHg between arms at rest) in blood pressure (BP) at rest is linked to cardiovascular risk, and exercise can change this difference. As mechanisms for IAD are elusive, unique physiological stimuli may provide insight towards a better understanding of this phenomenon. The cold pressor test (CPT) has a potent effect on BP and acts primarily through sympathetic nervous system (SNS) stimulation, though the effects of SNS stimulation on IAD are unknown. Therefore, the purpose of the present study was to examine the effects of the CPT on IAD. BP was monitored simultaneously using two automated, auscultatory monitors (SunTech Tango) and a non-invasive hemodynamic device (Physioflow). Participants completed a CPT test, including a 15-minute rest, three pre-test BP measurements (averaged), and a three-minute water immersion (3°C; measurements at 30-sec and 2-min). Descriptive statistics were calculated, and a repeated measures ANOVA test used to compare both the absolute and relative IAD responses. The CPT induced an average absolute increase in IAD of 4.0 mmHg at 30-sec and 6.7mmHg at 2-min across all participants (P<0.05). Differences in both the absolute and relative IAD responses to the CPT were noted between IAD- and IAD+ individuals (P<0.05). Despite a consistent HR response to the CPT between groups, stroke volume was lower in IAD+ participants at 30-sec and 2-min. Sympathetic stimulation via the CPT induced changes in both the inter-arm difference in blood pressure and hemodynamics in young, apparently-healthy individuals.

A Comparison of Muscle Recruitment Across Three Straight-Legged, Hinge-Pattern Resistance Training Exercises.

Hinge exercises are critical to building a balanced resistance training program in concert with 'knee-dominant' (e.g., squat, lunge) exercises. Biomechanical differences between various straight-legged hinge (SLH) exercises may alter muscle activation. For example, a Romanian deadlift (RDL) is a closed-chain SLH, while a reverse hyperextension (RH) is open-chain. Likewise, the RDL offers resistance via gravity while the cable pull-through (CP) offers redirected-resistance through a pulley. A deeper understanding of the potential impact of these biomechanical differences between these exercises may improve their application to specific goals. Participants completed repetition-maximum (RM) testing on the RDL, RH, and CP. On a follow-up visit, surface electromyography of the longissimus, multifidus, gluteus maximus, semitendinosus, and biceps femoris, muscles that contribute to lumbar/hip extension, was recorded. After a warm-up, participants completed maximal voluntary isometric contractions (MVICs) in each muscle. They then completed five repetitions of the RDL, RH, and CP at 50% of estimated one RM. Testing order was randomized. A one-way, repeated-measures ANOVA test was used in each muscle to compare activation (%MVIC) across the three exercises. Shifting from a gravity-(RDL) to a redirected-resistance (CP) SLH significantly decreased activation in the longissimus (-11.0%), multifidus (-14.1%), biceps femoris (-13.1%), and semitendinosus (-6.8%). Alternately, changing from a closed-(RDL) to an open-chain (RH) SLH significantly increased activation in the gluteus maximus (+19.5%), biceps femoris (+27.9%), and semitendinosus (+18.2). Alterations in the execution of a SLH can change muscle activation in lumbar/hip extensors.

Magnitude and significance of interarm blood pressure differences in children and adolescents.

BACKGROUND: An interarm difference (IAD) in blood pressure (BP) of 10 mmHg or more is a potential cardiovascular risk factor in adults, given its association with cardiovascular events/mortality. In children and adolescents, accurate BP assessment is critical for identifying risk of end organ damage. However, IAD has not been systematically studied in paediatric patients; if present and of significant magnitude, measuring BP in only one arm could lead to misclassification of hypertensive status. METHOD: In 95 children/adolescents with a normal aorta (including 15 with a history of tetralogy of Fallot) aged 7-18 years attending the Royal Children's Hospital, Melbourne, we aimed to determine the magnitude of IAD, frequency of IAD of at least 10 mmHg, difference in BP classification between arms, and influence of repeat measures on IAD in a single visit. After 5 min rest, simultaneous bilateral BP was measured in triplicate with an automated device. RESULTS: Absolute systolic IAD was 5.0 mmHg (median, interquartile range 2-8 mmHg) and was 10 mmHg or more in 14%, with no change on repeat measures. In patients with a history of aortic surgery, IAD of 10 mmHg or more occurred in 27% (transposition of the great arteries, n = 15) and 75% (aortic coarctation, n = 8). Differences in BP classification, based on initial left vs. right arm measures, occurred in 25% (normal aorta) and 40%/63% (aortic surgery), or 17% and 33%/50%, respectively if second and third measurements were averaged. CONCLUSION: Substantial interarm BP differences were common, even in apparently healthy children and adolescents: evaluation of IAD may, therefore, be important for BP classification in the paediatric setting.

Sex differences in the association between PTSD symptoms with cardiac autonomic function and subclinical atherosclerotic risk.

BACKGROUND: Post-traumatic stress disorder (PTSD) is a public health concern that may elevate the risk for cardiovascular disease (CVD). There are established sex differences in both PTSD risk and CVD risk. PURPOSE: To examine sex-specific associations between subclinical PTSD symptom severity and subclinical CVD risk in young men and women. METHODS: A total of 61 young adults (women: n = 29, mean age: 26 ± 7 years) completed the post-traumatic stress disorder civilian checklist (PCL) and the Center for Epidemiologic Studies Depression Scale (CES-D). Aortic stiffness was measured as carotid-femoral pulse wave velocity (cfPWV). Peripheral vasomotor function was measured as flow-mediated slowing (FMS) of carotid-radial PWV following 5-min forearm occlusion. Heart rate variability was used to assess sympathovagal balance as LF/HF ratio. RESULTS: PCL score was positively correlated with CES-D score (r = 0.79, p < .001), cfPWV (r = 0.33, p = .03) and LF/HF ratio (r = 0.42, p = .009) in men. PCL score was positively correlated to CES-D score (r = 0.80, p < .001) in women, but was inversely correlated to cfPWV (r = -0.38, p = .02) and LF/HF ratio (r = -0.34, p = .04). PCL score was also inversely associated with FMS in women (r = -0.49, p = .01). CONCLUSION: There are sex differences in the association of PTSD symptoms and subclinical atherosclerosis. In men, increased PTSD symptoms may increase CVD risk by increasing sympathovagal balance and aortic stiffness. In women, increased PTSD symptoms may increase CVD risk via reducing vasomotor function.

Characterization of resting and exercise inter-arm differences in SBP to isometric handgrip exercise in males and females.

A large inter-arm difference (IAD; ≥10 mmHg) in SBP is linked to cardiovascular and peripheral vascular disease, hypertension, and premature mortality. Exercise-induced IAD (eIAD) is related to resting IAD, and acute aerobic activity alters eIAD and reduces IAD in recovery. Isometric handgrip exercise (IHE) affects blood pressure (BP), though the eIAD response to IHE is unknown. Further, the eIAD response may differ between males and females. OBJECTIVES: To characterize the eIAD response to IHE in males and females. METHODS: On visit 1, participants (16 females and 15 males, aged 18-35 years) completed three maximal voluntary isometric contractions (MVIC) per arm. On visit 2, before IHE, a series of three simultaneous, bilateral BP measures were averaged at rest. During IHE, participants maintained handgrip at 20% of MVIC for 2 minutes (arm randomly assigned), at which time bilateral BP was measured (IHE) during exercise and subsequent recovery (REC1 and REC2). Repeated-measures analysis of variance assessed eIAD and SBP (time × sex). RESULTS: IHE increased absolute eIAD (4 mmHg). Differences in relative eIAD were observed at IHE and REC2 based on resting IAD status (P < 0.05). Females only had an exaggerated SBP and pulse pressure response in the working arm. CONCLUSION: Acute IHE was shown to augment eIAD. Further eIAD and resting IAD were related. Acute IHE induced different bilateral responses between males and females, though the impact of sex on eIAD warrants further investigation. Future studies should address the effects of repeated bouts of IHE, which may benefit individuals with a large resting IAD.

Fat-Free Mass and the Balance Error Scoring System Predict an Appropriate Maximal Load in the Unilateral Farmer's Walk.

This study quantified and compared unilateral farmer's walk (UFW) performance in recreationally active males and females, and determined if additional variables allowed for the prediction of a maximal safe load. Anthropometric (height, body weight (BW), body mass index, body fat percentage, fat-free mass (FFM), and fat mass), muscular endurance (maximal duration side bridge), and balance (Balance Error Scoring System (BESS)) tests were completed. Participants performed a series of 20 s UFW trials (non-dominant side) at a cadence of 66 beats/min. The initial load was 10% of BW and increased by 10% per trial until deviations in spinal alignment or compromised gait patterns were noted, and the series was terminated. The highest load carried before technical failure was recorded. Descriptive and comparative statistics and a stepwise linear regression analysis were utilized to determine relationships between UFW performance and anthropometric, muscular endurance, and balance tests. Males (N = 25) were significantly taller (177.3 ± 6.7 vs. 164.7 ± 7.2 cm, p < 0.05), heavier (81.7 ± 7.0 vs. 62.0 ± 9.4 kg, p < 0.05), and leaner (14.4 ± 4.4 vs. 22.4 ± 4.8%, p < 0.05) than females (N = 26). Further, males had a higher amount of FFM (p < 0.05) than females. The males (52.2 ± 9.0, 64% BW) carried a higher average UFW load than the females (32.5 ± 7.1 kg, 53% BW, p < 0.05). FFM was strongly predictive of UFW load (load = -9.88876 + 0.88679 × (FFM); r² = 0.774, p < 0.0001). The addition of the BESS test further increased the accuracy of the prediction equation (r² = 0.800, p < 0.0001). There are differences in UFW performance ability between males and females. As our method does not account for all potential confounding variables, the use of these equations should be combined with technique analysis and participant feedback to ensure an appropriate workload.

Stability of Resistance Training Implement alters EMG Activity during the Overhead Press.

Kettlebells often replace dumbbells during common resistance training exercises such as the overhead press. When performing an overhead press, the center of mass of a dumbbell is in line with the glenohumeral joint. In comparison, the center of mass of the kettlebell is posterior to the glenohumeral joint. Posterior displacement of the kettlebell center of mass may result in less stability during the pressing motion. The purpose of this study was to examine muscle activity during an overhead press with resistance training implements of differing stability. Surface electromyography (EMG) for the anterior deltoid and pectoralis major was analyzed for 21 subjects. Technique and pace of the overhead press were standardized and monitored. Filtered EMG data were collected, normalized, and average peak amplitude as a percentage of MVIC was calculated for each repetition. A repeated-measures analysis of variance was used to compare EMG values for the anterior deltoid and pectoralis major across implements. A statistically significant increase in normalized EMG activity (p < .05) was identified in the anterior deltoid when using the dumbbell (63.3±13.3%) compared to the kettlebell (57.9±15.0%). In this study, EMG activity was augmented in the anterior deltoid when using the more stable implement, the dumbbell.

An acute bout of aerobic exercise alters interarm systolic blood pressure difference.

BACKGROUND: Clinically, when a difference of at least 10 mmHg in systolic blood pressure (SBP) between arms exists, it is identified as an interarm systolic blood pressure difference (ISBPD). At rest, ISBPD is linked with hypertension, peripheral vascular disease, and increased premature mortality. Exercise may reveal underlying cardiovascular pathologies otherwise absent at rest. However, there have been no investigations to examine the effect of exercise on ISBPD. AIM: The aim of this investigation was to determine whether exercise may alter ISBPD when detected at rest or reveal ISBPD when it was not observed in the resting condition. METHODS: An experienced investigator sequentially measured SBP using standard auscultation in each arm (alternating order) in 85 normotensive individuals (22±6 years, 39 male, 46 female). ISBPD was quantified before exercise (PRE). Participants then completed a three-stage protocol on a cycle ergometer. A cadence of 50 rpm was maintained at a workload of 3 (EX-3; light) and 6 (EX-6; moderate) METS and during an active recovery (REC). At each stage, SBP was measured upon achieving steady-state heart rate. A logistic regression analysis was used to determine the change in odds ratio of ISBPD when exposed to exercise. RESULTS: Thirteen percent (n=11) of patients presented with ISBPD during PRE and the degree of ISBPD was lower (3.81 mmHg; P<0.05) in REC than PRE. In individuals who did not present with ISBPD during PRE (n=74), progression from EX-3 to EX-6 significantly increased the odds of developing ISBPD (4.31; P<0.05). CONCLUSION: In individuals with ISBPD at PRE, active recovery from exercise attenuated the difference between interarm SBP. Moderate-intensity exercise resulted in ISBPD not otherwise present at rest.

Eight Weeks of Kettlebell Swing Training Does not Improve Sprint Performance in Recreationally Active Females.

The kettlebell swing (KBS), emphasizing cyclical, explosive hip extension in the horizontal plane, aligns with movement- and velocity-specificity of sprinting. The present study examined the effect of an eight-week KBS intervention on sprinting in recreationally-active females, in comparison to an eight-week intervention using the stiff-legged deadlift (SDL). Following a pre-testing session measuring 30 meter sprint and countermovement vertical jump performance, participants were divided evenly by sprint time into KBS (n=8) and SDL (n=10) cohorts. Following familiarization with the exercises, KBS met twice weekly to perform swings using the Tabata interval (20s work, 10s rest, 8 rounds), stressing a rapid, explosive tempo. In contrast, the SDL group performed their Tabata stiff-legged deadlifts at a conventional resistance training tempo (2 seconds concentric, 2 seconds eccentric). Following eight weeks and greater than 95% training adherence, the SDL group only had a slightly greater average training volume (~3%) than KBS. No significant differences in pre-test values, or changes were noted in sprint performance from pre- to post-intervention in either group. An improvement in vertical jump performance was noted across groups. Potential explanations for the lack of sprint improvement compared to previous studies include differences between recreationally-active and athletic females, and low exercise volume (~46% of a comparable study with improvements in vertical jump). Future studies should seek to determine the appropriate volume and intensity for KBS components of sprint programming.

Effect of an acute bout of aerobic exercise on chemerin levels in obese adults.

AIMS: Serum chemerin concentrations are elevated in obese individuals and may play a role in type 2 diabetes. Exercise improves insulin sensitivity, which may be related to changes in chemerin. This study explored how an acute bout of aerobic exercise affected chemerin levels in non-diabetic obese adults. METHODS: Blood samples from 11 obese adults were obtained during two separate conditions: sedentary (SED) and exercise (EX; 60-65% VO2peak). Samples were drawn at baseline, immediately following exercise and hourly for an additional 2h. ANOVA was used to test for differences in chemerin between conditions. RESULTS: Unadjusted analysis showed no difference in overall change (baseline to 2h post) in chemerin between conditions. During the 2-h post-exercise period, chemerin decreased to 12% below baseline, compared to a 2.5% increase above baseline during that time period on the sedentary day (p=0.06, difference in post-to-2h change between conditions). Controlling for homeostatic model assessment of insulin resistance (HOMA-IR), a significant difference existed between EX and SED in the change in chemerin from baseline to 2-h post (p=0.02). Stratified analyses showed a consistent exercise-induced decrease in chemerin among non-insulin resistant subjects, while chemerin increased during exercise among insulin resistant subjects, and then decreased post-exercise. CONCLUSION: An acute bout of exercise in obese individuals may elicit a drop in chemerin levels during the post-exercise period, and this response may vary based on insulin resistance.

Developing best practices teaching procedures for skinfold assessment: observational examination using the Think Aloud method.

Skinfold assessment is valid and economical; however, it has a steep learning curve, and many programs only include one exposure to the technique. Increasing the number of exposures to skinfold assessment within an undergraduate curriculum would likely increase skill proficiency. The present study combined observational and Think Aloud methodologies to quantify procedural and cognitive characteristics of skinfold assessment. It was hypothesized that 1) increased curricular exposure to skinfold assessment would improve proficiency and 2) the combination of an observational and Think Aloud analysis would provide quantifiable areas of emphasis for instructing skinfold assessment. Seventy-five undergraduates with varied curricular exposure performed a seven-site skinfold assessment on a test subject while expressing their thoughts aloud. A trained practitioner recorded procedural observations, with transcripts generated from audio recordings to capture cognitive information. Skinfold measurements were compared with a criterion value, and bias scores were generated. Participants whose total bias fell within ±3.5% of the criterion value were proficient, with the remainder nonproficient. An independent-samples t-test was used to compare procedural and cognitive observations across experience and proficiency groups. Additional curricular exposure improved performance of skinfold assessment in areas such as the measurement of specific sites (e.g., chest, abdomen, and thigh) and procedural (e.g., landmark identification) and cognitive skills (e.g., complete site explanation). Furthermore, the Think Aloud method is a valuable tool for determining curricular strengths and weaknesses with skinfold assessment and as a pedagogical tool for individual instruction and feedback in the classroom.

Cardiovascular and Metabolic Demads of the Kettlebell Swing using Tabata Interval versus a Traditional Resistance Protocol.

Tabata (TAB) training, consisting of eight cycles of 20 seconds of maximal exercise followed by 10 seconds of rest, is time-efficient, with aerobic and anaerobic benefit. This study investigated the cardiovascular and metabolic demands of a TAB versus traditional (TRAD) resistance protocol with the kettlebell swing. Fourteen young (18-25y), non-obese (BMI 25.7±0.8 kg/m2) participants reported on three occasions. All testing incorporated measurements of HR, oxygen consumption, and blood lactate accumulation. Each participant completed Tabata kettlebell swings (male- 8kg, female- 4.5kg; 8 intervals; 20s maximal repetitions, 10s rest). On a subsequent visit (TRAD), the total swings from the TAB protocol were evenly divided into 4 sets, with 90s rest between sets. Outcome measures were compared using paired t-tests. The TAB was completed more quickly than the TRAD protocol (240.0±0.0 v. 521.5±3.3 sec, P<0.01), at a higher perceived exertion (Borg RPE; 15.1±0.7 v. 11.7±0.9, P<0.01). The TAB elicited a higher average VO2 value (33.1±1.5 v. 27.2±1.6 ml/kg/min, P<0.01), percent of VO2peak achieved (71.0±0.3 v. 58.4±0.3%, P<0.01), maximal HR (162.4±4.6 v. 145.6±4.8 bpm, P<0.01), and post-exercise blood lactate concentration (6.4±1.1 v. 3.7±0.5 mmol/L, P<0.01). CONCLUSION: The kettlebell swing demonstrated significantly greater cardiovascular and metabolic responses within a TAB vs. TRAD framework. Appropriate screening and risk stratification are advised before implementing kettlebell swings.

Quantifying accurate calorie estimation using the "think aloud" method.

OBJECTIVE: Clients often have limited time in a nutrition education setting. An improved understanding of the strategies used to accurately estimate calories may help to identify areas of focused instruction to improve nutrition knowledge. METHODS: A "Think Aloud" exercise was recorded during the estimation of calories in a standard dinner meal (415 kcal) in 15 nutrition-trained and 15 untrained subjects. Accuracy of participant estimation was assessed, and estimation strategies were compared in accurate vs inaccurate estimators. RESULTS: Accurate participants were more likely to demonstrate an ability to convert between common portion size measurements and serving sizes, possess some knowledge of energy density, and properly implement basic math skills. CONCLUSIONS AND IMPLICATIONS: The "Think Aloud" methodology was informative in assessing the cognitive processes behind a nutrition exercise, and further use is warranted. Focused instruction in portion size conversion, energy density, and the use of math skills may enhance calorie estimation accuracy.

Do overweight and obese individuals select a "moderate intensity" workload when asked to do so?

The purpose of this study was (1) to determine if overweight/obese individuals (age 26-50 y) would self-select moderate exercise intensity when asked to do so and (2) to determine how this self-selected workload compared to exercising at a workload (60% peak aerobic capacity) that is known to provide cardioprotective health benefits. Oxygen consumption (VO(2)) and energy expenditure were measured in 33 men/women (BMI ≥ 27 kg/m(2)) who completed two 30 min walking bouts: (1) self-selected walking pace on an indoor track and (2) prescribed exercise pace (60% VO(2) peak) on a treadmill. The data revealed that (1) the prescribed intensity was 6% higher than the self-selected pace and elicited a higher energy expenditure (P < 0.05) than the self-selected pace (+83 kJ); (2) overweight subjects walked at a slightly lower percentage of VO(2) peak than the obese subjects (P < 0.05); (3) men walked at a lower percentage of VO(2) peak than the women (P < 0.05). In conclusion when asked to walk at a moderate intensity, overweight/obese individuals tended to select a lower workload in the "moderate intensity" range which could be maintained for 30 min; however, a higher intensity which would be more cardioprotective could not be maintained for 30 min by most individuals.