Relationship between abdominal adiposity,cardiovascular fitness,and biomarkers of cardiovascular risk in British adolescents

BackgroundPuberty is a critical time in the development of overweight and obesity. The aim of this study was to examine relationships between measures of adiposity, cardiovascular fitness, and biomarkers of cardiovascular disease risk in adolescents.MethodsIn a cross-sectional study design, 129 girls and 95 boys aged 12.9–14.4 years at various stages of puberty were included, along with their mothers (n = 217) and fathers (n = 207). Anthropometric assessments of adiposity were made, along with cardiovascular physical fitness, using the 20-m shuttle run test, and biomarkers associated with cardiovascular risk, including glucose, insulin, triglyceride, fibrinogen, and C-reactive protein (CRP) concentrations.ResultsWaist-to-height ratio values were similar in boys and girls and correlated positively with diastolic blood pressure, insulin, triglyceride, fibrinogen, and CRP concentrations, and inversely with cardiovascular fitness scores. Skinfold thickness measurements were higher in girls. High-molecular-weight adiponectin concentrations were lower in boys than girls, particularly in late puberty, and CRP levels were higher. Cardiovascular fitness, maternal body mass index (BMI), and paternal BMI contributed independently to the variance in waist measurements in girls and boys. Gender, triceps skinfold thickness, and weight-to-height ratio, but not parental BMI, contributed independently to the variance in cardiovascular fitness.ConclusionThere is a relationship between measures of adolescent adiposity and parental weight that involves factors other than cardiovascular fitness. Adolescent boys have relatively more abdominal fat than girls and a tendency to have a proinflammatory profile of biomarkers. These observations suggest that family and social environmental interventions are best undertaken earlier in childhood, particularly among boys.     

Body Composition and Anthropometric Correlates of Isokinetic Leg Extension Strength of Young Adult Males

Abstract

The present study examined the relative importance of body size and composition as determinants of individual differences in isokinetic leg extensor strength in young adult males performing at slow, moderate, and fast speeds. The subjects were 31 males between the ages of 19 and 29 years, who were not participating in weight training programs. Low to moderate correlations were found between isokinetic strength and body size or body composition measurements. At each speed, similar proportions of the variance in peak torque values were accounted for by lean body weight (23-30%) and thigh volume (20-37%). However, body weight, often suggested as the best reference standard for equalizing strength scores, also accounted for only 13-24% of the variance in peak torque values at each of the speeds tested. The moderate correlations reported in this study do not support the use of body size and composition measurements as a means of adjusting strength values.     

Anthropometrics and electromyography as predictors for maximal voluntary isometric arm strength

BackgroundMuscular strength can be conceptually determined by two components: muscle activation and size. Muscle activation by the central nervous system can be measured by surface electromyography (sEMG). Muscular size reflects the amount of contractile protein within a skeletal muscle and can be estimated by anthropometric measurements. The purpose of this study was to determine the relative contributions of size parameters and muscle activation to the prediction of maximal voluntary isometric elbow flexion strength.MethodsA series of anthropometric measurements were taken from 96 participants. Torque and root-mean-square (RMS) of the sEMG from the biceps brachii were averaged across three maximal voluntary isometric contractions. A multiple linear regression analysis was performed based on a Pearson's correlation matrix.ResultsBody weight (BW) accounted for 39.1% and 27.3% in males and females, respectively, and was the strongest predictor of strength for males. Forearm length (L3) was the strongest predictor of strength in females (partial R² = 0.391). Elbow circumference (ELB) accounted for a significant (p < 0.05) amount of variance in males but not females. The addition of sEMG RMS as a third variable accounted for an average of 10.1% of the variance excluding the equation of BW and L3 in females. The strongest prediction equation included BW, L3, and ELB accounting for 55.6% and 58.5% of the variance in males and females, respectively.ConclusionAnthropometrics provide a strong prediction equation for the estimation of isometric elbow flexion strength. Muscle activation, as measured by sEMG activity, accounted for a significant (p < 0.05) amount of variance in most prediction equations, however, its contribution was comparable to an additional anthropometric variable.     

Endurance tests are the most reliable core stability related measurements

PurposeTo determine the intra-tester reliability of clinical measurements that assess five components related to core stability: strength, endurance, flexibility, motor control, and function.MethodsParticipants were 15 college-aged males who had not suffered any orthopedic injury in the past year. Core strength measurements included eight isometric tests and a sit-up test. The four core endurance tests were the trunk flexor test, trunk extensor test, and bilateral side bridge tests. Flexibility tests included the sit-and-reach test and active range of the trunk and hip joint motions. Proprioception via passive reposition tests of the hips and a single limb balance test on an unsteady platform were used to evaluate core motor control. Functional measurements consisted of a squat test and a single leg hop test for time and distance. Measurements were performed during two data collection sessions with a week's rest between the sessions. Intra-class correlation coefficients were calculated to establish reliability.ResultsThe overall intra-rater reliability for all core stability related measurements ranged from low (ICC = 0.35, left hip reposition) to very high (ICC = 0.98, sit-and-reach). As a group, the core endurance tests were observed to be the most reliable.ConclusionThere are highly reliable tests in each of the five groups. Overall, core endurance tests are the most reliable measurements, followed by the flexibility, strength, neuromuscular control, and functional tests, respectively.     

A Comparative Study of Physique and Performance Measures Resulting from a Short-Term Physical Fitness Course

Abstract

Cardiorespiratory and anthropometric assessments were made on 95 randomly selected young college males enrolled in three physical fitness sections and one tennis course, each lasting eight weeks. Laboratory and field measures were utilized to report and evaluate changes in functional fitness and physique variables, including nine selected fat and girth measurements, height and weight, timed vital capacity, Harvard Step Test, grip strength, mile run time, and vertical jump. Analysis of the data yielded the following conclusions: (a) Eight weeks of physical fitness training can produce significant improvements in physique and circulorespiratory characteristics; (b) A skill-oriented tennis class demonstrates no significant physical improvements; (c) Body weight can be increased while body fat is lost; (d) Vital capacity has little value in reflecting levels of physical performance; (e) Specificity of a physical fitness program will influence its outcome.     

A Comparison of Physical Fitness Ratings as Determined by the Pulse-Ratio Test and Rogers' Test of Physical Fitness

Abstract

This experiment was undertaken to determine the effects of a six-week progressive weight training program on the development of strength and muscle hypertrophy, using one exercise, the deep-knee bend, with varying repetitions. Thirty students were chosen by random from beginning weight lifting classes at Michigan State University. Following a two-week conditioning period the subjects were divided into three groups of ten each for the controlled training period. The programs were as follows: Group A—3 sets of 9-10 repetitions, Group B—3 sets of 5-6 repetitions, and Group C—3 sets of 2-3 repetitions. Individuals in each group handled maximum weight loads for the number of repetitions each was required to perform. The effectiveness of the program was determined by three measurements: (a) thigh girth, (b) dynamic strength as measured by one RM on the deep-knee bend, and (c) static strength as measured on the dynamometer. The results were graphically analyzed and percentages calculated. The data were also statistically-treated using analysis of covariance. No significant differences were found between the three systems of training. All training procedures resulted in the improvement of static and dynamic strength.     

Age,Height, Weight,and Grip Strength

Abstract

This study recorded the age, height, weight, and grip strength of 299 healthy adult males, representing college students newly enrolled in a body conditioning class, college athletes, recruit policemen and policemen. Analysis of the data showed that for men in condition and within the limits of the study, grip strength is significantly related to weight but not to height or age.     

Cardiovascular Measurements on College-Age Smokers and Non-Smokers

Abstract

Thirty-six male college students were measured in six cardiovascular factors as recorded by the Cameron Heartometer. Seventeen of these subjects were smokers and 19 were non-smokers. The purpose of this investigation was to find what residual, as opposed to acute, effects, smoking has on young men. Each subject in both groups was measured in six cardiovascular factors, nine times successively, during his testing period. The smokers abstained from smoking on the day of testing.

The residual effects of smoking in young men, if there be any, cannot be demonstrated in a statistically significant manner in certain cardiovascular factor measurements in the quiet state.     

The relationships between step count and all-cause mortality and cardiovascular events: A dose–response meta-analysis

BackgroundA goal of 10,000 steps per day is widely advocated, but there is little evidence to support that goal. Our purpose was to examine the dose–response relationships between step count and all-cause mortality and cardiovascular disease risk.MethodsCochrane Central Register of Controlled Trials, EMBASE, OVID, PubMed, Scopus, and Web of Science databases were systematically searched for studies published before July 9, 2021, that evaluated the association between daily steps and at least 1 outcome.ResultsSixteen publications (12 related to all-cause mortality, 5 related to cardiovascular disease; and 1 article contained 2 outcomes: both all-cause death and cardiovascular events) were eligible for inclusion in the meta-analysis. There was evidence of a nonlinear dose–response relationship between step count and risk of all-cause mortality or cardiovascular disease (p = 0.002 and p = 0.014 for nonlinearity, respectively). When we restricted the analyses to accelerometer-based studies, the third quartile had a 40.36% lower risk of all-cause mortality and a 35.05% lower risk of cardiovascular event than the first quartile (all-cause mortality: Q1 = 4183 steps/day, Q3 = 8959 steps/day; cardiovascular event: Q1 = 3500 steps/day, Q3 = 9500 steps/day; respectively).ConclusionOur meta-analysis suggests inverse associations between higher step count and risk of premature death and cardiovascular events in middle-aged and older adults, with nonlinear dose–response patterns.     

Effects of Aerobic Dance on Physical Work Capacity,Cardiovascular Function and Body Composition of Middle-Aged Women

Abstract

The purpose of this study was to determine the effects of aerobic dance on physical work capacity, cardiovascular function and body composition of young middle-aged women. Maximal oxygen uptake ([Vdot]O ₂ max), heart rate during submaximal treadmill walking, resting heart rate and blood pressure, and body composition were determined before and after a 10-week aerobic dance conditioning program in 28 women (18 experimental and 10 control), aged 25 to 44 years. During the 10-week treatment period, the experimental subjects participated in 45 min of aerobic dance at 70–85% of the heart rate reserve, 3 days · week ^–1,whereas the control group did not participate in any regular strenuous physical activity. Changes in the experimental group were significantly greater than in the control group for [Vdot]O ₂ max expressed in 1 · min ^–1 or relative to body weight or fat-free weight (5 to 7% vs. – 5 to – 8%), time on a continuous grade-incremented walking treadmill test (16% vs. 1%), heart rate during submaximal stages of the treadmill test (– 9% vs. 1%) and resting heart rate (– 8% vs. 2%). Resting systolic and diastolic blood pressure; body weight; percent fat, fat weight, and fat-free weight estimated using underwater weighing; sum of seven skinfolds; and sum of seven circumferences did not change significantly in either group. It was concluded that aerobic dance performed 30–45 min, 3 days · week ^–1 for 10 weeks significantly improves physical work capacity and cardiovascular function, but without dietary control, does not alter body composition in sedentary middle-aged women.     

A Cluster Analysis of Static Strength Tests

Abstract

Ages, heights, weights, and 24 static (cable tensiometer) strength test scores were obtained from 81 college men enrolled in service course classes at the University of Oregon during the 1963–64 academic year. Of the 276 intercorrelations between strength scores, 215 were significant (p > .01; r ≥ .285). In general, when age, height, and weight were held constant, the intercorrelations between the strength scores from the different segments of the body were not greatly changed from those of the zero-order correlations between the same strength scores. Five functional clusters or groupings of strength were isolated and identified by means of the application of cluster analysis to the intercorrelations between the strength tests and by an analysis of muscle actions involved in the performance of each of the strength tests. The findings in this study disclosed five clusters or groupings of strength which were specific to shoulder, trunk, neck, wrist, and hip joints. They could also be described as arm and forearm strength, trunk strength, neck strength, hand strength, and thigh and leg strength.     

Construction of a Muscular Strength Test for Boys in Grades 4, 5, and 6

Abstract

In this study, a strength test for boys 9 through 12 years of age in grades 4, 5, and 6 was constructed based upon cable tension strength tests. From 18 cable tension strength tests, the following four were selected by multiple correlation procedures: shoulder extension, trunk extension, knee extension, and ankle plantar flexion (ankle extension). The total of these four tests was designated the strength composite. Norms were prepared based on age and weight, utilizing Roger's method in the construction of Strength Index norms; the subjects were 826 boys from ten communities located in various parts of Oregon. A strength quotient was derived by dividing the achieved by the norm strength composite and multiplying by 100.     

Bases of Norms for Cable-Tension Strength Tests for Upper Elementary,Junior High,and Senior High School Girls

Abstract

Twelve anthropometric measures and 23 derived indexes were obtained from 72 girls at each level along with 25 cable tensiometer strength tests which were averaged as the criterion. The measures, indexes, and strength criterion were intercorrelated. The highest multiple correlations with the strength criterion were .822, using height times the cube root of weight and arm girth/thigh girth at the elementary level; .784, using chest girth times standing height and shoulder width at the junior high level; and .607, using arm girth and shoulder width/hip width at the senior high level. Combining all levels gave an r of .844 using age and weight. Anthropometric measures intercorrelated higher for elementary school girls, but the indexes intercorrelated higher at the junior and senior high levels than at the elementary level.     

Performance Differences between National Football League and High School American Football Combine Participants

Purpose: The purpose of this study was to determine magnitudes of differences for anthropometric and athletic performance scores between high school and elite college-level American football players. Method: Participants included high school-age (n = 3,666) athletes who participated in American football combines, as well as elite college-level (n = 5,537) athletes who participated in the National Football League (NFL) scouting combine. Combine data included position; height; weight; 10-, 20-, and 40-yard dash; pro-agility (PA); L-cone drill (LC); vertical jump (VJ); and broad jump (BJ). Athletes were separated into their respective position group, defensive back (DB), wide receiver (WR), linebacker (LB), quarterback (QB), running back (RB), tight end (TE), defensive line (DL), and offensive line (OL) for analysis of performance differences. Percent differences for each dependent variable were calculated to quantify magnitudes of differences. Results: NFL combine participants scored 3% to 25% better on all measurements, with the largest differences between weight and VJ (14%–25%). Conclusion: The largest measurement-specific differences between high school-age and elite college-level American football players were body size and power. Although it may seem intuitive that elite college-level players would perform better, these data provide a unique perspective to high school players, parents, and coaches, giving new information to use when designing measurement-specific athletic development programs. Thus, strength and conditioning professionals may benefit from emphasizing increases in muscle mass and power output in strength and conditioning programs.     

Altered multi-muscle coordination patterns in habitual forefoot runners during a prolonged,exhaustive run

Abstract

Introduction: In response to fatigue during an exhaustive treadmill run, forefoot runner’s muscles must adapt to maintain their pace. From a neuromuscular control perspective, certain muscles may not be able to sustain the force to meet the run’s demands; thus, there may be alternative muscle coordination in the lower extremity that allows for continued running for an extended period of time. The aim of this study was to quantify the change in muscle coordination during a prolonged run in forefoot runners.

Methods: Thirteen forefoot runners performed exhaustive treadmill runs (mean duration: 15.4?±?2.2?min). The muscle coordination of seven lower extremity muscles was quantified using a high-resolution time–frequency analysis together with a pattern recognition algorithm.

Results: The mean EMG intensity for the lateral and medial gastrocnemius muscles decreased with the run (p?=?0.02; 0.06). The weight factors of the second principal pattern decrease by 128.01% by the end of run (p?=?0.05, Cohen’s d?=?0.42) representing a relatively greater biceps femoris activation in midstance but smaller midstance rectus femoris, vastus medialis, triceps surae, and tibialis anterior activation.

Discussion: These results suggest that forefoot runners cannot sustain plantar flexor activation throughout an exhaustive run and change their muscle coordination strategy as a compensation. Understanding the underlying compensation mechanisms humans use to cope with fatigue will help to inform training modalities to enhance these late stage muscle activation strategies for athletes with the goal of improving performance and reducing injury.     

Physical Characteristic,Perceptual-Motor,and Intelligence Differences between Third- and Sixth-Grade Children

Abstract

The following measures were recorded for third- and sixth-grade children: height; weight; grip strength of the dominant and nondominant hands; elbow flexion and elbow extension strength; hip flexion and hip extension strength; dynamic balance; ball-throwing accuracy; speed of hand-arm movement; eye-hand coordination; stimulus discrimination and hand speed; perceptual ability; academic achievement; and intelligence. It was concluded that sixth-grade boys had, in general, the most favorable recorded measures, followed by sixth-grade girls, third-grade boys, and third-grade girls, these differences usually being significant.     

Comments: Rebuttal to above Comments on “Visual Movements of Batters”

Abstract

The research was undertaken to determine if an increase in the duration of a sustained voluntary isometric contraction is more closely related to changes in cardiovascular endurance or changes in strength. Subjects (N = 24) were tested before and after a training program to determine their endurance (oxygen consumption) and strength. The training program consisted of one daily sustained voluntary isometric contraction of the left forearm flexors at a prescribed percentage of the subject's maximum isometric strength. When the mean duration of contractions for each group showed a significant increase, training ceased.

The groups which trained with contractions of 50, 75, and 100 percent of a maximum voluntary contraction showed significant increases in strength, but not in endurance. The group which trained with a 25 percent contraction increased significantly in endurance, but not in strength. The increased duration of contractions at percentages greater than or equal to 50 percent of a maximum voluntary contraction appeared to be due to increased strength. Hence, measuring cardiovascular endurance by the duration of a sustained voluntary isometric contraction at percentages greater than 25 percent seems unjustified.     

Association between knee-to-hip flexion ratio during single-leg vertical landings,and strength and range of motion in professional soccer players

Abstract

The aim of this study was to test the correlation between knee-to-hip flexion ratio during a single leg landing task and hip and knee strength, and ankle range of motion. Twenty-four male participants from a professional soccer team performed a continuous single leg jump-landing test during 10s, while lower limb kinematics data were collected using a motion analysis system. After biomechanical testing, maximal isometric hip (abduction, extension, external rotation), knee extension and flexion strength were measured. Maximum ankle dorsiflexion range of motion was assessed statically using the weight bearing lunge test. Pearson correlation coefficients were calculated to determine the associations between the predictor variables (knee and hip strength, and ankle ROM) and the main outcome measure (knee-to-hip flexion ratio). Correlation between knee-to-hip flexion ratio and hip abductors strength was significant (r = ?0.47; p = 0.019). No other significant correlations were observed among the variables (p > 0.05). These results demonstrated that a lower hip abductors strength in male soccer players was correlated with a high knee-to-hip flexion ratio during landing from a single leg jump, potentially increasing knee overload by decreasing energy absorption at the hip. The results provide a novel proposal for the functioning of hip muscles to control knee overload.     

The British Olympic Association's Position Statement on Athlete Confidentiality

Abstract

In this study, we determined the specificity of a low frequency taekwondo training programme on physical fitness levels in adolescent females who receive limited physical education instruction (i.e. 2 days per week). Major components of physical fitness assessed were: skeletal muscle fitness (hand grip strength, bent arm hang, standing long jump, and isokinetic strength), flexibility (sit-and-reach test), speed and agility (10 × 5-m shuttle run), and cardiovascular fitness ([Vdot]O _2max and 20-m shuttle run). Changes in body composition were also assessed (dual X-ray absorptiometry, DXA). Participants were divided into two groups, a taekwondo training group (n = 21), which trained 50 min a day, 2 days per week for 12 weeks, and a control group (n = 10). Taekwondo training improved isokinetic strength, standing long jump, and sit-and-reach performance. Body fat mass and percent body fat were reduced. No changes in grip strength, bent arm hang time, speed and agility, or cardiorespiratory fitness were observed. Results indicate that low frequency taekwondo training in adolescent females produces beneficial changes in skeletal muscle fitness, flexibility, and body composition in a relatively short period of time. Consequently, this specific type of training can be useful to female adolescents in structured school environments where physical education classes are limited and there is little free time for physical activity.     

The relationships between step count and all-cause mortality and cardiovascular events: A dose–response meta-analysis

BackgroundA goal of 10,000 steps per day is widely advocated, but there is little evidence to support that goal. Our purpose was to examine the dose–response relationships between step count and all-cause mortality and cardiovascular disease risk.MethodsCochrane Central Register of Controlled Trials, EMBASE, OVID, PubMed, Scopus, and Web of Science databases were systematically searched for studies published before July 9, 2021, that evaluated the association between daily steps and at least 1 outcome.ResultsSixteen publications (12 related to all-cause mortality, 5 related to cardiovascular disease; and 1 article contained 2 outcomes: both all-cause death and cardiovascular events) were eligible for inclusion in the meta-analysis. There was evidence of a nonlinear dose–response relationship between step count and risk of all-cause mortality or cardiovascular disease (p = 0.002 and p = 0.014 for nonlinearity, respectively). When we restricted the analyses to accelerometer-based studies, the third quartile had a 40.36% lower risk of all-cause mortality and a 35.05% lower risk of cardiovascular event than the first quartile (all-cause mortality: Q1 = 4183 steps/day, Q3 = 8959 steps/day; cardiovascular event: Q1 = 3500 steps/day, Q3 = 9500 steps/day; respectively).ConclusionOur meta-analysis suggests inverse associations between higher step count and risk of premature death and cardiovascular events in middle-aged and older adults, with nonlinear dose–response patterns.