The effects of a 12-week jump rope exercise program on body composition, insulin sensitivity, and academic self-efficacy in obese adolescent girls.

Background Childhood obesity is strongly associated with the development of cardiovascular disease (CVD). Exercise interventions have been used for obese children and adolescents to prevent the manifestation of CVD risks, such as hypertension and insulin resistance (IR). Additionally, obesity has been shown to be linked to low self-efficacy in adolescents, which has been shown to negatively impact academic performance. Therefore, the purpose of this study was to examine the effects of a 12-week jump rope exercise program on body composition, CVD risk factors, and academic self-efficacy (ASE) in obese adolescent girls with prehypertension. Methods Adolescent girls with prehypertension and obesity (n = 48, age 14-16 years) were randomly assigned to either the jump rope exercise group (EX, n = 24) or the control group (CON, n = 24). Body composition, blood pressure (BP), blood glucose, insulin levels, homeostatic model assessment of insulin resistance (HOMA-IR) (marker of IR), and ASE were assessed before and after 12 weeks of exercise training or control. Results There were significant group × time interactions following the 12-week exercise program for body fat percent, waist circumference (WC), systolic blood pressure (SBP), blood glucose, insulin levels, and HOMA-IR, which were all significantly reduced (p < 0.05). A significant improvement (p <0.05) was observed in task difficulty preference (TDP) and self-regulatory efficacy (SRE) following exercise training. Additionally, ASE was strongly correlated (r = -0.58) with body composition. Conclusions This study provides evidence that jump rope exercise intervention can be a useful therapeutic treatment to improve CVD risk factors and ASE in obese adolescent girls with prehypertension.

Acoustic remote sensing for source localization and atmospheric tomography: Applications of the cross-correlation Green's function retrieval method.

In this work, the application of the cross-correlation Green's function retrieval method for source localization and atmospheric acoustic tomography is presented. Open field experimental measurements of an acoustic source, with an impulsive waveform, are conducted for the evaluation of an array system. Of particular interest are the source localization and sound speed estimation capabilities of the array system. The cross-correlation delay-and-sum beamformer is used to estimate source directivity and sound speed. This beamformer inherently employs the cross-correlation Green's function retrieval method between a pair of receivers. The beamforming results adequately identify the various source directions as well as the scatterers along the propagation path. Reasonable sound speed estimates are obtained at the peak frequency of the retrieved Green's functions. In the case of atmospheric acoustic tomography, the estimated sound speed from the array system can serve as an average background sound speed in a tomographic inversion algorithm. Utilizing a tomographic inversion algorithm with radial basis functions and the estimated sound speed, the reconstruction of temperature and wind velocity profiles are demonstrated.

Green's function extraction by crosscorrelation and multidimensional deconvolution for outdoor sound propagation.

In this work, the Green's function is estimated from outdoor measurements of controlled-sources. Crosscorrelation and multidimensional deconvolution have successfully been employed for Green's function retrieval. Crosscorrelation assumes a lossless medium and equipartitioned wavefield; when these assumptions are not satisfied it may result in a Green's function smeared with the source point-spread function. Multidimensional deconvolution removes the point-spread function from the retrieved Green's function. Both methods are employed to estimate the Green's function between two array stations for a single and multiple controlled-sources. The results demonstrate that the source-to-center radius has a negligible effect on the retrieved Green's function, if the source-to-center radius is larger than the distance between the two array stations.

Concurrent Validity of Wearable Activity Trackers Under Free-Living Conditions.

Brooke, SM, An, H-S, Kang, S-K, Noble, JM, Berg, KE, and Lee, J-M. Concurrent validity of wearable activity trackers under free-living conditions. J Strength Cond Res 31(4): 1097-1106, 2017-The purpose of this study is to evaluate the concurrent validity of wearable activity trackers in energy expenditure (EE) and sleep period time (SPT) under free-living conditions. Ninety-five (28.5 ± 9.8 years) healthy men (n = 34) and women (n = 61) participated in this study. The total EE and SPT were measured using 8 monitors: Nike+ FuelBand SE (NFB), Garmin VivoFit (VF), Misfit Shine (MF), Fitbit Flex (FF), Jawbone UP (JU), Polar Loop (PL), Fitbit Charge HR (FC), and SenseWear Armband Mini (SWA) (criterion measures: SWA for EE and a sleep log for SPT). The mean absolute percent error (MAPE) for EE was 13.0, 15.2, 15.5, 16.1, 16.2, 22.8, and 24.5% for PL, MF, FF, NFB, FC, JU, and VF, respectively. Mean absolute percent errors were calculated for SPT to be 4.0, 8.8, 10.2, 11.5, 12.9, 13.6, 17.5, and 21.61% for VF, FF, JU, FC, MF, SWA laying down, PL, and SWA, respectively. Concurrent validity was examined using equivalence testing on EE (equivalence zone: 2,889.7-3,531.9 kcal); 2 trackers fell short of falling in the zone: PL (2,714.4-3,164.8 kcal) and FC (2,473.8-3,066.5 kcal). For SPT (equivalence zone: 420.6-514.0 minutes), several monitors fell in the zone: PL (448.3-485.6 minutes), MS (442.8-492.2 minutes), and FF (427.7-486.7 minutes). This study suggests that the PL and FC provide a reasonable estimate of EE under free-living conditions. The PL, FC, and MF were the most valid monitors used for measuring SPT.

How accurate are the wrist-based heart rate monitors during walking and running activities? Are they accurate enough?

BACKGROUND: Heart rate (HR) monitors are valuable devices for fitness-orientated individuals. There has been a vast influx of optical sensing blood flow monitors claiming to provide accurate HR during physical activities. These monitors are worn on the arm and wrist to detect HR with photoplethysmography (PPG) techniques. Little is known about the validity of these wearable activity trackers. AIM: Validate the Scosche Rhythm (SR), Mio Alpha (MA), Fitbit Charge HR (FH), Basis Peak (BP), Microsoft Band (MB), and TomTom Runner Cardio (TT) wireless HR monitors. METHODS: 50 volunteers (males: n=32, age 19-43 years; females: n=18, age 19-38 years) participated. All monitors were worn simultaneously in a randomised configuration. The Polar RS400 HR chest strap was the criterion measure. A treadmill protocol of one 30 min bout of continuous walking and running at 3.2, 4.8, 6.4, 8.0, and 9.6 km/h (5 min at each protocol speed) with HR manually recorded every minute was completed. RESULTS: For group comparisons, the mean absolute percentage error values were: 3.3%, 3.6%, 4.0%, 4.6%, 4.8% and 6.2% for TT, BP, RH, MA, MB and FH, respectively. Pearson product-moment correlation coefficient (r) was observed: r=0.959 (TT), r=0.956 (MB), r=0.954 (BP), r=0.933 (FH), r=0.930 (RH) and r=0.929 (MA). Results from 95% equivalency testing showed monitors were found to be equivalent to those of the criterion HR (±10% equivalence zone: 98.15-119.96). CONCLUSIONS: The results demonstrate that the wearable activity trackers provide an accurate measurement of HR during walking and running activities.

The effect of cadence on cycling efficiency and local tissue oxygenation.

The purpose of this study was to compare 3 cycling cadences in efficiency/economy, local tissue oxygen saturation, heart rate, blood lactate, and global and local rating of perceived exertion (RPE). Subjects were 14 trained cyclists/triathletes (mean age 30.1 ± 5.3 years; VO(2) peak 60.2 ± 5.0 ml·kg(-1)·min(-1)) who performed three 8-minute cadence trials (60, 80, and 100 rpm) at 75% of previously measured peak power. Oxygen consumption and respiratory exchange ratio were used to calculate efficiency and economy. Results indicated that both efficiency and economy were higher at the lower cadences. Tissue oxygen saturation was greater at 80 rpm than at 60 or 100 rpm at minute 4, but at minute 8, tissue oxygen saturation at 80 rpm (57 ± 9%) was higher than 100 rpm (54 ± 9%, p = 0.017) but not at 60 rpm (55 ± 11%, p = 0.255). Heart rate and lactate significantly increased from minute 4 and minute 8 (p < 0.05) of submaximal cycling. Local RPE at 80 rpm was lower than at 60 or 100 rpm (p < 0.05). It was concluded that (a) Trained cyclists and triathletes are more efficient and economical when cycling at 60 rpm than 80 or 100 rpm. (b); Local tissue oxygen saturation levels are higher at 80 rpm than 60 and 100 rpm; (c). Heart rate and blood lactate levels are higher with cadences of 80 and 100 than 60 rpm; and (d). Local and global RPE is lower when cycling at 80 rpm than at 60 rpm and 100 rpm. A practical application of these findings is that a cadence of 60 rpm may be advantageous for performance in moderately trained athletes in contrast to higher cadences currently popular among elite cyclists.

The effects of shoe traction and obstacle height on lower extremity coordination dynamics during walking.

This study aims to investigate the effects of shoe traction and obstacle height on lower extremity relative phase dynamics (analysis of intralimb coordination) during walking to better understand the mechanisms employed to avoid slippage following obstacle clearance. Ten participants walked at a self-selected pace during eight conditions: four obstacle heights (0%, 10%, 20%, and 40% of limb length) while wearing two pairs of shoes (low and high traction). A coordination analysis was used and phasing relationships between lower extremity segments were examined. The results demonstrated that significant behavioral changes were elicited under varied obstacle heights and frictional conditions. Both decreasing shoe traction and increasing obstacle height resulted in a more in-phase relationship between the interacting lower limb segments. The higher the obstacle and the lower the shoe traction, the more unstable the system became. These changes in phasing relationship and variability are indicators of alterations in coordinative behavior, which if pushed further may have lead to falling.

Sound propagation in the vicinity of an isolated building: an experimental investigation.

Recently, the study of acoustics in urban terrain has been concerned with the propagation of sound through street canyons typical of residential areas in large cities, while sparsely built suburban and rural areas have received little attention. An isolated building's effect on propagating sound is a fundamental case of suburban acoustics and urban acoustics in general. Its study is a necessity in order to determine the processes that might be required to model the sound field in the building's vicinity, e.g., diffraction and wind effects. The work herein presents the results of an experimental effort to characterize the interaction between propagating sound and a single story, gabled-roof building typical of some North American suburban and rural areas. Recorded data are found to reasonably compare to a common diffraction model in some instances.

Relationship between measures of body size and composition and velocity of lactate threshold.

The purpose of this investigation was to explore the relationship between velocity of lactate threshold (vLT) and various measures of body mass and composition: mass, lean mass, fat mass, percent body fat (% fat), and body surface area (BSA). We hypothesized that mass would be inversely related to vLT, and that differences in measures of body mass and composition would account for a significant amount of variability in vLT. A total of 21 healthy male runners served as subjects. Body composition was assessed by hydrostatic weighing. A significant negative relationship (r = -0.759, p < or = 0.01) was between body mass and vLT. The coefficient of determination between vLT and body mass indicated that nearly 58% of the variability in vLT was explained by body mass in these subjects. Significant relationships were also between vLT and BSA (r = -0.72, p < or = 0.01), fat mass (r = -0.70, p < or = 0.01), % fat (r = -0.59, p < or = 0.01), and lean mass (r = -0.41, p < or = 0.05). Linear regression yielded the following model: y = 369.48 - 1.7343 (X), where y = predicted vLT (m.min(-1)) and X = body mass (kilograms) (SEE = 15.45). Velocity of lactate threshold was significantly inversely related with body mass in a group of male runners. The calculated coefficient of determination suggests that nearly 58% of the variability in vLT was explained by body mass. The present data suggest consideration of categorizing participants in 'road runs' by body mass to equate competition, as is done in other sports (e.g., weightlifting).

Comparison of physical and performance characteristics of NCAA Division I football players: 1987 and 2000.

The purpose of this study was to compare normative data from present Division I National Collegiate Athletic Association football teams to those from 1987. Players were divided into 8 positions for comparisons: quarterbacks (QB), running backs (RB), receivers (WR), tight ends (TE), offensive linemen (OL), defensive linemen (DL), linebackers (LB), and defensive backs (DB). Comparisons included height, body mass, bench press and squat strength, vertical jump, vertical jump power, 40-yd-dash speed, and body composition. Independent t-tests were used to analyze the data with level of significance set at p < 0.01. Significant differences (p < 0.01) were found in 50 of 88 comparisons. From 1987 until 2000, Division I college football players in general have become bigger, stronger, faster, and more powerful. Further research is warranted to investigate if these trends will continue.

Physical Activity Participation: Social Cognitive Theory versus the Theories of Reasoned Action and Planned Behavior.

Social cognitive theory and the theories of reasoned action and planned behavior were examined in the prediction of 4 weeks of physical activity participation. The theories of reasoned action and planned behavior were supported. Attitude and perceived control predicted intention, and intention predicted physical activity participation. The social cognitive theory variables significantly predicted physical activity participation, with self-efficacy and self-evaluation of the behavior significantly contributing to the prediction. The greater the confidence in participating in physical activity and the greater the satisfaction with present physical activity, the more physical activity performed. Hierarchical regression analyses indicated that perceived control and intentions did not account for any unique variation in physical activity participation over self-efficacy. Therefore the social cognitive theory constructs were better predictors of physical activity than those from the theories of reasoned action and planned behavior.