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Ted Polglaze and Matthias W. Hoppe

Metabolic power ( P met ) has been proposed as a tool to estimate the energetic demands of variable-speed locomotion typically seen in team sports. 1 From the outset, it should be stated that this model is not able to fully account for the physical demands of team-sport activity, 2 , 3 but nor

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Richard Latzel, Olaf Hoos, Sebastian Stier, Sebastian Kaufmann, Volker Fresz, Dominik Reim and Ralph Beneke

in direction and speed. 8 Although the BEST had been designed for testing match-related fitness, its energetic profile is not known. Therefore, the aim of this study was to provide a first metabolic profile of the BEST in junior elite basketball players. The metabolic profile was assessed by a

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Jonathan K. Holm, Jonas Contakos, Sang-Wook Lee and John Jang

This study investigated the energetics of the human ankle during the stance phase of downhill walking with the goal of modeling ankle behavior with a passive spring and damper mechanism. Kinematic and kinetic data were collected on eight male participants while walking down a ramp with inclination varying from 0° to 8°. The ankle joint moment in the sagittal plane was calculated using inverse dynamics. Mechanical energy injected or dissipated at the ankle joint was computed by integrating the power across the duration of the stance phase. The net mechanical energy of the ankle was approximately zero for level walking and monotonically decreased (i.e., became increasingly negative) during downhill walking as the slope decreased. The indication is that the behavior of the ankle is energetically passive during downhill walking, playing a key role in dissipating energy from one step to the next. A passive mechanical model consisting of a pin joint coupled with a revolute spring and damper was fit to the ankle torque and its parameters were estimated for each downhill slope using linear regression. The passive model demonstrated good agreement with actual ankle dynamics as indicated by low root-mean-square error values. These results indicate the stance phase behavior of the human ankle during downhill walking may be effectively duplicated by a passive mechanism with appropriately selected spring and damping characteristics.

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Mhairi K. MacLean and Daniel P. Ferris

biomechanical perspective, an exoskeleton that assists at one lower limb joint but not others should alter energetic cost differently depending on the locomotor task. A large majority of the total mechanical work performed by muscles during a step can be calculated as the summation of positive and negative

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Tiago M. Barbosa, Mário Costa, Daniel A. Marinho, Joel Coelho, Marc Moreira and António J. Silva

The aim was to develop a path-flow analysis model for young swimmers’ performance based on biomechanical and energetic parameters, using structural equation modeling. Thirty-eight male young swimmers served as subjects. Performance was assessed by the 200-m freestyle event. For biomechanical assessment the stroke length, the stroke frequency and the swimming velocity were analyzed. Energetics assessment included the critical velocity, the stroke index and the propulsive efficiency. The confirmatory model explained 79% of swimming performance after deleting the stroke index-performance path, which was nonsignificant (SRMR = 0.06). As a conclusion, the model is appropriate to explain performance in young swimmers.

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Elisa S. Arch and Bretta L. Fylstra

The large, late-stance energy generated by the ankle is believed to be critical during gait. However, the distal foot absorbs/dissipates a considerable amount of energy during the same phase. Thus, the energy generated by the combined ankle–foot system is more modest, which raises questions regarding the necessity of such a large ankle power and the interplay between foot and ankle energetics. This study aimed to evaluate our conservation of energy hypothesis, which predicted if distal foot energy absorption/dissipation was reduced, then less energy would be generated at the ankle and thus the same combined ankle–foot energetics would be achieved. Motion analysis data were collected as healthy subjects walked under 2 conditions (Shoes, Footplate). In the Footplate condition, the shoe was replaced with a customized, rigid footplate with a rocker profile. In support of the hypothesis, there was significantly less positive ankle and less negative distal foot work with footplate use, resulting in very similar combined ankle–foot work between conditions. These findings suggest that there is an interplay between the energy generated by the ankle and absorbed by the foot. This interplay should be considered when designing orthotic and prosthetic ankle–foot systems and rehabilitation programs for individuals with weakened ankle muscles.

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Anthony S. Kulas, Thomas C. Windley and Randy J. Schmitz

Context:

Functional implications of clinically relevant abdominal postures have been sparsely examined.

Objectives:

To evaluate the reliability of sustaining abdominal postures during single-leg landings and the effects of abdominal postures on lower extremity kinetics and energetics.

Design:

One-way ANOVA tested effects of leg-spring stiffness and lower extremity energetics across groups (control, abdominal hollowing [AH], and pelvic tilting [PT]).

Participants:

12 male (24.0 ± 3.4 years) and 12 female (21.9 ± 2.3 years) healthy, recreationally active subjects.

Main Outcome Measures:

Leg-spring stiffness and relative joint-energy absorption from control, AH, and PT groups.

Results:

AH and PT ICCs2,k and standard error of measurements (AH = 0.53 ± 0.4 cm, PT = 0.9° ± 0.8°) were moderate to high. Relative knee-energy-absorption effect sizes comparing the control and treatment groups revealed moderate treatment effects (AH = 0.66%, PT = 0.41%).

Conclusions:

Abdominal postures can be reliably performed during a single-leg-landing task. Energy-absorption effect sizes suggest a link between the trunk and lower extremity.

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Pedro Figueiredo, Ana Silva, António Sampaio, João Paulo Vilas-Boas and Ricardo J. Fernandes

The aim of this study was to evaluate the determinants of front crawl sprint performance of young swimmers using a cluster analysis. 103 swimmers, aged 11- to 13-years old, performed 25-m front crawl swimming at 50-m pace, recorded by two underwater cameras. Swimmers analysis included biomechanics, energetics, coordinative, and anthropometric characteristics. The organization of subjects in meaningful clusters, originated three groups (1.52 ± 0.16, 1.47 ± 0.17 and 1.40 ± 0.15 m/s, for Clusters 1, 2 and 3, respectively) with differences in velocity between Cluster 1 and 2 compared with Cluster 3 (p = .003). Anthropometric variables were the most determinants for clusters solution. Stroke length and stroke index were also considered relevant. In addition, differences between Cluster 1 and the others were also found for critical velocity, stroke rate and intracycle velocity variation (p < .05). It can be concluded that anthropometrics, technique and energetics (swimming efficiency) are determinant domains to young swimmers sprint performance.

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Steven T. McCaw, Jacob K. Gardner, Lindsay N. Stafford and Michael R. Torry

An inverse dynamic analysis and subsequent calculation of joint kinetic and energetic measures is widely used to study the mechanics of the lower extremity. Filtering the kinematic and kinetic data input to the inverse dynamics equations affects the calculated joint moment of force (JMF). Our purpose was to compare selected integral values of sagittal plane ankle, knee, and hip joint kinetics and energetics when filtered and unfiltered GRF data are input to inverse dynamics calculations. Six healthy, active, injury-free university student (5 female, 1 male) volunteers performed 10 two-legged landings. JMFs were calculated after two methods of data filtering. Unfiltered: marker data were filtered at 10 Hz, GRF data unfiltered. Filtered: both GRF and marker data filtered at 10 Hz. The filtering of the GRF data affected the shape of the knee and hip joint moment-time curves, and the ankle, knee and hip joint mechanical power-time curves. We concluded that although the contributions of individual joints to the support moment and to total energy absorption were not affected, the attenuation of high-frequency oscillations in both JMF and JMP time curves will influence interpretation of CNS strategies during landing.

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Philip Davis, Renate M. Leithäuser and Ralph Beneke

The energy expenditure of amateur boxing is unknown.

Purpose:

Total metabolic cost (Wtot) as an aggregate of aerobic (Waer), anaerobic lactic (W[lactate]), and anaerobic alactic (WPCr) energy of a 3 × 2-min semicontact amateur boxing bout was analyzed.

Methods:

Ten boxers (mean ± SD [lower/upper 95% confidence intervals]) age 23.7 ± 4.1 (20.8/26.6) y, height 180.2 ± 7.0 (175.2/185.2) cm, body mass 70.6 ± 5.7 (66.5/74.7) kg performed a semicontact bout against handheld pads created from previously analyzed video footage of competitive bouts. Net metabolic energy was calculated using respiratory gases and blood [lactate].

Results:

Waer, 526.0 ± 57.1 (485.1/566.9) kJ, was higher (P < .001) than WPCr, 58.1 ± 13.6 (48.4/67.8) kJ. W[lactate], 26.2 ± 7.1 (21.1/31.3) kJ, was lower (P < .001) than Waer and WPCr. An ~70-kJ fraction of the aerobic energy expenditure reflects rephosphorylation of high-energy phosphates during the breaks between rounds, which elevated Wtot to ~680 kJ with relative contributions of 77% Waer, 19% WPCr, and 4% W[lactate].

Conclusions:

The results indicate that the metabolic profile of amateur boxing is predominantly aerobic. They also highlight the importance of a highly developed aerobic capacity as a prerequisite of a high activity rate during rounds and recovery of the high-energy phosphate system during breaks as interrelated requirements of successful boxing.