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Changes in Energy Cost and Total External Work of Muscles in Elite Race Walkers Walking at Different Speeds

100%
Chwała W., Klimek A., Mirek W.
Journal of Human Kinetics
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2014
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vol. 44
|
issue 1
129-136
EN
The aim of the study was to assess energy cost and total external work (total energy) depending on the speed of race walking. Another objective was to determine the contribution of external work to total energy cost of walking at technical, threshold and racing speed in elite competitive race walkers. The study involved 12 competitive race walkers aged [...] years with 6 to 20 years of experience, who achieved a national or international sports level. Their aerobic endurance was determined by means of a direct method involving an incremental exercise test on the treadmill. The participants performed three tests walking each time with one of the three speeds according to the same protocol: an 8-minute walk with at steady speed was followed by a recovery phase until the oxygen debt was repaid. To measure exercise energy cost, an indirect method based on the volume of oxygen uptake was employed. The gait of the participants was recorded using the 3D Vicon opto-electronic motion capture system. Values of changes in potential energy and total kinetic energy in a gate cycle were determined based on vertical displacements of the centre of mass. Changes in mechanical energy amounted to the value of total external work of muscles needed to accelerate and lift the centre of mass during a normalised gait cycle. The values of average energy cost and of total external work standardised to body mass and distance covered calculated for technical speed, threshold and racing speeds turned out to be statistically significant [...] . The total energy cost ranged from 51.2 kJ.m-1 during walking at technical speed to 78.3 kJ.m-1 during walking at a racing speed. Regardless of the type of speed, the total external work of muscles accounted for around 25% of total energy cost in race walking. Total external work mainly increased because of changes in the resultant kinetic energy of the centre of mass movement.
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Muscle Torque and its Relation to Technique, Tactics, Sports Level and Age Group in Judo Contestants

100%
Lech G., Chwała W., Ambroży T., Sterkowicz S.
Journal of Human Kinetics
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2015
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vol. 45
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issue 1
167-175
EN
The aim of this study was to perform a comparative analysis of maximal muscle torques at individual stages of development of athletes and to determine the relationship between muscle torques, fighting methods and the level of sports performance. The activity of 25 judo contestants during judo combats and the effectiveness of actions were evaluated. Maximum muscle torques in flexors/extensors of the body trunk, shoulder, elbow, hip and knee joints were measured. The level of significance was set at p≤0.05; for multiple comparisons the Mann-Whitney U test, p≤0.016, was used. Intergroup differences in relative torques in five muscle groups studied (elbow extensors, shoulder flexors, knee flexors, knee extensors, hip flexors) were not significant. In cadets, relative maximum muscle torques in hip extensors correlated with the activity index (Spearman's r=0.756). In juniors, maximum relative torques in elbow flexors and knee flexors correlated with the activity index (r=0.73 and r=0.76, respectively). The effectiveness of actions correlated with relative maximum torque in elbow extensors (r=0.67). In seniors, the relative maximum muscle torque in shoulder flexors correlated with the activity index during the second part of the combat (r=0.821).
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Assessment of the strength and endurance of the trunk muscle in patients with low back pain

88%
Głodzik J., Chwała W., Marchewka A., Ruchlewicz T., Skura A.
Medical Rehabilitation
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2008
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vol. 12(3)
15-23
EN
Introduction: In this study, strength and endurance of the trunk muscles were assessed in patients with spondyloarthrosis of the lower spine. Material and methods: 52 women and 49 men with low back pain syndrome (LBPS) were enrolled into the study. The muscle strength of the flexors and extensors of the trunk was determined by calculation of the maximum (MT) and relative torque (RT) during an isometric contraction. Evaluation of endurance of the extensors used calculation of the regression coefficient of the strength reduction during the testing of maximum strength capability. The obtained results were compared to results obtained in healthy persons. Moreover, the relation of those parameters to age, body-mass index – BMI (describing somatic habitus) and the Oswestry Disability Index – ODI (describing pain intensity during activities of daily living) was assessed. Separate analyses were conducted for the groups of males and females.Results: Based on the conducted study and the performed analyses, it can be stated that in patients with chronic low back pain syndrome there is a marked reduction in trunk muscle strength as compared to healthy persons. For females, the reduction ranged from 45% (flexors) to 48% (extensors) for absolute maximum torque values, while for relative values (RT) – from 51% (flexors) to 56% (extensors). In men, the strength reduction of abdominal and back muscles was smaller and was approximately 40% (for MT and RT). Because of such differences in the strength of the back muscles and methodological reasons, endurance variables were not compared. Reduction in trunk muscle strength is primarily due to the pain syndrome and does not depend on patients’ age or habitus. Lower muscle strength can affect the intensity of spinal pain during every-day activities.Conclusions: Precise determination of strength and endurance of the trunk muscles and the appropriate selection of methods of their reinforcement should constitute one of the principal aims of rehabilitation treatment in patients with low back pain.
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