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• Analysis of ground reaction force in gait during different phases of pregnancy

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  Analysis of ground reaction force in gait during different phases of pregnancy

  Author(s)

  Marta Gimunová, Mario Kasović, Martin Zvonař, Pavel Turčínek, Branka Matković, Pavel Ventruba, Martin Vaváček and Damir Knjaz

  Date

  2015-12-01

  Source

  Kinesiology 47(2015)2:236-241

  Abstract:
  During pregnancy there are increased biomechanical demands on women affecting gait parameters.
  The purpose of this study was to analyze changes in vertical ground reaction force (GRF), normalized by
  body mass, during advancing phases of pregnancy. Nine pregnant subjects participated in this study at three
  pregnancy stages. To determine in-shoe pressure distribution Pedar Insole System was used (100 Hz). Analysis
  was done on 200 steps cycles of treadmill walking at the velocity of 0.83 m·s-1. To compare the differences of
  GRFs in maximal weight acceptance, middle stance and push-off phase and time to reach these forces among
  three pregnancy stages, repeated-measures ANOVA was performed to obtain partial eta-squared values to
  measure the effect size (η>.10). To interpret the overall mean differences between the three pregnancy stages
  Cohen’s d was applied (d>.20). Altered gait pattern during advancing phases of pregnancy demonstrated in
  the current study by a significant decrease in force of maximal weight acceptance and an increase in main
  time variables of the step is suggested to be a protective mechanism against overloading the contact area of
  the foot despite the increase in body mass.
  Key words: gait, ground reaction force, pregnancy, treadmill walking

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• Effect of high-speed treadmill training with a body weight support system in a sport acceleration program with female soccer players

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  Effect of high-speed treadmill training with a body weight support system in a sport acceleration program with female soccer players

  Author(s)

  Johnson AW, Eastman CS, Feland JB, Mitchell UH, Mortensen BB, Eggett D.

  Date

  2013-06-27

  Source

  Journal of Strength and Conditional Research

  Abstract

  Maximum running speed and acceleration are essential components in many sports. The identification of specific training protocols to maximize sprint speed would be useful knowledge for coaches and players. The purpose of this study was to determine the effect of a high-speed treadmill (HST) with the use of a body weight support (BWS) system in a 6-week sport acceleration program (SAP) on female soccer athlete’s 40-yard sprint time and maximal isometric knee flexor and extensor strength. Two treatment groups and one control group were created. Both treatment groups participated in a 12-session SAP. The first treatment group (n = 12) used a BWS system while running on a HST; the second group (n = 12) used a standard treadmill (ST) with no BWS system. The participants of the control group (n = 8), NT, did not participate in a sports acceleration program and did not alter their exercise routines outside of the study. An analysis of covariance was performed using baseline measures as the covariate. The 40-yard sprint times for both treatment groups were shown to improve significantly compared with the control group (p < 0.001). Isometric knee flexor strength showed a greater increase in the ST group (p = 0.026) than in the other 2 groups, whereas knee extensor strengths did not show significant differences between treatment groups and control group (p > 0.05). Participants in the ST group had a much higher rate (66%) of shin splints and foot pain throughout the study than those in the HST (8%) and NT (0%) groups. These results can help high school coaches and athletes determine the optimal treadmill training regime.

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• Increased FXYD1 and PGC‐1α mRNA after blood flow‐restricted running is related to fibre type‐specific AMPK signalling and oxidative stress in human muscle

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  Increased FXYD1 and PGC‐1α mRNA after blood flow‐restricted running is related to fibre type‐specific AMPK signalling and oxidative stress in human muscle

  Author(s)

  D. Christiansen R. M. Murphy J. Bangsbo C. G. Stathis D. J. Bishop

  Date

  2018-02-28

  Source

  Acta Physiologica

  Aim
  This study explored the effects of blood flow restriction (BFR) on mRNA responses of PGC‐1α (total, 1α1, and 1α4) and Na+,K+‐ATPase isoforms (NKA; α1‐3, β1‐3, and FXYD1) to an interval running session and determined whether these effects were related to increased oxidative stress, hypoxia, and fibre type‐specific AMPK and CaMKII signalling, in human skeletal muscle.

  Methods
  In a randomized, crossover fashion, 8 healthy men (26 ± 5 year and 57.4 ± 6.3 mL kg−1 min−1) completed 3 exercise sessions: without (CON) or with blood flow restriction (BFR), or in systemic hypoxia (HYP, ~3250 m). A muscle sample was collected before (Pre) and after exercise (+0 hour, +3 hours) to quantify mRNA, indicators of oxidative stress (HSP27 protein in type I and II fibres, and catalase and HSP70 mRNA), metabolites, and α‐AMPK Thr172/α‐AMPK, ACC Ser221/ACC, CaMKII Thr287/CaMKII, and PLBSer16/PLB ratios in type I and II fibres.

  Results
  Muscle hypoxia (assessed by near‐infrared spectroscopy) was matched between BFR and HYP, which was higher than CON (~90% vs ~70%; P < .05). The mRNA levels of FXYD1 and PGC‐1α isoforms (1α1 and 1α4) increased in BFR only (P < .05) and were associated with increases in indicators of oxidative stress and type I fibre ACC Ser221/ACC ratio, but dissociated from muscle hypoxia, lactate, and CaMKII signalling.

  Conclusion
  Blood flow restriction augmented exercise‐induced increases in muscle FXYD1 and PGC‐1α mRNA in men. This effect was related to increased oxidative stress and fibre type‐dependent AMPK signalling, but unrelated to the severity of muscle hypoxia, lactate accumulation, and modulation of fibre type‐specific CaMKII signalling.

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• The comparison of the field and laboratory walk representative characteristics

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  The comparison of the field and laboratory walk representative characteristics

  Author(s)

  Pavel Korvas, Tomáš Kalina, Radek Musil

  Date

  2013-11-07

  Source

  Sport and Quality of Life 2013. 2013. ISBN 978-80-210-6439-3

  In this pilot study we occupy ourselves with the comparison of the basic kinetic and time variables of walk in thefield and on the treadmill. The walk on the treadmill has its own specifics, because the walker doesn’t move in space, the walking belt is in motion. Therefore we suppose that the vertical plantar forces characteristics of stance could be different in comparison with walk in natural environment. Three persons were investigated, man 56 years old, 173 cm, 72 kg, man 20 years, 180 cm 67 kg, woman 19 years, 171 cm, 67 kg. Vertical plantar forces (VGF) and time characteristics were measured by the Pedar Mobile System (Novel GmbH, Munich, Germany). Probands made natural individual walk on flat and uphill land (9 %) at speed 3, 4 and 5 km/ hour. For the laboratory research the treadmill Lode Katana Sport 30 (Groningen, NED) was used. For the field research was used a pavement in the vicinity of the faculty. The speed during field research was checked with the help of cyclocomputer. Before the research the accuracy of computer measurement was compared repeatedly with Sport Photocell Timing (error till 10 %). Seven representative force and time parameters was selected: F1- maximal vertical plantar force during absorption stage of stance (LR, MSt), F2 –the lowest vertical plantar force between both peaks, F3 – maximal vertical plantar force during propulsive stage of stance (TSt, PSw), Fm – average vertical plantar force for whole stance, t – total time of stance, t1 – time of absorption stage of stance, t2 – time of propulsive stage of stance. The probands walked for 15 sec and the last 10 sec was recorded. We evaluated three successive stances of left and right legs. Basic descriptive statistics was used (Mean, SD, percentage) and Effect of Size (Cohen d coefficient). For kinetic parameters (F1, F3) were found out the tendency of increasing values in concordance of increasing speed of walk in the both tests conditions and for F2 was found the tendency of decreasing VGF for all the probands. For each of these parameters was found nearly all differences among field and laboratory significant. The values of F3 were always bigger in field and also values for F1 of two probands. Fm showed insignificant increase of VGR for all the speeds and terrain. The time of stance was reduced with increasing speed of walk in both environments. The time differences of stance between field and laboratory were mostly significant, which is not very logical for the same speed of walk. The shorter time of stance with increasing velocity of walk was caused in the first place of propulsive stage time reduction. The pilot research showed a kinetic and time differencebetween walk in field and laboratory and it indicates the needs of follow-up survey of this topic.

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• Within-day Energy Deficiency and Metabolic Perturbation in Male Endurance Athletes

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  Within-day Energy Deficiency and Metabolic Perturbation in Male Endurance Athletes

  Author(s)

  Monica K. Torstveit, Ida Fahrenholtz, Thomas B. Stenqvist, Øystein Sylta, Anna Melin

  Date

  2018-03-09

  Source

  Human Kinetics Journals

  Endurance athletes are at increased risk of relative energy deficiency associated with metabolic perturbation and impaired health. We aimed to estimate and compare within-day energy balance (WDEB) in male athletes with suppressed and normal resting metabolic rate (RMR) and explore if within-day energy deficiency (WDED) is associated with endocrine markers of energy deficiency. Thirty-one male cyclists, triathletes, and long-distance runners recruited from regional competitive sports clubs were included. The protocol comprised measurements of RMR by ventilated hood, and energy intake and energy expenditure to predict RMRratio (measured RMR/predicted RMR), energy availability (EA), 24-hour energy balance (EB) and WDEB in 1-hour intervals, assessment of body-composition by dual-energy X-ray absorptiometry, and blood plasma analysis. Subjects were categorized as having suppressed (RMRratio < 0.90, n=20) or normal RMR (RMRratio > 0.90, n=11). Despite no observed differences in 24-hour EB or EA between the groups, subjects with suppressed RMR spent more time in an energy deficit exceeding 400 kcal (20.9 [18.8 – 21.8] hours vs. 10.8 [2.5 – 16.4], P=0.023), and had larger single-hour energy deficits compared to subjects with normal RMR (3265 ± 1963 kcal vs. -1340 ± 2439, P=0.023). Larger single-hour energy deficits were associated with higher cortisol levels (r = -0.499, P=0.004) and a lower testosterone:cortisol ratio (r = 0.431, P=0.015), but no associations with T3 or fasting blood glucose were observed. In conclusion, WDED was associated with suppressed RMR and catabolic markers in male endurance athletes.

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