Oleg Verbitsky

Effect of fatigue on leg kinematics and impact acceleration in long distance running

The eAect of fatigue on impact acceleration on the shank, stride rate, knee angle and hip vertical excursion was studied in 14 subjects in 30 minutes treadmill running above their anaerobic threshold (AT) speeds. Respiratory data were collected to determine the AT speed and to indicate the progressively developing fatigue. The following changesOP < 0:05U were obtained from the 1st to the 30th minute of running: average stride rate decreased from 1:46 0:05 to 1:39 0:03 seconds ˇ1 ; average angle at maximal knee extension position increased from 13:8 3:1∞ to 17:2 4:2∞; average knee flexion resulting from foot strike decreased from 13:6 6:3∞ to 8:1 3:0∞; average hip vertical excursion between highest position to peak acceleration position increased from 5:1 1: 5t o 6:2 1:2 cm. The average impact acceleration on the shank, measured by means of an accelerometer attached to the tibial tuberosity, increased from 6:9 2: 9t o 11:1 4:2 g. It was concluded that the obtained kinematic changes due to fatigue were consistent with the substantially higher impact accelerations, increasing the risk of overload injuries in the shank. ” 2000 Elsevier Science B.V. All rights reserved. PsycINFO classification: 2330; 2540; 4010

Fatigue-Related Loading Imbalance on the Shank in Running: A Possible Factor in Stress Fractures

AbstractIn previous reports we have shown that in long distance running the impact acceleration on the shank increases with progressing fatigue. The aim of the present study was to test whether, in parallel to this increase, an imbalance in the activities between the ankle plantar and dorsi flexor muscles develops. The tests were made on fourteen subjects during 30 min treadmill running above their anaerobic thresholds. Respiratory data were collected to determine the anaerobic threshold speed and to indicate the progressively developing metabolic fatigue. Surface electromyogram (EMG) was monitored to indicate the changing activity of the shank muscles. In the tibialis anterior the average integrated EMG (iEMG) and the mean power frequency (MPF) significantly decreased from the beginning to the end of running. In the gastrocnemius iEMG did not change, while MPF increased during the course of running. The impact acceleration, measured by means of an accelerometer attached to the tibial tuberosity, significantly increased during the course of running. It was concluded that, with developing fatigue, an imbalance in the contraction of the shank muscles develops in parallel to an increase in shank shock acceleration. The combination of these two changes may hamper the loading balance on the tibia since the bone becomes exposed to excessive bending stresses and to higher risk of stress injury.

Dynamic loading on the human musculoskeletal system —effect of fatigue

OBJECTIVE: A study was conducted to investigate the effects of fatigue on the ability of human musculoskeletal system to deal with the onslaught of the heel strike initiated shock waves. DESIGN: Running on a treadmill at the anaerobic threshold level for 30 min was used to acquire the experimental data on the foot strike initiated shock waves. BACKGROUND: Muscles act to lower the bending stress on bone and to attenuate the dynamic load on human musculoskeletal system. Fatigue may diminish their ability to dissipate and attenuate loading on the system. Knowledge of the effects of fatigue on the ability of the human musculoskeletal system to attenuate the shock waves may help in design of the training procedures and exercises. METHODS: Twenty-two young healthy males participated in this study. Each one was running on the treadmill at the speed corresponding to his anaerobic threshold for 30 min. The heel strike induced shock waves were recorded every 5 min on the tibial tuberosity and sacrum. The data obtained were analyzed in both temporal and frequency domains. RESULTS: The results reveal significant increase in the dynamic loading experienced by the human musculoskeletal system with fatigue. This may be attributed to the inability of the fatigued system to provide an efficient way to attenuate shock waves. CONCLUSIONS: The analysis of the recorded signals suggests that fatigue contributes to the reduction of the human musculoskeletal systems capacity to attenuate and dissipate those shock waves. This capacity appears to be a function not only of the fatigue level, but also of the vertical location along the skeleton. RELEVANCE: Fatigue during running may affect the ability of the human musculoskeletal system to attenuate and dissipate the heel strike induced shock waves. The study of the fatigue effect on shock wave attenuation provides information that may benefit the runner.

Dynamic Thermography: Analysis of Hand Temperature During Exercise

AbstractExercise has a noted effect on skin blood flow and temperature. We aimed to characterize the normal skin temperature response to exercise by thermographic imaging. A study was conducted on ten healthy and active subjects (age=25.8 ± 0.7 years) who were exposed to graded exercise for determination of maximal oxygen consumption (VO2 max), and subsequently to constant loads corresponding to 50%, 70%, and 90% of VO2 max. The skin temperature response during 20 min of constant load exercise is characterized by an initial descending limb, an ascending limb and a quasi-steady-state period. For 50% VO2 the temperature decrease rate was --0.0075±0.001°C/s during a time interval of 390 ±47 s and the temperature increase rate was 0.0055 ± 0.0031 °C/s during a time interval of 484 ±99 s. The level of load did not influence the temperature decrease and increase rates. In contrast, during graded load exercise, a continuous temperature decrease of --0.0049 ± 0.0032 °C/s was observed throughout the test. In summary, the thermographic skin response to exercise is characterized by a specific pattern which reflects the dynamic balance between hemodynamic and thermoregulatory processes.

Shock Transmission and Fatigue in Human Running

The goal of this research was to analyze the effects of fatigue on the shock waves generated by foot strike. Twenty-two subjects were instrumented with an externally attached, lightweight accelerometer placed over the tibial tuberosity. The subjects ran on a treadmill for 30 min at a speed near their anaerobic threshold. Fatigue was established when the end-tidal CO2 pressure decreased. The results indicated that approximately half of the subjects reached the fatigue state toward the end of the test. Whenever fatigue occurred, the peak acceleration was found to increase. It was thus concluded that there is a clear association between fatigue and increased heel strike-induced shock waves. These results have a significant implication for the etiology of running injuries, since shock wave attenuation has been previously reported to play an important role in preventing such injuries.

Shock accelerations and attenuation in downhill and level running

OBJECTIVE A study was conducted to investigate the possible effects of fatigue on the heel strike-initiated shock accelerations and on attenuation of these shocks along the body during eccentric muscle contractions. DESIGN Level and decline running on a treadmill were used to acquire the experimental data on the foot strike-initiated shock accelerations. BACKGROUND Eccentric contractions of the lower limb muscles in combination with shock generation and propagation during downhill running and muscle fatigue may diminish their ability to dissipate and attenuate loading on the system. METHODS Fourteen young healthy males ran on a treadmill at a speed exceeding their anaerobic threshold by 5% for 30 min, as follows: (a) level running and (b) downhill running with a decline angle of -4 degrees. The foot strike-induced shock accelerations were recorded every five minutes on the tibial tuberosity and sacrum. Fatigue was monitored by means of the respiratory parameters. RESULTS The downhill running related with eccentric muscle contractions was associated with increased shock propagation from the tibial tuberosity to the sacrum levels, even though fatigue did not develop. CONCLUSIONS Shock propagation from the tibial tuberosity to the sacrum is augmented due to the eccentric action of the muscles, without metabolic fatigue development. RELEVANCE Eccentric muscle contraction in downhill running reduces the musculoskeletal ability to attenuate the heel strike-induced shock waves. Knowledge about the effect of fatigue on the shock propagation between the shank and the sacrum levels may help in understanding the mechanism of stress fractures and joint damage.

Fatigue-induced changes in decline running.

OBJECTIVE Study the relation between muscle fatigue during eccentric muscle contractions and kinematics of the legs in downhill running. DESIGN Decline running on a treadmill was used to acquire data on shock accelerations, muscle activity and kinematics, for comparison with level running. BACKGROUND In downhill running, local muscle fatigue is the cause of morphological muscle damage which leads to reduced attenuation of shock accelerations. METHODS Fourteen subjects ran on a treadmill above level-running anaerobic threshold speed for 30 min, in level and -4 degrees decline running. The following were monitored: metabolic fatigue by means of respiratory parameters; muscle fatigue of the quadriceps by means of elevation in myoelectric activity; and kinematic parameters including knee and ankle angles and hip vertical excursion by means of computerized videography. Data on shock transmission reported in previous studies were also used. RESULTS Quadriceps fatigue develops in parallel to an increasing vertical excursion of the hip in the stance phase of running, enabled by larger dorsi flexion of the ankle rather than by increased flexion of the knee. CONCLUSIONS The decrease in shock attenuation can be attributed to quadriceps muscle fatigue in parallel to increased vertical excursion of the hips.

LEED-NCV3 SILVER AND GOLD CERTIFIED PROJECTS IN THE US: AN OBSERVATIONAL STUDY

Abstract The Leadership in Energy and Environmental Design (LEED) rating system has been widely used in the US. However, until now, there has been no clear understanding of the strategies that should be used to make the transition from Silver to Gold certified projects. The aim of this study was to determine the trends in certified projects for both Silver and Gold LEED for New Construction and Major Renovations (LEED-NCv3) in 2016. Three performances, including (i) certification, (ii) category/subcategory/sub-subcategory certification, and (iii) cross-certification, were evaluated for both Silver and Gold LEED-NCv3 certified projects. For an ordinal measurement scale, a two-tailed Mann-Whitney U test was used. For a ratio measurement scale, an unpaired two-tailed t-test was used. If eight or more Silver and Gold certified projects occurred in the same state, then the state was selected for statistical analysis. As a result, ten states were selected. The following was revealed: (i) low certification perfo...

A Single-Unit Design Structure and Gender Differences in the Swimming World Championships

Abstract Four 50 meter male/female finals - the freestyle, butterfly, breaststroke, and backstroke - swum during individual events at the Swimming World Championships (SWCs) can be defined in four clusters. The aim of the present study was to use a single-unit design structure, in which the swimmer was defined at only one scale, to evaluate gender differences in start reaction times among elite swimmers in 50 m events. The top six male and female swimmers in the finals of four swimming stroke final events in six SWCs were analyzed. An unpaired t-test was used. The p-values were evaluated using Neo-Fisherian significance assessments (Hurlbert and Lombardi, 2012). For the freestyle, gender differences in the start reaction times were positively identified for five of the six SWCs. For the backstroke, gender differences in the start reaction times could be dismissed for five of the six SWCs. For both the butterfly and breaststroke, gender differences in the start reaction times yielded inconsistent statistical differences. Pooling all swimmers together (df = 286) showed that an overall gender difference in the start reaction times could be positively identified: p = 0.00004. The contrast between the gender differences in start reaction times between the freestyle and backstroke may be associated with different types of gender adaptations to swimming performances. When the natural groupings of swimming stroke final events were ignored, sacrificial pseudoreplication occurred, which may lead to erroneous statistical differences

LIFE CYCLE ASSESSMENTS OF WHITE FLAT AND RED OR WHITE PITCHED ROOFS FOR RESIDENTIAL BUILDINGS IN ISRAEL

ABSTRACT Historically, white flat roofs have been used in Israel due to the intense solar radiation and long, hot, rainless summers. However, red pitched roofs have also been frequently used for aesthetic reasons. It has been recently observed that red pitched roofs have been recolored white by homeowners. The goal of this study was to compare the life cycle assessments (LCAs) of white flat roofs versus red or white pitched roofs through their production (P), operational energy (OE), and maintenance to disposal (MtoD) stages. EnergyPlus software was used to evaluate the OE stage. The ReCiPe method was used to evaluate the environmental damages in all the stages. A two-stage nested ANOVA was used to determine the significant differences between the ReCiPe result of a white flat roof and the ReCiPe result of a red/white pitched roof. It was found that (i) selection of the best roof technology (flat or pitched) requires consideration of the LCA, including the P, OE, and MtoD stages; (ii) the white (flat and ...