Biomedical subjects

O Verbitsky

Publications and source records attributed to O Verbitsky.

5 recordsLinked to original sources

PubMed2001

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.

Adult↗

PubMed2000

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.

Acceleration↗

PubMed2000

Fatigue-related loading imbalance on the shank in running: a possible factor in stress fractures.

In 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.

Acceleration↗

PubMed1997

Effect of ingested sodium bicarbonate on muscle force, fatigue, and recovery.

The influence of acute ingestion of NaHCO3 on fatigue and recovery of teh quadriceps femoris muscle after exercise was studied in six healthy male subjects. A bicycle ergometer was used for exercising under three loading conditions: test A, load corresponding to maximal oxygen consumption; test B, load in test A + 17%; test C, load in test B but performed 1 h after acute ingestion of NaHCO3. Functional electrical stimulation (FES) was applied to provoke isometric contraction of the quadriceps femoris. The resulting knee torque was monitored during fatigue (2-min chronic FES) and recovery (10-s FES every 10 min, for 40 min). Quadriceps torques were higher in the presence of NaHCO3 (P < 0.05): with NaHCO3 the peak, residual, and recovery (after 40 min) normalized torques were, respectively, 0.68 +/- 0.05 (SD), 0.58 +/- 0.05, and 0.73 +/- 0.05; without NaHCO3 the values were 0.45 +/- 0.04, 0.30 +/- 0.06, and 0.63 +/- 0.06. The increased torques obtained after acute ingestion of NaHCO3 indicate the possible existence of improved nonoxidative glycolysis in isometric contraction, resulting in reduced fatigue and enhanced recovery.

Administration, Oral↗

PubMedDate not supplied

Dynamic thermography: analysis of hand temperature during exercise.

Exercise 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 max, the temperature decrease rate was - 0.0075+/-0.001 degrees C/s during a time interval of 390+/-47 s and the temperature increase rate was 0.0055+/-0.0031 degrees 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 degrees 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.

Adult↗