European journal of applied physiology
-
Eur. J. Appl. Physiol. · Nov 2007
The influence of body posture, arm movement, and work stress on trapezius activity during computer work.
The study aimed to determine the influence of arm posture and movement on trapezius activity of computer workers, considering the full workday. A second aim was to investigate if work periods perceived as stressful were associated with elevated or more sustained muscle activity pattern. Twenty-six computer workers performing call-center (n=11), help desk (n=7), or secretarial (n=8) work tasks participated. ⋯ In seated posture (mean duration 79% of workday) arm movement consistently influenced trapezius activity, accounting for approximately 20% of intra-individual variation in trapezius activity. Arm elevation was on average not associated with trapezius activity when seated; however, considerable individual variation was observed. There was no indication of increase in trapezius activity or more sustained activity pattern, nor in heart rate, in high-stress versus low-stress periods, comparing periods with seated posture for the subjects reporting contrasts of at least two VAS units in stress (n=16) or tension (n=14) score.
-
Eur. J. Appl. Physiol. · Sep 2007
Differences in quadriceps muscle strength and fatigue between lean and obese subjects.
The present study aimed to compare quadriceps femoris muscle strength and fatigue between obese (grade II and III) and nonobese adults. Ten obese (mean age: 25 years; mean BMI: 41 kg/m(2)) and ten lean (mean age: 27 years; mean BMI: 23 kg/m(2)) men were tested. Quadriceps muscle fatigue was quantified as the (percent) torque loss during a voluntary isokinetic (50 maximal contractions at 180 degrees /s) and an electrostimulated (40 Hz) isometric protocol (5 min, 10% of the maximal torque). ⋯ Obese individuals demonstrated lower fatigue resistance during voluntary but not during stimulated knee extensions compared to their nonobese counterparts. Peripheral mechanisms of muscle fatigue -- at least those associated to the present stimulated test -- were not influenced by obesity. The observed quadriceps muscle function impairments (voluntary fatigue and relative strength) probably contribute to the reduced functional capacity of obese subjects during daily living activities.
-
Eur. J. Appl. Physiol. · Sep 2007
Targeted brain hypothermia induced by an interstitial cooling device in human neck: theoretical analyses.
In this study, the feasibility of a newly developed interstitial cooling device inserted into the neck muscle and placed on the surface of the common carotid artery is evaluated. A combination of vascular model and continuum model is developed to simulate the temperature fields in both the neck and brain regions. Parametric studies are conducted to test the sensitivity of various factors on the temperature distribution. ⋯ Although the degree of the cooling in the arterial blood is inversely proportional to the blood flow rate of the arteries, the total heat loss from the arterial blood does not vary significantly if the blood flow rate changes during the cooling. After the cold arterial blood is supplied to the brain hemisphere, temperature reduction in the brain tissue is almost uniform and up to 3.1 degrees C temperature drop is achieved within 1 hour. In addition to the possible benefits of brain hypothermia for stroke or head injury patients, the device has the potential to control fever as well as to improve patients' outcome during open neck and head surgery.
-
Eur. J. Appl. Physiol. · Aug 2007
Randomized Controlled TrialThe influence of strength-endurance training on the oxygenation of isometrically contracted forearm muscles.
Ice-climbers frequently use the squeezing of rubber rings for increasing their isometric strength-endurance in the forearm muscles. The aim of this study was to ascertain whether such training influences oxygenation and endurance of forearm muscles at higher as well as lower testing intensities. Fourteen healthy young ice-climbers were divided and randomized into two groups. ⋯ Muscle oxygenation during intense isometric contraction is low in spite of an increase observed in training. This may be due to oxygenation levels that were below the limit where oxygenation may influence the duration of the contraction. Increased oxygenation may have occurred due to an increased blood flow and perfusion through superficial muscles or layers may not have contributed to the generation of the force of the contraction, as would be the case in deeper muscle layers.
-
Eur. J. Appl. Physiol. · Jul 2007
Controlled Clinical TrialAdaptations to long-term strength training of ankle joint muscles in old age.
The aim of this study was to enquire whether older adults, who continue plantar-flexion (PF) strength training for an additional 6-month period, would achieve further improvements in neuromuscular performance, in the ankle PFs, and in the antagonist dorsi-flexors (DFs). Twenty-three healthy older volunteers (mean age 77.4 +/- 3.7 years) took part in this investigation and 12 of them followed a 1-year strength-training program. Both neural and muscular factors were examined during isometric maximal voluntary contraction (MVC) torques in ankle PF and DF pre-training, post 6 and post 12 months. ⋯ The strength training of the agonist PF muscles appeared to have an impact on the maximal resultant torque in DF. However, it appeared that this gain was first due to modifications occurring in the trained PFs muscles, then, it seemed that the motor drive of the DFs per se was altered. In conclusion, long-term strength training of the PFs resulted in continued improvements in neuromuscular performance at the ankle joint in older adults, beyond the initial 6 months.