Animals ; Calcitonin Gene-Related Peptide ; physiology ; Heart ; physiology ; Male ; Physical Exertion ; physiology ; Rats ; Rats, Sprague-Dawley

OBJECTIVETo assess the effect of oxidative stress in development of acute high altitude response (AHAR) during the process of strong physical work at high altitude and its change after return to lower altitude.

METHODSNinety-six officers and soldiers of rapid entering into high altitude (3 700 m) with strong physical work were analyzed, all subjects were male, aged 18-35 years. According to the symptomatic scores of AHAR were divided into 3 groups: severe AHAR (group A, n = 24), mild AHAR (group B, n = 47) and without AHAR (group C, n = 25). Levels in serum 8-iso prostaglandinF2alpha(8-iso-PGF2alpha), superoxide dismutase (SOD) and malonaldehyde (MDA) were measured at higher altitude stayed 50 d and after return to lower altitude (1 500 m) 12 h and 15 d, and 50 healthy volunteers (group D) at 1 500 m altitude served as controll.

RESULTSLevels of serum 8-iso-PGF2alpha and MDA [(9.53 +/- 0.47) microg/L, (8.91 +/- 0.39) micromol/L] were significantly higher in group A than those in group B [(8.34 +/- 0.42) microg/L, (7.31 +/- 0.32) micromol/L] , group C [(7.02 +/- 0.48) microg/L, (6.41 +/- 0.23) micromol/L] and group D [(5.13 +/- 0.56) microg/L, (5.48 +/- 0.33) micromol/L], (all P < 0.01), and serum SOD [(52.08 +/- 3.44) micro/ml] was significantly lower in group A than that in group B [62.27 +/- 2.54) micro/ml], group C [(71.99 +/- 3.35) micro/ml] and group D [(80.78 +/- 3.44) micro/ ml] (all P < 0.01), there were significant differences between group B and C, C and D (all P < 0.01). At altitude 3 700 m 50 d, AHAR scores was positively correlated with serum 8-iso-PGF2alpha and MDA (all P < 0.01), negatively correlated with SOD (P < 0.01). Serum 8-iso-PGF2alpha and MDA were negatively correlated with SOD (all P < 0.01). Levels of serum 8-iso-PGF2alpha and MDA were significantly higher at altitude of 3 700 m 50 d than those at altitude of 1 500 m 12 h,15 d in group D (all P < 0.01), and serum SOD was significantly lower than that at 1 500 m 12 h,15 d in group D (all P < 0.01), there were significantly difference between at 1 500 m 12 h and 15 d (all P < 0.01), there were no difference between at 15 d in group D (all P > 0.05).

CONCLUSIONThe more serious of oxidative stress and oxidative/antioxidative imbalance, the more serious of AHAR, oxidative stress and oxidative/antioxidative imbalance may be involved in the development of AHAR. The changes were obviously improved after return to lower altitude 12 h, and recovered to normal after 15 d.

Adolescent ; Adult ; Altitude ; Altitude Sickness ; physiopathology ; Humans ; Male ; Oxidative Stress ; physiology ; Physical Exertion ; physiology ; Young Adult

OBJECTIVETo observe the modulatory effect of subthalamic nucleus (STN) on activity of motor cortex during exhausting exercise.

METHODSElectrocorticogram (ECoG) and local field potentials (LFPs) recording techniques were applied simultaneously to observe the dynamic changes of oscillations in sensorimotor area and STN of rat during exhausting exercise.

RESULTSRats ran well initiatively with treadmill at the beginning of the exercise, about 45 min (45 +/- 11.5) later, movement capacity reduced. Corresponding electrical property showed that STN activity increased significantly while activity of cortex decreased significantly. Subsequently rats continued exercise with minor external stimulation utill exhaustion. Activity of ECoG reached the minimum under exhausting stations (P < 0.01), while the activity of LFPs changed insignificantly (P > 0.05).

CONCLUSIONDuring the exhausting exercise, the cortex activity was extensively depressed with the development of fatigue, while the activity of STN increased significantly at the early stage of fatigue, STN took part in the modulation of central fatigue through negative induction. And the increase of STN activity may be one of the key measures accounting for protective inhibition.

Animals ; Cerebral Cortex ; physiology ; Electrophysiological Phenomena ; physiology ; Male ; Neurons ; physiology ; Physical Conditioning, Animal ; physiology ; Physical Exertion ; physiology ; Rats ; Rats, Wistar ; Subthalamic Nucleus ; physiology

Respirator breathing resistance impacts performance of wearers during constant work load. However, it is less clear as to how breathing resistance affects the tolerant capacity of users during graded work load. The present study investigated the tolerant capacity of 8 individuals during incremental work load. The 8 subjects were required to wear two matched respirators (respirators I and II which were designed to have different breathing resistances and the same dead space) respectively on separate days and then work to end points. Minute ventilation (V(E)), breathing frequency (BF), oxygen consumption (VO(2)) and heart rate (HR) were recorded during exercise, while tolerant time, response time and breathing discomfort were measured at the end of each test trial. The test variables were compared between the two respirators by using matched-pairs t-test. The results showed that the tolerant time was significantly reduced for the respirator I with higher level of breathing resistance when compared with its counterpart with lower breathing resistance (respirator II) (P<0.05). The same changes occurred for response time. Results also showed a significant increase in V(E) and BF for respirator I wearers when the work load was above 125 W. The O(2) consumption was similar under the two breathing resistance conditions. These findings suggested that the respiratory resistance caused by self-contained breathing apparatus (SCBA) has an impact on the tolerant capacity of users.
Airway Resistance ; physiology ; Exercise ; physiology ; Exercise Tolerance ; physiology ; Humans ; Male ; Oxygen Consumption ; physiology ; Physical Exertion ; physiology ; Respiration, Artificial ; methods ; Respiratory Mechanics ; physiology ; Young Adult

OBJECTIVETo investigate the metabolic changes of mice serum after loaded swimming and to provide a basis for the study of anti-fatigue functional food.

METHODSThe male Kunming mice were randomly divided into four group, fed an AIN-93 diet for 14 days, and forced to swim for 30, 60 or 120 min, respectively, with a load on their tails. The mice were executed after swimming immediately and the changes of serum metabolic profiles were analyzed using metabolomic approach. The spectrum was acquired by using Carr Purcell Meiboom Gill (CPMG) or Longitudinal Eddy Current Delay (LED) sequence, and transformed into 1H NMR spectrogram via Fourier transformation. All the data were analyzed by principal component analysis by using the SIMCA-P+ software.

RESULTSThe serum metabolic profiles changed significantly after loaded swimming. Serum beta-hydroxybutyric acid, acetate, lactate, lipid were increased and glucose, choline, phosphorylcholine, alanine and phosphatidylcholine decreased. These changes were time dependent.

CONCLUSIONThe changes of serum metabolic profiles after loaded swimming were time dependent, especially for lipid metabolite.Further study based on the interaction of choline and lipid metabolism may contribute to understand the mechanism of fatigue.

Animals ; Choline ; metabolism ; Fatigue ; blood ; metabolism ; physiopathology ; Lipid Metabolism ; Male ; Metabolome ; Mice ; Physical Exertion ; physiology ; Swimming ; physiology

OBJECTIVETo evaluate the work load and related factors for asymmetric lifting tasks using surface electromyography (EMG).

METHODSThirteen male volunteers lifted loads of 6 and 13 kg at two speeds, in varying angles of trunk rotation, from floor to knuckle height, performing 16 lifting tasks. During lifting, surface electromyography signals from the erector spinae, bilaterally at level of T10 and L3, was continually recorded. The work load and related factors for asymmetric lifting tasks were evaluated by comparing the average amplitude of EMG signals.

RESULTSThe EMG average amplitude when lifting the load of 13 kg (43.30% MVE) was significantly greater than that when lifting the load of 6 kg (37.70% MVE) (P < 0.01). The EMG average amplitude when lifting at the higher speed (41.80% MVE) was significantly greater than that at the lower speed (39.19% MVE) (P < 0.05). The EMG average amplitude was increased with the increase of the trunk rotation angle without significant difference (P > 0.05). At T10, the EMG average amplitude was greater on the right side than that on the left side (50.31% MVE and 25.88% MVE respectively) while at L3, it was on the contrary (45.60% MVE on the left and 40.22% MVE on the right respectively) (P < 0.01). Multiple stepwise regression analysis showed that the load of lifting was the factor contributing most to the EMG average amplitude followed by the lifting speed.

CONCLUSIONThe risk factors related to work load for asymmetric lifting tasks are mainly the load and the speed of lifting. The EMG activity between the right and left side of erector spinae is different during such lifting.

Adult ; Electromyography ; Humans ; Lifting ; Male ; Multivariate Analysis ; Muscle, Skeletal ; physiology ; Occupational Health ; Physical Exertion ; physiology ; Regression Analysis ; Risk Factors ; Workload

OBJECTIVETo explore the maximum acceptable weight of lift (MAWL) in different lifting conditions and the suitable lifting equation for the stipulation of occupational health standard of manual lifting tasks in China.

METHODSThe MAWL was investigated among the thirteen male and ten female students using psychophysical methodology and the recommended weight of limit (RWL) was compared.

RESULTSThe MAWL of male and female subjects was decreased gradually with the increase of lifting height. Once the height of lifting was over shoulder, the MAWL was decreased dramatically. The RWL was greater than the MAWL at 25 cm horizontal distance in male subjects, but the RWL was smaller than the MAWL at the distance of 45 cm and 63 cm. The average MAWL of male subjects was 30.8% greater than that of female subjects. The MAWL was decreased gradually with increase of the horizontal distance at the same height of lifting. The result of the male subjects was consistent with that of the female subjects. For the asymmetric lifting tasks of the male subjects, the bigger the angle of rotation was, the less the MAWL became. The angle of rotation had negative correlation with the capability of lifting (r = -0.996 6, P < 0.01). When the subjects performed asymmetric lifting tasks, the RWL was smaller than the MAWL and the difference was significant.

CONCLUSIONThe revision is sufficient for the horizontal distance and asymmetric lifting in the NIOSH lifting equation, but it is not suitable for height, especially for the task of lifting over shoulder. The RWL for the task of lifting over shoulder should be lowered. The factor of gender should be taken into account in the lifting equation and the constant of gender S can be added. Then S = 1 for male while S = 0.692 for female.

Adult ; China ; Ergonomics ; standards ; Female ; Humans ; Lifting ; Male ; Occupational Health ; Physical Exertion ; physiology ; Threshold Limit Values ; Weight-Bearing ; physiology

BACKGROUNDOur previous study has confirmed that one bout of exhaustion (Ex) can cause hippocampus neurocyte damage, excessive apoptosis, and dysfunction. Its initial reason is intracellular calcium overload in hippocampus triggered by N-methyl-D-aspartic acid receptor (NMDAR) over-activation. NMDAR activation can be suppressed by γ-aminobutyric acid (A) receptor (GABAAR). Whether GABAAR can prevent intense exercise-induced hippocampus apoptosis, damage, or dysfunction will be studied in this study.

METHODSAccording to dose test, rats were randomly divided into control (Con), Ex, muscimol (MUS, 0.1 mg/kg) and bicuculline (BIC, 0.5 mg/kg) groups, then all rats underwent once swimming Ex except ones in Con group only underwent training. Intracellular free calcium concentration ([Ca2+]i) was measured by Fura-2-acetoxymethyl ester; glial librillary acidic protein (GFAP) and synaptophysin (SYP) immunofluorescence were also performed; apoptosis were displayed by dUTP nick end labeling (TUNEL) stain; endoplasmic reticulum stress-induced apoptosis pathway was detected by Western blotting analysis; Morris water maze was used to detect learning ability and spatial memory.

RESULTSThe appropriate dose was 0.1 mg/kg for MUS and 0.5 mg/kg for BIC. Ex group showed significantly increased [Ca2+]i and astrogliosis; TUNEL positive cells and levels of GFAP, B cell lymphoma-2 (Bcl-2) associated X protein (Bax), caspase-3, caspase-12 cleavage, CCAAT/enhancer binding protein homologous protein (CHOP), and p-Jun amino-terminal kinase (p-JNK) in Ex group also raised significantly compared to Con group, while SYP, synapse plasticity, and Bcl-2 levels in Ex group were significantly lower than those in Con group. These indexes were back to normal in MUS group. BIC group had the highest levels of [Ca2+]i, astrogliosis, TUNEL positive cell, GFAP, Bax, caspase-3, caspase-12 cleavage, CHOP, and p-JNK, it also gained the lowest SYP, synapse plasticity, and Bcl-2 levels among all groups. Water maze test showed that Ex group had longer escape latency (EL) and less quadrant dwell time than Con group; all indexes between MUS and Con groups had no significant differences; BIC had the longest EL and least quadrant dwell time among all groups.

CONCLUSIONSActivation of GABAA R could prevent intense exercise-induced synapses damage, excessive apoptosis, and dysfunction of hippocampus.

Animals ; Apoptosis ; physiology ; Body Weight ; physiology ; Endoplasmic Reticulum Stress ; physiology ; Hippocampus ; metabolism ; Male ; Physical Exertion ; physiology ; Rats ; Rats, Sprague-Dawley ; Receptors, GABA ; genetics ; metabolism ; Synapses ; pathology

A hybrid method based on optimization and force-EMG relationships for predicting muscle force was presented and applied to the flexion movement of upper limb. The results were compared with those from classical optimization and from the method based on force-EMG relationships. The classical optimization can not predict the force of antagonistic muscles. The method based on force-EMG relationships can not satisfy the mechanical equilibrium. The hybrid method overcomes the two disadvantages, but the forces predicted by it fluctuate excessively. Now the hybrid method is just appropriate for use in predicting isometric and isokinetic movements.
Algorithms ; Electromyography ; methods ; Forecasting ; Humans ; Isometric Contraction ; physiology ; Models, Biological ; Muscle Contraction ; physiology ; Muscle, Skeletal ; physiology ; Physical Exertion ; physiology ; Stress, Mechanical

Pushing and pulling (P&P) is a common operating mode of operator's physical works, and plays an important role in evaluation of human behavior health and operation performance. At present, there are many research methods of P&P, and this article is a state-of-art review of the classification of P&P research methods, the various impact factors in P&P program, technical details of internal/external P&P force measurement and evaluation, the limitation of current research methods and the future developments in the ergonomics field.
Biomechanical Phenomena ; Ergonomics ; methods ; Hand Strength ; physiology ; Humans ; Low Back Pain ; prevention & control ; Physical Exertion ; Posture ; physiology ; Task Performance and Analysis ; Weight-Bearing ; physiology