Effects of Panax notoginseng (Chinese ginseng) and acute exercise on postprandial glycemia in non-diabetic adults.

The purpose of this study is to determine whether Panax Notoginseng (PNG) taken for 3 days and one 30-min cycling exercise can reduce postprandial hyperglycemia after ingesting a 75-mg oral glucose solution (OGTT) in untrained non-diabetic men, age 20-45 years. We randomly assigned 52 men to: 1) ginseng (G) + exercise (G+Ex, n=14), 2) ginseng (G, n=13), 3) placebo (C) + exercise (C+Ex, n=12), and 4) placebo control groups (C, n=13). The G and C groups took a daily 3g dose of PNG and cornstarch-placebo supplement for 3 days, respectively. The exercise groups also performed a 30-min cycling exercise on day 3 prior to OGTT. The daily 3g-dose of PNG supplementation significantly lowered postprandial plasma glucose (PG) concentration at 30 min post-OGTT in the G group, compared with C (mean Δ±SE: G vs. C = 26.3±11 mg/dl, p<0.05) and PG area under the curve (PG-AUC0-90) in the G and G+Ex groups, relative to the C (G vs. C = 96.5±42 and G+Ex vs. C = 85.2±41 mg/dl, both p<0.05). We conclude that a daily 3g-dose of PNG taken for 3 days, not one acute bout of 30-min cycling exercise at 60% VO2max, lowered postprandial glycemia at 30-min post-OGTT and PG-AUC 0-90 min in non-diabetic men, age 20-45 years.

Effect of short-term upper-body resistance training on muscular strength, bone metabolic markers, and BMD in premenopausal women.

UNLABELLED: To examine the effect of a 10-week upper-body resistance training program on bone turnover markers and site-specific bone mineral density (BMD) in the wrist and distal half of the ulna and radius in untrained and healthy young premenopausal women. METHODS: Twenty-two subjects (aged 22.1 ± 1.8 years) were randomly assigned to a resistance training (n = 12) or no training control (n = 10) group. The following outcome variables were measured before and after 10 weeks of resistance training: (1) bone formation biomarker osteocalcin, and bone resorption biomarker tartrate-resistant acid phosphatase isoform 5b; (2) BMD in the wrist and distal half of the ulna and radius; (3) isokinetic strength of the elbow and knee extensors and flexors; (4) dynamic strength of the arm extensors and flexors; and (5) maximum number of push-ups. RESULTS: The 10-week upper body resistance training intervention resulted in improved strength performance in push-ups (resistance training versus control: P < 0.05), chest presses (P < 0.05), and pulldowns (P < 0.05). However, there was no improvement in the BMD of the wrist (P > 0.05), BMD of the distal half of the ulna and radius (P > 0.05), and metabolic biomarkers osteocalcin (P > 0.05) and tartrate-resistant acid phosphatase isoform 5b (P > 0.05), except for the osteocalcin/tartrate-resistant acid phosphatase isoform 5b ratio. Also, no improvement in the resistance training group was observed for isokinetic strength of the knee and elbow flexion/extension. CONCLUSION: Upper-body muscular strength performance, but not bone metabolic markers and BMD of the wrist, can be improved with a 10-week upper body resistance training program of the nonweight-bearing limbs in untrained young premenopausal women.

Mental stress and trapezius muscle activation under psychomotor challenge: a focus on EMG gaps during computer work.

Momentary reductions in the electrical activity of working muscles (EMG gaps) contribute to the explanation for the relationship between psychosocial stress and musculoskeletal problems in computer work. EMG activity and gaps in the left and right trapezii were monitored in 23 participants under low and high mental workload (LMW and HMW) demands during computer data entry. Increases in EMG activity and decreases in EMG-gap frequencies in both left and right trapezius muscles were greater during HMW than LMW. In addition, heart period and end-tidal CO2 were lower during HMW, whereas self-reported mood states were higher during HMW. The correspondence between lower end-tidal CO2 and lower EMG-gap frequencies suggests that hyperventilation (overbreathing) may mediate trapezius muscle activation. The reduction of EMG gaps suggests that the salutary benefits of momentary rest from musculoskeletal work are diminished during mental stress.

The unique relation of physical activity to executive function in older men and women.

PURPOSE: To determine whether physical activity participation was specifically and positively associated with executive function in older individuals after accounting for age, education, and IQ. METHODS: Participants were 120 healthy men (N = 38) and women (N = 82) aged 65-92 yr (mean = 78.9, SD = 5.8), who were free of depression and dementia (Beck Depression Inventory and Mini-Mental Status Exam, respectively), had above-average intelligence (mean = 118.1, SD = 9.4) as indexed by the Kaufman Brief Intelligence Test (K-BIT), and stable patterns of physical activity during a 3- to 5-yr period before the study. Participants completed the Yale Physical Activity Survey (YPAS) for older adults and the Stroop Color and Word Test to assess inhibitory executive function. RESULTS: Hierarchical regression analyses revealed that YPAS summary index scores explained a small, but significant amount of variance in Stroop color-word and interference scores (DeltaR2 = 2 and 4%, respectively) after accounting for intelligence and age. The YPAS index was unrelated to nonexecutive performance. CONCLUSIONS: The results support specificity of the physical activity/cognition relationship in older individuals. The results may be explained by additive benefit from participation in physical activity to the frontal lobe (i.e., beyond any benefits from cognitive stimulation), a region that mediates executive function and experiences accelerated age-related decline. In summary, habitual physical activity is positively related to executive performance in older men and women into the 10th decade.

Electroencephalographic studies of skilled psychomotor performance.

Measurements based on the EEG have featured prominently in shaping present-day concepts of the neurocognitive aspects of skilled performance. The techniques include measurements of spectral power, interelectrode coherence, event-related potential components such as the P300, slow potentials, and the method of cognitive inference. The advantages offered by EEG-based approaches lies in their spatiotemporal resolution (potentially 1 mm and less than 1 millisecond, respectively) and the potential to preserve ecological validity, i.e., to obtain measurements of cortical function under the same conditions that the task is normally performed. These studies indicate that activity is reduced in specific regions of the cerebral cortex of experts relative to that observed in novices. These changes occur over time as a result of practice. The authors argue that such cortical change results in less attentional demand and less cognitive interference with motor planning and execution. The findings attest to the plasticity of the central nervous system when one is engaged in goal-directed learning, and hold implications for understanding how the nervous system acquires voluntary skills, whether in the context of the training of an athlete or the rehabilitation of a patient who has lost motor skills due to a disease of the nervous system.

Aerobic exercise training and cardiovascular reactivity to psychological stress in sedentary young normotensive men and women.

Forty-five (22 women) sedentary young (18-30 years old) nonsmoking normotensive volunteers engaged in either 6 weeks of aerobic training (AT), weight training (WT), or a no-treatment (NT) condition to determine whether AT lowers systolic (SBP) and diastolic (DBP) blood pressure, heart rate (HR), and rate-pressure product (RPP) during rest, psychological stress, and recovery periods. Estimated VO(2)max increased for the AT (32.1+/-1.1 to 38.4+/-1.0 ml.kg(-1).min(-1)). A smaller increase for the WT (30.5+/-1.1 to 33.8+/-1.0) was likely due to increased leg strength, and VO(2)max did not change for the NT (32.5+/-1.1 to 32.9+/-1.0). Heart rate and RPP levels were lower during psychological stress and recovery after training for AT relative to the WT and NT. Overall SBP was also lower in the AT relative to the NT but not the WT. In conclusion, aerobic training lowered cardiovascular activity levels during psychological stress and recovery in healthy young adults, implying a protective role against age-related increases in coronary heart disease for individuals who adopt aerobic exercise early in life and maintain the behavior across the life span.

A hyperventilation theory of job stress and musculoskeletal disorders.

BACKGROUND: There is evidence of a link between job stress and upper extremity work-related musculoskeletal disorders. However, the biobehavioral mechanisms by which psychosocial stress factors contribute to the development of musculoskeletal disorders are uncertain. METHODS: Based on established principles of breathing and job stress and the relevant empirical literatures, a hyperventilation theory of job stress and work-related musculoskeletal disorders was developed. RESULTS: Hyperventilation (overbreathing) refers to a drop in arterial CO2 caused by ventilation that exceeds metabolic demands for O2. Excessive loss of CO2 (increase in rate of flow of CO2 from cells to longs) that results from hyperventilation produces a rise in blood pH (i.e., respiratory alkalosis). This disruption in the acid-base equilibrium triggers a chain of systemic physiological reactions that have adverse implications for musculoskeletal health, including increased muscle tension, muscle spasm, amplified response to catecholamines, and muscle ischemia and hypoxia. Hyperventilation is often characterized by a shift from a diaphragmatic to a thoracic breathing pattern, which imposes biomechanical stress on the neck/shoulder region due to the ancillary recruitment of sternocelidomastoid, scalene, and trapezius muscles in support of thoraci breathing. CONCLUSIONS: A hyperventilation theory provides an innovative framework for understanding how job stress contributes to pathophysiological processes that increase the risk of work-related musculoskeletal disorders. With respect to the control of these disorders, a hyperventilation theory has important implications for establishing effective work organization interventions and individual stress-management methods. In this regard, breathing is a biobehavioral metric for assessing whether psychosocial aspects of work organization are in balance with a worker's needs and resources. A hyperventilation theory also provides a unique rationale for coping with job stress and musculoskeletal discomfort through breathing training, light physical exercise, and rest breaks.