Reliability of a new measure of motoneuron excitability

Objectlve:--This study examined the intraclass reliability· of different measures of the excitability of the Hoffmann reflex, derived from stimulus-response curves. The slope of the regression line of the H-reflex stimulus-response curve advocated by Funase et al. (1994) was also compared to the peak of the first derivative of the H-reflex stimulus-response curve (dHIdVmax), a new measure introduced in this investigation. A secondary purpose was to explore the possibility of mood as a covariate when measuring excitability of the H-reflex arc. Methods: The H-reflex amplitude at a stimulus intensity corresponding to 5% of the maximum M-wave (Mmax) is an established measure that was used as an additional basis of comparison. The H-reflex was elicited in the soleus for 24 subjects (12 males and 12 females) on five separate days. Vibration was applied to the Achilles tendon prior to stimulation to test the sensitivity of the measures on test day four. The means of five evoked potentials at each gradually increasing intensity, from below H-reflex threshold to above Mmax, were used to create both the H-reflex and M-wave stimulus response curves for each subject across test days. The mood of the subjects was assessed using the Subjective Exercise Experience Scale (SEES) prior to the stimulation protocol each day. Results: There was a modest decrease in all H-reflex measures from the first to third test day, but it was non-significant (P's>0.05). All measures of the H-reflex exhibited a profound reduction following vibration on test day four, and then returned to baseline levels on test day five (P's<0.05). The intraclass correlation coefficient (ICC) for H-reflex amplitude at 5% of Mmax was 0.85. The ICC for the slope of the regression line was 0.79 while it was 0.89 for dH/dVmax. Maximum M-wave amplitude had an ICC of 0.96 attesting to careful methodological controls. The SEES subscales of fatigue and psychological well-being remained unchanged IV across the five days. The psychological distress subscale (PO.05). Conclusions: The peak of the first derivative of the H-reflex stimulus-response curve (dH/dVmax) was shown to have comparable reliability and sensitivity to other more established measures of excitability. Psychological distress and the amplitude of the H-reflex at 5% Mmax follow similar trends across days, however there was no significant correlation between the two measures. Significance: The proposed method appears to be a more robust measure ofH-reflex excitability than the other methods tested. As such it would be an advantageous method to apply in clinical and investigative settings. Additionally, the results suggest that the relationship between psychological distress and H-reflex amplitude should be investigated further.

The impact of the Canadian Standardized Test of Fitness and of health counselling on health attitudes and behaviour

The purpose of this research study was to determine whether or not the use of a single day of Personal Wellness Evaluations would be meaningful enough to change the attitudes of participants toward adopting a healthier lifestyle, or if it was necessary to include regular planned health counselling alon-g with the Personal Wellness Evaluations in order to'observe changes in beliefs, attitudes and behaviours toward active living and the adoption of a healthier lifestyle. Attitudes and behaviours toward physical fitness and healthy lifestyle choices were assessed through a questionnaire composed of the following instruments: Fishbein and Ajzen Attitude and Behaviour Questionnaire, Leisure Behaviour Questionnaire, Ten Centimeter Bipolar Health Continuum, Neugarten Life Satisfaction Assessment, Job Description Index, Selected questions from the Ontario Health Survey, and the Symptom Reporting Questionnaire. Physical fitness evaluation consisted of the Canadian Standardized Test of Fitness, measures of blood pressure, and total cholesterol. The participants were divided into three groups: Group 1- CSTF & health counselling, Group 2- CSTF only, and Group 3- a control group. All three groups received the questionnaire both at the beginning and at the end of the study. Group 1 and Group 2 also participated in fitness testing at these same times, with a three-month time interval between test times. Group 1 also received weekly one-hour health education sessions during the three months between fitness testing. While there were some differences found between the three groups in this study, the results of this study suggested that this three-month workplace wellness program had no impact on the participants' attitudes and behaviours toward health and physical activity. There were no significant differences in the physical fitness measures between Group 1 and Group 2 , nor in the participants' questionnaire responses. These results may be due to the participants' lack of compliance to this wellness program. Employees who 11 participate in a workplace weIlness program must be self-motivated to comply with the program in order to receive the full benefits the program has to offer. Some participants in this study did not have the internal motivation necessary to remain in the study for the three-month period. Future research may consider implementing a workplace wellness program for a longer duration as well as incorporating a specific physical fitness program for the participants to follow. An exercise program could improve the participants' physical fitness, while the health counselling would give the individuals the health education necessary to lead a healthy lifestyle.

The reliability of an isometric test based on constant perception of effort

To date there is no documented procedure to extrapolate findings of an isometric nature to a whole body performance setting. The purpose of this study was to quantify the reliability of perceived exertion to control neuromuscular output during an isometric contraction. 21 varsity athletes completed a maximal voluntary contraction and a 2 min constant force contraction at both the start and end of the study. Between pre and post testing all participants completed a 2 min constant perceived exertion contraction once a day for 4 days. Intra-class correlation coefficient (R=O.949) and standard error of measurement (SEM=5.12 Nm) concluded that the isometric contraction was reliable. Limits of agreement demonstrated only moderate initial reliability, yet with smaller limits towards the end of 4 training sessions. In conclusion, athlete's na"ive to a constant effort isometric contraction will produce reliable and acceptably stable results after 1 familiarization sessions has been completed.

Health-Enhancing Physical Activity and Well-Being: Is it How Often, How Long, or How Much Effort that Matters? A Test of Basic Psychological Needs Theory

The primary objectives of the present study were 1) to examine the relationship between health-enhancing physical activity (HEPA) and well-being across the previous day and 2) to examine the role of basic psychological need satisfaction as a potential mediator of the HEPA – well-being relationship. Participants (N = 203) were a convenience sample of undergraduate students with data collected cross sectionally. HEPA was generally associated with well-being (r‟s ranged from .18 to .62). Multiple mediation analyses supported psychological need satisfaction as mechanisms underpinning the HEPA – well- being relationship. Subsequent analyses demonstrated that effort put forth in HEPA activities, as opposed to frequency or duration, uniquely predicted well-being. The role of effort was further highlighted in the multiple mediation analyses. As such future research may wish to investigate the utility of a HEPA program that facilitates effortful engagement and fulfillment of basic psychological needs.

Effect of increased milk intake combined with endurance exercise training on body composition, blood-lipids and inflammatory markers in overweight young males

Consuming low-fat milk (LFM) after resistance training leads to improvements in body composition. Habitual aerobic exercise and dairy intake are relatively easy lifestyle modifications that could benefit a population at risk for becoming obese. Thus, the purpose of this study was to investigate combining increased LFM intake with endurance exercise on body composition, blood-lipid profile and metabolic markers. 40 young males were randomized into four groups: one ingesting 750mL LFM immediately post-exercise, the other 6hrs post-exercise; and two isocaloric carbohydrate groups ingesting at the two different times. Participants completed a 12 week endurance-training program (cycling 1 hour/day at ~60%VO2peak, 5 days/week). 23 participants completed the study. Increases in lean mass (p < 0.05), and decreases in anti-inflammatory marker adiponectin (p < 0.05) were seen in all groups. No other significant changes were observed. Future analyses should focus on longer duration exercise and include a larger sample.

Influence of timing of milk consumption coupled with endurance training on body composition and endurance training adaptations in humans.

Consumption of low-fat milk (LFM) after resistance training has been shown to have positive influences on body composition and training adaptations; however, little research has examined the effects of LFM consumption following endurance training. The purpose of the study was to look at the effects of combining additional servings of LFM following endurance exercise on body composition, bone health, and training adaptations. 40 healthy males were recruited. Individuals were randomized into 4 groups – DEI (750mL LFM immediately post exercise), DEA (750mL LFM 4 hrs prior to or 6 hrs post exercise), CEI (750mL carbohydrate beverage immediately post-exercise), and CEA (750mL carbohydrate beverage immediately post-exercise). Participants took part in a 12-week endurance training intervention (1 h/day, 3 d/wk, ~60% max HR). 22 participants completed the study. Analysis showed significant increases in lean mass, spinal bone mineral content, relative VO2peak, and a decrease in Trap 5β across all groups (p < 0.05).