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Biomedical subjects

D M Landers

Publications and source records attributed to D M Landers.

At least 19 recordsLinked to original sources
PubMed1998

Motor performance and motor learning as a function of age and fitness.

Past studies have shown that electroencephalographic alpha activity increases as people learn to perform a novel motor task. Additionally, it has been suggested that motor performance and learning decline as people age beyond 60 years, and it has been hypothesized that physical fitness may attenuate this decline through its impact on the cerebral environment. This study was designed to replicate past research by assessing changes in alpha activity as a function of learning and to extend past research by examining differences in motor performance, motor learning, and alpha activity as a function of age and fitness. VO2max was assessed in 41 older (ages 60-80 years) and 42 younger (ages 20-30 years) participants. Participants were randomly assigned to experimental or control conditions, which differed in the amount of practice received. Participants performed trials on the mirror star trace on both an acquisition and a retention day. Results indicated that younger participants performed better and had greater learning than older participants. Fitness was not found to impact either performance or learning. Participants in the experimental group improved more than those in the control group and maintained this difference at retention, which suggests that learning occurred. Associated with these improvements in performance capabilities was an increase in alpha power.

Adult↗
PubMed1997

Planning significant and meaningful research in exercise science: estimating sample size.

Exercise science researchers are familiar with the use of parametric tests to detect significant differences among treatment groups. However, in planning research a question asked with increasing frequency is, "How many participants are needed to detect real and meaningful differences among groups?" In this paper, we provide an overview of the use of alpha, power, and effect size in planning sample sizes that allow tests of real and meaningful differences among groups. Because effect size is the parameter most often missing, we have located meta-analyses in sport and exercise psychology (n = 26), and motor behavior (n = 6). We provide examples and a discussion of how researchers can use these effect sizes along with common estimates of alpha and power to plan for the sample size needed to detect real and meaningful group differences.

Exercise↗
PubMed1996

Changes in electroencephalographic activity associated with learning a novel motor task.

This study was designed to examine changes in EEG activity associated with the learning of a novel task. Right-handed adults (N = 61) were randomly assigned to experimental and control groups. Subjects'EEG was recorded at 10 sites. Subjects' performance was assessed using 8-s trials on a mirror star trace. On the acquisition day, the experimental subjects performed 175 trials while the control subjects performed 10 trials, sat quietly for the amount of time needed to perform 155 trials, and then performed 10 more trials. On the retention day, all subjects performed 20 trials. There was a significant Group x Day x Trial interaction that showed that performance improved across trial blocks and across days; however, after the first 10 acquisition trials, the experimental subjects were always significantly better than the control subjects. Analysis of the EEG data showed a significant four-way interaction that showed that following the the first 10 acquisition trials, the experimental subjects had more alpha activity than the control subjects. It is concluded that there are consistent EEG changes in the alpha band that are associated with learning a motor task.

Adult↗
PubMed1996

The effects of acute and chronic exercise on sleep. A meta-analytic review.

Studies attempting to ascertain the effects of acute and chronic exercise on measures of sleep have yielded conflicting results and interpretations. Methodological differences among studies may explain this lack of consensus; however, small sample sizes and subsequently low statistical power may also have contributed. In an attempt to resolve these issues, this review used meta-analytical techniques to: (a) re-examine the effects of exercise on sleep; and (b) examine possible moderators of these effects. Studies meeting the selection criteria were included in the analysis. Analyses of moderating factors were performed for stage 4 sleep and rapid eye movement (REM) sleep. The results indicated that acute and chronic exercise increased slow wave sleep (SWS) and total sleep time but decreased sleep onset latency and REM sleep. Moderating variables influencing the magnitude and direction of these effects were related to characteristics of the individual (e.g. sex, age, fitness level) and the exercise (e.g. time of day exercise was completed, type of exercise, exercise duration). Mechanisms which have been suggested to explain the relationship between exercise and sleep are discussed and directions for further research are provided.

Exercise↗
PubMed1995

Effect of choline supplementation on fatigue in trained cyclists.

The availability of choline, the precurser of the neurotransmitter, acetylcholine, in the diet is sufficient to provide the body's requirements under normal conditions. However, preliminary evidence indicates that depletion of choline may limit performance, while oral supplementation may delay fatigue during prolonged efforts. A double-blind cross-over design was used to determine the relationship between plasma choline and fatigue during supramaximal brief and submaximal prolonged activities. Twenty male cyclists (ages 23-29) with maximal aerobic power (VO2max) between 58 and 81 ml.min-1.kg-1 were randomly divided into BRIEF (N = 10) and PROLONGED (N = 10) groups. One hour after drinking a beverage with or without choline bitartrate (2.43 g), cyclists began riding at a power output equivalent to approximately 150% (BRIEF) and 70% (PROLONGED) of VO2max at a cadence of 80-90 rpm. Time to exhaustion, indirect calorimetry and serum choline, lactate, and glucose were measured. Increases in choline levels of 37 and 52% were seen within one hour of ingestion for BRIEF and PROLONGED groups, respectively. Neither group depleted choline during exercise under the choline or placebo conditions. Fatigue times and work performed under either test condition for the BRIEF or PROLONGED groups were similar. Consequently, trained cyclists do not deplete choline during supramaximal brief or prolonged submaximal exercise, nor do they benefit from choline supplementation to delay fatigue under these conditions.

Administration, Oral↗
PubMed1994

State anxiety reduction and exercise: does hemispheric activation reflect such changes?

Acute bouts of aerobic exercise have been consistently associated with significant reductions in anxiety, but explanations for this effect remain elusive. The cerebral lateralization hypothesis predicts that anxiety reductions would be caused by a postexercise decrease in anterior right, relative to left, hemisphere activation. A sample of 19 right-handed males ran at 75% of their VO2max for 30 min on a treadmill. Electroencephalogram (EEG; F3, F4, T3, T4) and state anxiety were collected before and following exercise. Compared with preexercise, anxiety was significantly (P < 0.05) reduced at 10, 20, and 30 min postexercise. Preexercise EEG alpha asymmetry was significantly related to trait anxiety and also predicted a significant amount of variance (30%; P = 0.008) in postexercise anxiety reduction. From pre- to postexercise, the relative activation of the left frontal area increased with respect to the homologous right frontal site. Within-subject correlations for the change in anxiety with corresponding EEG changes were small but in line with theoretical predictions. It is concluded that the cerebral lateralization hypothesis remains tenable for explaining anxiety reductions associated with exercise.

Adult↗
PubMed1993

Electroencephalographic measures of attentional patterns prior to the golf putt.

The purpose of this investigation was to determine the attentional focus patterns associated with golf putting performance. Highly skilled golfers (N = 34) were assessed using electroencephalographic (EEG) measures of the motor and temporal cortices during the 3 s prior to the golf putt. Players completed 40, 12-ft putts and performance was measured in cm error from the hole. Three measures of EEG were analyzed: slow shift, 40 Hz, and relative power spectrum; representing readiness to respond, focused arousal, and general cortical activity, respectively. All three EEG measures suggested a decrease in left hemisphere, motor cortex activity as the player prepared to putt. Relative power measures also showed significant increases in right hemisphere activity in both the motor and temporal cortices. During the last second preceding the putt, increased right hemisphere alpha activity correlated with and predicted less error. Hemispheric differentiation was also reduced as subjects prepared to putt and few, but important, differences existed between the motor and temporal cortices. An important distinction occurred in the alpha band. In the motor cortex left hemisphere alpha increased significantly over time while in the temporal cortex, right hemisphere alpha increased as subjects approached stroke initiation. Differences that existed between the attentional patterns from the present study and past sport studies may relate to the use of one versus two hands to initiate the response.

Adult↗
PubMed1992

The effects of smokeless tobacco on performance and psychophysiological response.

The effects of smokeless tobacco (ST) on psychophysiological response and performance were examined in two studies. Study 1 compared heavy and moderate ST users on psychomotor tasks (simple reaction time/anticipation time and choice reaction time/movement time) in ST (2 g amount) and no smokeless tobacco (NST) conditions. Moderate users performed significantly better than heavy users; there were no significant psychomotor performance differences comparing ST/NST conditions. Heart rate and blood pressure were elevated equally for both groups with the use of ST. Heavy users reported significantly less state anxiety in both ST and NST conditions than moderate users. Study 2 replicated the psychomotor performance results of study 1 when comparing nonusers and ST users who were given four dose amounts of ST (NST, 1/3 mean dose, mean dose, and 5/3 mean) over 4 d. For the math and Stroop tasks, ST use resulted in 12.1% and 10.4% better performance than the NST condition. Physiological measures showed significant elevations during the ST conditions. No differences between dose amounts of ST were apparent for any of the measures. These studies demonstrate that ST users perform better than nonusers when having to react to cognitively challenging task situations.

Adult↗
PubMed1992

Effects of varying doses of smokeless tobacco at rest and during brief, high-intensity exercise.

To determine the influence of varying doses of smokeless tobacco (moist snuff) on resting heart rate and blood pressure and the performance of brief, high-intensity exercise, 12 snuff users were examined at rest and while performing Wingate Anaerobic Tests after taking six different doses of snuff. Snuff caused an increase in heart rate; the larger the dose, the larger the response. Increases in systolic and diastolic blood pressure also occurred but were similar at all doses. Performance of brief, high-intensity exercise was unaffected, so that there was no benefit for such activities (e.g., sprinting bases in base ball).

Adolescent↗
PubMed1991

Does self-efficacy predict performance in experienced weightlifters?

Previous studies that have examined self-efficacy-performance relationships have used novice performers. It is unclear if these findings would generalize to "experienced" performers. Based on Bandura's self-efficacy theory, this study was designed to investigate (a) the effects of false information feedback on self-efficacy beliefs and subsequent weightlifting performance, and (b) whether self-efficacy or past performance is most related to subsequent weightlifting performance. Experienced weightlifters engaged in six performance sessions, each consisting of a one-repetition-maximum bench press. Male subjects (N = 36) were randomly assigned to one of three treatment groups: accurate performance information, false information that they lifted more than their actual lift, or false information that they lifted less than their actual lift. Before each session, subjects indicated the amount of weight they were 100%, 75%, and 50% confident they could lift. Results replicated existing research findings regarding deception and performance; false positive feedback increased future bench press performance. In addition, results indicated that past weightlifting performance accounted for nearly all of the variance in subsequent performance. This finding is discussed in light of the difficulty in extending the predictions of self-efficacy theory to sport settings where athletes have gained experience by undergoing repeated training trials.

Adult↗
PubMed1991

A meta-analysis on the anxiety-reducing effects of acute and chronic exercise. Outcomes and mechanisms.

The relationship between exercise and anxiety has been extensively examined over the last 15 years. Three separate meta-analysis were conducted to quantitatively review the exercise-anxiety literature for state anxiety, trait anxiety and psychophysiological correlates of anxiety. Such a procedure allows tendencies of the research to be characterised. The results substantiate the claim that exercise is associated with reductions in anxiety, but only for aerobic forms of exercise. These effects were generally independent of both subject (i.e. age and health status) and descriptive characteristics. Numerous design characteristics were different, but these differences were not uniform across the 3 meta-analyses. For state anxiety, exercise was associated with reduced anxiety, but had effects similar to other known anxiety-reducing treatments (e.g. relaxation). The trait anxiety meta-analysis revealed that random assignment was important for achieving larger effects when compared to the use of intact groups. Training programmes also need to exceed 10 weeks before significant changes in trait anxiety occur. For psychophysiological correlates, cardiovascular measures of anxiety (e.g. blood pressure, heart rate) yielded significantly smaller effects than did other measures (e.g. EMG, EEG). The only variable that was significant across all 3 meta-analyses was exercise duration. Exercise of at least 21 minutes seems necessary to achieve reductions in state and trait anxiety, but there were variables confounding this relationship. As such, it remains to be seen what the minimum duration is necessary for anxiety reduction. Although exercise offers therapeutic benefits for reducing anxiety without the dangers or costs of drug therapy or psychotherapy, it remains to be determined precisely why exercise is associated with reductions in anxiety. Since several mechanisms may be operating simultaneously, future research should be designed with the idea of testing interactions between these mechanisms.

Acute Disease↗
PubMed1991

The influence of electrocortical biofeedback on performance in pre-elite archers.

The purpose of the present research was to determine whether EEG biofeedback training could improve archery performance as well as self-reported measures of concentration and self-confidence. Experienced pre-elite male (N = 16) and female (N = 8) archers were randomly assigned to one of three treatment conditions: (a) correct feedback (i.e., greater left hemisphere low frequency activity), (b) incorrect feedback (i.e., greater right hemisphere low frequency activity), and (c) no feedback control. The pretest and posttest consisted of 27 shots, with EEG data collected for the left and right temporal hemispheres (T3, T4). Feedback subjects were then given EEG biofeedback, while control subjects rested for 30 min. Analyses indicated that only the performance measure was significant. The correct feedback group significantly improved performance, while the incorrect feedback group showed a significant performance decrement from pre- to posttest (Ps less than 0.05). The control group showed no significant pre-post differences in performance. EEG analyses showed differences that were consistent with the training given to the incorrect, but not the correct, feedback group. Overall, the results provide some support for the use of known relationships between EEG and performance as an effective means of providing biofeedback to affect the performance of pre-elite archers.

Attention↗
PubMed1990

Hemispheric asymmetry, cardiac response, and performance in elite archers.

Previous sport research on elite athletes has shown systematic changes in psychophysiological measures, such as heart rate (HR) deceleration and hemispheric asymmetries in EEG activity, in the few seconds prior to executing a motor response. These changes are believed to be due to a more focused attention on the external environment. Using archery (an attentive state), this investigation was designed to examine: (a) whether hemispheric asymmetry and HR deceleration would occur during the aiming period, and (b) if they did, whether this would affect performance. HR and left and right temporal EEG were recorded from 28 right-handed elite archers for 16 shots. The results indicated that (a) there was no HR deceleration; (b) during the aiming period, EEG alpha activity formed the dominant frequency and this was significantly greater in the left than in the right hemisphere; (c) there were no significant right hemisphere EEG changes in spectral power from 3 s before the shot to arrow release, but there were significant left hemisphere increases at 10, 12, and 24 Hz; and (d) at 1 s prior to the shot, there were no significant right hemisphere spectral power differences between best and worst shots, but there were significant left hemisphere differences at 6, 12, and 28 Hz. The relationships among hemispheric asymmetry, HR deceleration, attentional processes, and shooting performance are discussed.

Adolescent↗
PubMed1987

Cardiac-related cortical activity during variations in mean heart rate.

Koriath and Lindholm (Int. J. Psychophysiol., 1986; 4: 183-195) reported cardiac-related cortical inhibition and speculated that cardiovascular events could modulate electrocortical activity by setting constraints on cortical excitability during diastole based on levels of blood pressure during systole. One dimension of this proposal could be supported if the extent of cardiac-related cortical activity (CRCA) varies with changes in heart rate and blood pressure. The current study investigated this dimension of cardio-cortical relationship by having each subject perform a fixed-foreperiod reaction time task while pedalling a bicycle ergometer under three conditions of workload: No Pedal (0 kpm/min), Lo Pedal (150 kpm/min), and Hi Pedal (450 kpm/min). Mean HR increased significantly from No Pedal to Lo Pedal to Hi Pedal. Results confirmed the presence of CRCA during variations in mean HR and indicated that the extent of CRCA increases with increases in mean HR. This investigation reinforces the importance of the extrahomeostatic effects of cardiovascular afferent fibers and supports the importance of psychophysiological measures which integrate the activity of cardiovascular, autonomic, and central nervous systems.

Adolescent↗