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Biomedical subjects

H N Williford

Publications and source records attributed to H N Williford.

At least 19 recordsLinked to original sources
PubMed2004

Physiologic profile of recreational male and female novice and experienced Tae Kwon Do practitioners.

AIM: Subjects, 28 recreational male and female novice and experienced Tae Kwon Do practitioners (age 19-42 years), were examined on 6 physiological parameters: body composition (BF%, skinfold measures), flexibility (sit-and-reach and leg-splits tests), lower and upper-body dynamic muscular strength (leg press and bench press), abdominal strength and endurance (1-minute timed, bent-knee sit-ups test), lower extremity explosive power (vertical jump-and-reach test), and cardiovascular endurance (graded exercise treadmill test). METHODS: Subjects were assigned to 1 of the 4 following groups: Tae Kwon Do experienced and trained men (MT), Tae Kwon Do experienced and trained women (FT), novice Tae Kwon Do men (MN), and novice Tae Kwon Do women (FN). RESULTS: Results of multiple testing procedures and comparison across groups indicated that Tae Kwon Do black belts were more athletically fit as compared with that of novice Tae Kwon Do practitioners of the same sex in spite of the fact that male and female black belts were older than their novice counterparts. Experienced Tae Kwon Do subjects were stronger as measured by lower body strength and showed better aerobic performance capacity as well as lower percent body fat. Additionally, MT subjects demonstrated higher flexibility. CONCLUSION: The highly diverse training, repeated and continuous use of the legs and arms alone or combined with maximal stretching, and high intensity exercise may account for observed differences among groups.

Adaptation, Physiological↗
PubMed1999

Relationship between fire fighting suppression tasks and physical fitness.

This investigation evaluated the relationship between physical fitness and performance of fire suppression tasks. The following mean +/- SD values were associated with 91 fire fighters: age 31.69 +/- 7.39 years, height 177.29 +/- 6.38 cm, weight 83.97 +/- 10.86 kg, % fat 13.78 +/- 4.31, fat free weight (FFW) 71.52 +/- 7.66 kg, pull-ups 9.03 +/- 4.79, push-ups 41.02 +/- 14.08, 1.5 mile run 737.60 +/- 108.11 s, sit and reach 32.00 +/- 8.5 cm, sit-ups 39.88 +/- 7.75, and total grip strength 116.75 +/- 17.67 kg. The physical performance assessment (PPA) consisted of the following: stair climb, hoist, forcible entry, hose advance, and victim rescue. Significant correlations (p < 0.01) were found between the PPA and the following: total grip strength (r = -0.54), FFW (r = -0.47), height (r = -0.40), pull-ups (r = -0.38), push-ups (r = -0.38), 1.5 mile run (r = 0.38), sit-ups (r = -0.32), weight (r = -0.30) and % fat (r = 0.30). Multiple regression analysis indicated that the best multiple predictor of PPA was the 1.5 mile run, FFW, and pull-ups, r = 0.73, p < 0.001. This investigation shows the importance of physical fitness as related to performance of fire suppression job tasks.

Adult↗
PubMed1998

Voice problems and risk factors among aerobics instructors.

Fifty female and four male aerobics instructors completed a questionnaire pertaining to vocal problems and variables that could indicate an increased risk for developing problems. The questions concerned teaching experience, physical data regarding instructional facilities, method of voice projection, music volume, history of illness, allergies, voice loss, hoarseness, smoking habits, and knowledge of vocal hygiene. The results showed that a significant number of instructors experienced partial or complete voice loss (44%) during and after instructing, as well as increased episodes of voice loss, hoarseness, and sore throat unrelated to illness since they began instructing. Significant variables associated with voice problems included sore throat and hoarseness following instruction, and shouting to cue the participants. It was also found that very few instructors in this study had any knowledge of vocal hygiene techniques.

Adult↗
PubMed1998

Cardiovascular and metabolic costs of forward, backward, and lateral motion.

PURPOSE: The purpose of this study was to compare the metabolic and cardiovascular responses of movement in forward (FM), backward (BM), and lateral (LM) directions. METHODS: Thirteen athletes with the following characteristics (mean +/- SD) were evaluated: age 21+/-3 yr, height 172.0+/-9.0 cm, weight 62.92+/-9.05 kg, and VO2max 54.13+/-7.42 mL x kg(-1) x min(-1). Subjects were evaluated at 80.45 and 134.08 m x min(-1). A repeated measures ANOVA was used for statistical analysis (P < 0.05). RESULTS: At 80.45 m x min(-1), the following respective VO2 mL x kg(-1) x min(-1) and heart rate (HR) beats x min(-1) responses were: FM = 12.42+/-2.29, 113+/-10; BM = 15.95+/-2.45, 132+/-16; and LM = 22.10+/-4.76, 140+/-15. Both VO2 and HR were significantly different between conditions: LM > BM > FM. At 134.08 m x min(-1), the following respective VO2 and HR responses were: FM = 27.15+/-2.51, 146+/-7; BM = 31.33+/-5.77, 168+/-11; and LM = 32.58+/-5.74, 169+/-10. At 134.08 m x min(-1) neither HR or VO2 were significantly different between LM or BM (LM, BM, > FM). Stride length and stride frequency were also significantly different between conditions. These results indicate the variation in the energy cost of FM, BM, and LM.

Adult↗
PubMed1998

Bench stepping and running in women. Changes in fitness and injury status.

BACKGROUND: The purpose of this investigation was to evaluate injury rates and changes in VO2peak in women associated with aerobic exercise (bench stepping and running). METHODS: A pretest post-test repeated measures design was used to evaluate changes in VO2peak after training for 10 weeks, 3 days per week, for 1 hour per session. Injury incidence was monitored by questionnaires throughout the training program. SETTING: All testing and training took place at Auburn University Montgomery, Montgomery, AL, USA. PARTICIPANTS: The subjects were women enrolled in university physical activity courses. The exercise groups consisted of 23 women who performed bench exercise and 15 who performed running-jogging. Eleven subjects served as non-exercising controls. INTERVENTION: The 10-week exercise training program served as the intervention. MEASURES: Subjects were both pre- and post-tested for VO2peak by open circuit calorimetry. Body composition was estimated from a 7-site skinfold equation. A daily injury log was maintained to evaluate injury status. RESULTS: A repeated measures ANOVA found similar significant improvements in VO2peak for both the bench and running groups with no change for the control group. An evaluation of the injuries graded II or higher found 0.29 injuries per 100 hrs for the bench group and 0.66 injuries per 100 hrs for the running group. When all complaints were considered (grade I to grade IV) the rates increased to 2.44 per 100 hrs for the running group and 6.09 per 100 hrs for the bench group. CONCLUSIONS: Aerobic bench exercise produced similar changes in VO2peak compared to running. The results indicated that the primary injury complaints were grade I and related to delayed onset muscle soreness (DOMS). The bench group experienced an greater incidence of grade I complaints while the running group experienced a slightly greater incidence of more serious grade II or higher injuries.

Adult↗
PubMed1998

Effects of exercise training on aerobic fitness in African-American females.

Physical inactivity, a primary risk factor for cardiovascular disease, is more prevalent within the African-American population. Unfortunately, only a few investigators have documented the effects of exercise training studies on cardiovascular fitness in this cohort. Therefore, the purpose of this study was to examine the effects of a six-week endurance exercise training program on aerobic fitness (VO2peak) in African-American females. Twenty-five women (16 treatment, 9 controls, mean age 23.1+/-3.9) participated in the study. The six-week exercise training protocol consisted of exercising three times a week on a cycle ergometer between 60-70% VO2peak for 20 minutes. No significant changes in aerobic fitness were observed in the control group. However, the relative and absolute VO2peak significantly increased by 18% and 19%, respectively, in the treatment group, 21.7+/-2.6 to 25.6+/-2.8 mL x kg(-1) x min(-1) (P<.01) and 1.77+/-2.7 to 2.11+/-3.8 L x min(-1) (P<.01). The maximal heart rates and respiratory exchange ratios were not significantly different between pre- and post-training, suggesting that similar efforts were given. These results document the fact that significant increases in aerobic fitness are possible with a moderate exercise training regime in an African-American female population.

Adult↗
PubMed1997

Vertical impact forces during bench-step aerobics: exercise rate and experience.

The purpose of this study was to determine the effects of two bench-step exercise speeds on vertical impact forces and to explore this variable between novices, and instructors. 12 women (mean age 24 yr.) randomly performed 8-min. protocols of the "basic" bench-stepping technique and a more advanced "travel" technique at 30 and 33 cycles.min.-1. Analysis showed that the faster exercise rate yielded significantly higher vertical impact forces on a reference (B-8) step height (20.3 cm). At 33 cycles.min.-1, the instructors, and novices' responses were both higher than those at 30 cycles.min.-1. The mean peak vertical impact force ranged from 1.54 times the body weight for the novice group at 30 cycles.min.-1 to 1.87 times the body weight for instructors at 33 cycles.min.-1. A comparison of the groups' force curves showed a distinctive pattern in the loading of the impact forces. Specifically, the instructors consistently produced a transitory decrement in force prior to attaining peak force. In addition, the novices exhibited nonuniform increases in the production of vertical impact force across other step heights at the faster (33 cycles.min.-1) speed. Thus, experience with bench-step exercise may afford an ability to make uniform and force-absorbing adjustments in the resultant vertical impact forces at increased speeds.

Adult↗
PubMed1996

Injury rates and physiological changes associated with lateral motion training in females.

The purpose of this investigation was to evaluate physiological changes and injury rates associated with lateral motion (slideboard) training. Twenty-five females performed slideboard exercise 3 days per week, 1 hour each session, over a 10 week period. Eleven females served as controls. The subjects were pre and post tested via treadmill exercise to determine VO2peak. Body composition was analyzed by a seven-site skinfold equation. The slideboard subjects (SBS) were evaluated daily for injury incidence. A factorial repeated measures ANOVA (p < 0.05) revealed a significant 14% increase in VO2peak. No significant modifications were shown for body composition. The incidence of injury was 80% for Grade I injuries, 52% for Grade II injuries, 0% for Grade III injuries, and 4% for Grade IV injuries. Thus, the primary injury reports were of a Grade I and Grade II level of severity. The present injuries were largely associated with delayed onset muscle soreness (DOMS) in the medial leg musculature during the first two weeks of training. These results show that during a 10 wk training program lateral motion exercise is an effective mode for improving cardiorespiratory fitness. In addition, the risk of incurring an injury requiring medical attention appears to be quite low. However, untrained women who perform this activity at a frequency, duration, and intensity similar to the present study may experience muscle soreness during the initial period of training.

Adult↗
PubMed1996

Cross-validation of non-exercise predictions of VO2peak in women.

The purpose of this investigation was to cross-validate non-exercise (N-Ex %fat and N-Ex BMI) models for predicting VO2peak in females, and to evaluate the validity of these models in estimating fitness status, based on a < 9 METs cardiovascular fitness/health-risk criterion. Subjects were 165 females who completed the PA-R activity scale and were evaluated for VO2peak and body composition. The cross-validation statistics for the N-Ex %fat and N-Ex BMI models were: ryy' = 0.86, E = 6.3 (ml.kg-1.min-1), and ryy' = 0.81, E = 6.9 (ml.kg-1.min-1), respectively. Both models were found to accurately identify 87% of the subjects with VO2peak < 9 METs. The statistics associated with the < 9 MET criterion were: ryy' = 0.73, E = 3.4 (ml.kg-1.min-1), and ryy' = 0.80, E = 4.5 (ml.kg-1.min-1), for N-Ex %fat and N-Ex BMI, respectively. The N-Ex models yielded values similar to those reported previously (Jackson, A. S., S. N. Blair, M. T. Mahar, L. T. Wier, R. M. Ross, and J. E. Stuteville. Prediction of functional aerobic capacity without exercise testing. Med. Sci. Sports Exerc. 22:863-870, 1990). When exercise testing is not an option, the present N-Ex models provide an alternative method for predicting VO2peak in females.

Adolescent↗
PubMed1996

The physiological effects of bench/step exercise.

Recent investigation of acute cardiorespiratory responses to the current 'popularised' style of bench/step exercise has validated its use in improving aerobic physical fitness, particularly in women. However, no marked differences in relative measures of cardiorespiratory demand have been reported between men and women. Instructor data and training investigations further substantiate the effectiveness of bench/step exercise in promoting physical fitness, including upper body strength. However, the energy cost of bench/step exercise can vary dramatically. Important factors include, the selected step height, exercise rate, imposed step manoeuvre, routine format and use of hand-held weights. Hand-held weights may be more useful for men than woman. During training, bench/step exercise has been reported to yield a high incidence of grade I injury complaints, particularly in the calf and shoulder region. However, nearly 90% of these complaints were attributable to acute muscle soreness. Few serious injuries have been associated with the activity. Biomechanical research has shown that the ground reaction forces (GRF) experienced during bench stepping are lower than running and directly related to the step height and type of manoeuvre. In addition, compared with novices, instructors exhibit a moderation in the GRF pattern generated during landing. This suggests that a learning effect has occurred and that teachers yield a more consistent landing pattern. Finally, the activity may be effective in improving body composition, but a consideration of factors related to energy expenditure (e.g. exercise duration and dietary control) appear to be important in regimens prescribed for modifying body fat.

Athletic Injuries↗
PubMed1996

Self-reports on the Eating Disorder Inventory by female aerobic instructors.

This study examined the possibility of eating disorders in 30 female aerobic dance instructors. All subjects completed a biographical questionnaire and the Eating Disorder Inventory. The results showed that the aerobic instructors yielded scores which were comparable to similarly aged female weight lifters but tended to be lower than those of women distance runners (also of similar age). Interestingly, 23% (n = 7) of the subjects reported a previous history of bulimia and 17% (n = 5) reported a previous history of anorexia. Thus, 40% of the instructors indicated a previous experience with eating disorders. Based on all 30 participants, the mean scores associated with Body Dissatisfaction, Drive for Thinness, Ineffectiveness, and Perfectionism were quite comparable to those previously established for anorexic groups. In addition, a relatively high percentage of the sample yielded scores which were actually greater than mean values associated with anorexia patients on nine of the 11 subscales. Based on these results, a number of the aerobic dance instructors possessed scores suggesting behaviors and attitudes consistent with female athletes whose sports emphasize leanness and comparable to those who have eating disorders.

Adult↗
PubMed1996

Hemodynamic responses to cold stress in blacks: effect of application site.

Black Americans have been shown to exhibit increased blood pressure responses to a variety of physical stressors. However, few investigators have examined hemodynamic responses to cold stress. Additionally, no studies have compared blood pressure responses to forehead and foot stress in blacks. Therefore, in this study, hemodynamic responses to cold pressor tests were compared in 30 blacks (15 males, 15 females) utilizing two application sites. Baseline comparisons of systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate (HR), forearm blood flow (FBF) and forearm vascular resistance (FVR) were not different prior to forehead and foot cold stress. Following baseline measurements, ice was applied separately to the forehead and foot for 90 seconds with hemodynamic measurements being recorded at 45 and 90 seconds. During application of ice to the forehead, FVR-90 was significantly higher (P < .002, 97.0 units vs. 66.4 units) compared to the foot. The application of ice to the foot resulted in significantly greater SBP-45 responses (P < .0001, 147 mmHg vs. 139 mmHg), HR-45 responses (P < .0043, 80, b.min-1 vs. 69 b.min-1). HR-90 responses (P < .0001, 78 b.min-1 vs. 64 b.min-1), and FBF-45 responses (P < .05, 2.74 ml.min-1.100ml-1 vs. 1.98 ml.min-1.100ml-1). These findings suggest that blacks exhibit disparate patterns of reactivity in response to cold stress as a function of application site. Therefore, investigators should consider the application site when interpreting studies examining a biracial cohort.

Adult↗
PubMed1996

Exercise training in black adolescents: changes in blood lipids and Vo2max.

The purpose of this investigation was to evaluate the effects of a 15-week exercise training program on cardiovascular and blood lipid variables in black adolescents. Subjects consisted of black males with 12 of these participating in an exercise conditioning program and 5 designated as the control group participating in a team sports program. The mean +/- SD age was 12.8 +/- 0.97 yrs. Training for the exercise group was conducted 5 d.wk-1 for 15 weeks (weight training 2 d.wk-1 and aerobic training 3 d.wk-1). The following mean +/- SD significant changes were found for pre- to post-training for the exercise group (P < 0.05) with no significant change for controls: high density lipoprotein cholesterol (HDL-C) 1.11 +/- 0.18 to 1.28 +/- 0.17 (mmol.l-1), low density lipoprotein cholesterol (LDL-C) 2.73 +/- 0.74 to 2.41 +/- 0.81 (mmol.l-1), maximal oxygen uptake (VO2max) 43.7 +/- 9.4 to 48.2 +/- 9.7 (ml.kg-1.min-1), and maximal ventilation (VE max) 70.59 +/- 16.8 to 80.93 +/- 14.6 (L.min-1). In addition, no significant changes were found for blood pressure or other blood lipid parameters for either group. Results of this study show that exercise training can favorably alter blood lipid and VO2max values. Therefore, a vigorous exercise training program for young black males can favorably affect their cardiovascular risk profile.

Adolescent↗
PubMed1995

The metabolic responses of slideboard exercise in females.

Recently, slideboard exercise training has been introduced as a mode of aerobic training. The purpose of the investigation was to determine the acute cardiovascular and metabolic responses to slideboard exercise. Subjects consisted of 20 healthy females with a mean age of 26.5 +/- 7.9 years, and a VO2max of 40.8 +/- 5.6 ml.kg-1.min-1. The results of the investigation showed that 10 min of a commercially produced slideboard routine elicited mean heart rate (HR) responses ranging from 160 to 168 beats.min-1 and VO2 values of 27.5 to 33.5 ml.kg-1.min-1. A sub-group of 10 subjects was also evaluated while performing sliding exercise at different sliding rates (SR). Subjects performed the standard slide technique at metronome cadences of SR-40, SR-50, and SR-60 slide.min-1. As sliding rate increased so did HR and VO2. The subjects demonstrated mean responses of approximately 55 to 81% of VO2max for the slower to the most rapid sliding rates, respectively. Compared to treadmill exercise at the same oxygen consumption levels, the heart rates for sliding were approximately 15% higher. Slideboard exercise can be an alternative mode of aerobic training.

Adult↗
PubMed1995

A test to estimate VO2max in females using aerobic dance, heart rate, BMI, and age.

OBJECTIVE: The purpose of this investigation was to develop a sub-maximal exercise test for estimating VO2max utilizing aerobic dance. EXPERIMENTAL DESIGN: One hundred females between the ages 18 to 40 yr served as the subjects for test validation. The subjects completed a treadmill test to determine VO2max and were assessed for heart rate (HR) response to a bout of aerobic dance. The data associated with responses to treadmill exercise and the aerobic dance test, in conjunction with descriptive variables (e.g., age, BMI) were utilized in the validation of the multiple regression model. MEASURES: Reliability was determined by correlation and paired "t"-tests of the aerobic dance routine test and retest trials. The construction of the multiple regression equation, via forward entry analysis, and the cross-validation of the regression equation were completed to ensure the validity and reliability of the protocol in accurately estimating VO2max. RESULTS: Test, retest reliability for the dance-exercise routine was demonstrated (r = 0.98). Moreover, no significant differences were shown between the HR responses for the test and retest trials. The multiple regression analysis yielded a three variable multiple prediction equation for estimating VO2max (R = 0.84; SEE, 5.5 ml.kg-1.min-1). The three variables were the HR response to four min of aerobic dance (HR4), body mass index (BMI), and age (years). Cross-validation of the aerobic dance test was determined with a second group of 50 female subjects (R = 0.83; SEE, 5.5 ml.kg-1.min-1). Additionally, the application of the validation group regression equation to the cross-validation group yielded a comparable R of 0.82. Comparison of the predicted values for VO2max from both equations also yielded a highly significant invariance coefficient of 0.96. Finally, the results of "t"-tests between the observed and predicted mean values for VO2max revealed no significant difference (p > 0.05). Therefore, the final prediction equation, based on collapsing the means associated with the validation and cross validation samples (n = 150), was: VO2max (ml.kg-1.min-1) = 130.18-(0.38 * HR4)-(0.81 * BMI)-(0.27 * Age); R = 0.84, SEE = 5.5 ml.kg-1.min-1. CONCLUSIONS: These results indicate that a four minute aerobic dance test provides a valid and reliable sub-maximal protocol for estimating VO2max and providing an index of aerobic fitness in apparently healthy 18 to 40 yr old females.

Adolescent↗
PubMed1994

The prediction of fitness levels of United States Air Force officers: validation of cycle ergometry.

The purpose of this investigation was to evaluate the accuracy of the United States Air Force cycle ergometer test (CET) to predict maximal oxygen uptake (VO2max) of Air Force officers. The United States Air Force is currently evaluating cardiovascular fitness by cycle ergometry. In order to validate the accuracy of the CET, 50 male Air Force officers who were attending professional military education at Maxwell AFB were evaluated by a maximal treadmill Bruce test and open circuit spirometry. Characteristics of the subjects included the following mean values +/- SD: VO2max = 47.9 +/- 10.3 ml.kg-1.minute-1; age = 39.3 +/- 3.9 years; weight = 76.9 +/- 9.5 kg; height = 176.4 +/- 8.8 cm; percent fat = 20 +/- 9%; heart rate max = 174 +/- 10 beats.minute-1; and respiratory exchange ratio = 1.09 +/- 0.09. The predicted VO2max with the cycle ergometer test was 39.9 +/- 9.8 ml.kg-1.minute-1. The following product-moment correlation was derived between criterion VO2max (maximal treadmill test and the CET: r = 0.74 and standard error of estimate = 6.9 ml.kg-1.minute-1). A repeated measures analysis of variance between the CET and maximal treadmill test found a significant mean difference of 8.0 ml.kg-1.minute-1 (p < 0.0001). The CET significantly underpredicted fitness levels of Air Force officers. Based upon Air Force standards, the CET underpredicted oxygen uptake values by approximately one fitness category or 17%.

Adult↗
PubMed1993

Iron status in women aerobic dance instructors.

This investigation evaluated the iron and nutritional status of 12 highly trained aerobic dance instructors who did not take iron supplements (ANS) and 8 who did (AS). A control group (C) consisted of 10 age matched controls. The aerobic instructors had exercised for approximately 3.8 days/wk, 56 min/session for the past 7 yrs. There were no significant differences among groups for energy intake, carbohydrate, protein, fat, nonheme iron, heme iron, or total iron intake (excluding supplemental iron). But both exercise groups had lower ferritin values than the control group. There was also a significant difference in mean cell volume (MCV), with both exercise groups having greater values than the control group. There were no differences among groups for serum iron, total iron binding capacity, transferrin saturation, hematocrit, or hemoglobin. One in three aerobic dance instructors had serum ferritin values below 12 micrograms.L-1. Results indicate that women exercise leaders have iron profiles that are similar to other groups of female athletes. The increased MCV values suggest runners' macrocytosis or an exercise induced macrocytosis.

Adult↗