Biomedical subjects

W F Brechue

Publications and source records attributed to W F Brechue.

At least 19 recordsLinked to original sources

PubMed2005

Ageing and midline crossing inhibition.

Age-related deficits of lower extremity lateral movements were investigated to identify a specific age range for the reappearance of midline crossing inhibition (MCI) along a developmental continuum. Ten individuals (five men and five women) representing each decade between the ages of 40 and 89 (five age groups) performed 108 seated trials on a lower extremity apparatus that measured choice reaction time and movement time. Midline crossing inhibition was operationally defined as statistically slower contralateral reaction times when compared to ipsilateral reaction times. The two eldest age groups (70- and 80-year-olds) exhibited MCI only on the first day of testing. Practice may facilitate cross lateral integration in normal ageing adults, even those of advanced age. There were no significant differences for movement times across age groups.

Adult↗

PubMed2003

Chronic clenbuterol administration alters myosin heavy chain composition in standardbred mares.

The purpose of this study was to examine changes in myosin heavy chain (MHC) composition due to chronic clenbuterol administration with or without exercise in mares. Unfit Standardbred mares (aged 10+/-3 years) were divided into four groups: clenbuterol (2.4 micro/kg BW twice daily) plus exercise (3 days/week for 20 min at 50% VO(2max); CLENEX; n=6), clenbuterol only (CLEN; n=6), exercise only (EX; n=5), and control (CON; n=6). Muscle biopsies were obtained from gluteus medius muscle before and after the eight-week training/administration period. MHC composition was determined via SDS gel electrophoresis and quantified using a scanning and densometric system. CLENEX and CLEN exhibited significant (P<0.05) MHC changes while EX and CON did not. MHC type IIA decreased (29.8+/-6.1 to 19.3+/-4.0%, CLENEX; and 36.8+/-12.4 to 26.4+/-7.9%, CLEN) and MHC type IIX increased (59.4+/-7.2 to 71.8+/-5.8%, CLENEX; and 50.5+/-12.5 to 62.0+/-9.3%, CLEN). Chronic clenbuterol administration with and without exercise resulted in a significant shift in MHC profile in Standardbred mares.

Adrenergic beta-Agonists↗

PubMed2002

Comparison of viscoelastic characteristics in triceps surae between Black and White athletes.

The purpose of the present study was to investigate race differences in viscoelastic characteristics of triceps surae muscle group. Black and white college sprint type athletes (n=44) participated in this study. Viscoelastic properties were assessed using the free vibration technique: subjects sat with their forefeet on the edge of a force-plate (Kistler, Switzerland) and support a frame loaded with weights (0-40 kg) on the knees. Oscillations of the triceps surae and Achilles tendon system were initiated with a hand-held hammer by tapping the weight load. Oscillations occur at frequencies of 3-6 Hz and were slightly damped. The damped oscillations in conjunction with the equation of motion of a damped mass-spring model were used to calculate the viscosity of muscle (b), and the elasticity of muscle fibres (k(d)) and tendon (k(t)) in each subject. There were little significant differences in most of physical characteristic variables between black and white athletes. Black athletes have significantly greater muscle viscosity and elasticity than white athletes while tendon elasticity is equivalent. Thus, muscle stiffness is greater among black athletes. Greater muscle stiffness could contribute to greater sprint/jump performance among black athletes, compared with white athletes, through alteration of foot/ground contact and take-off phases during sprinting/jumping.

Achilles Tendon↗

PubMed2002

Relationship between body composition, blood volume and maximal oxygen uptake.

It has long been known that body mass and, more specifically, lean body mass are strongly correlated with maximal oxygen uptake (VO2max) in man and animals. However, there are no data to date describing this phenomenon in the horse. The purpose of this paper is to examine the relationship between body composition and VO2max in the horse. Twenty-three healthy and unfit Standardbred mares performed an incremental exercise test (GXT) to measure VO2max. Rump fat thickness (RTH), a measure of fat covering, was measured using B-mode ultrasound. Plasma volume, total blood volume and red cell volume were determined, using the Evan's Blue dye dilution technique and packed cell volume. VO2max was correlated with body mass (r = 0.541; P<0.01) and exercise haematocrit (exHCT; r = 0.407; P<0.05) but not RTH or the other haematological variables. To eliminate the influence of body mass on the individual variables, a regression analysis was performed on the mass-residuals of VO2max, RTH, plasma volume and exHCT. The residuals of VO2max were correlated negatively with the residuals of RTH (r = -0.687; P = 0.0003) and positively with the residuals of exHCT (r = 0.422; P = 0.045) but not plasma volume. VO2max could be predicted from a linear combination of the residuals of RTH and exHCT (r = 0.767; P<0.0001). These data indicate that VO2max in the horse is significantly related to fat-free mass (FFM), independent of body mass. Red blood cells from the splenic reserve constitute an important factor in the horse's ability to achieve a high VO2max. Therefore, lean body mass may be a more appropriate basis for assessing metabolic function in the athletic horse.

Adipose Tissue↗

PubMed2000

Muscle enlargement in sumo wrestlers includes increased muscle fascicle length.

Skeletal muscle architecture was measured in 28 college sumo wrestlers (Sumo) and 30 control subjects. Pennation angle (PAN) and muscle thickness (MTH) of the triceps long head (TL), vastus lateralis (VL) and gastrocnemius medialis (MG) and lateralis (LG) muscles were measured by B-mode ultrasonography, and fascicle length (FAL) was estimated. Sumo wrestlers had a significantly greater percentage body fat [mean (SD) 33.9 (9.4)%], fat mass [41.7 (18.5) kg], and fat-free mass [76.8 (7.5) kg] than the controls [15.6 (2.5)%, 9.3 (2.4) kg, and 49.9 (6.2) kg, respectively]. MTH was between 18 and 35% greater in sumo wrestlers than in controls. The sumo wrestlers had a significantly greater PAN in the TL, MG and LG muscles than did the controls, but not in the VL. There were significant correlations between PAN and MTH for the sumo wrestlers (r values from 0.33 to 0.57), suggesting that PAN is a function of the relative state of muscle enlargement. FAL was greater (P < 0.01) in the Sumo group for TL (7.26 cm vs 6.13 cm), VL (10.01 cm vs 6.97 cm) and MG (6.41 cm vs 5.53 cm) than in the controls, but not for LG (7.61 cm vs 7.04 cm). Relative FAL correlated significantly with MTH for these muscles in the Sumo group [r values from 0.45 (P < 0.05) to 0.71 (P < 0.01)]. There appear to be architectural differences in the muscle fascicles between sumo wrestlers and controls, with sumo wrestlers having longer fascicles. A greater FAL appears to limit the degree of change in PAN associated with the extreme muscle enlargement seen in sumo wrestlers. This architectural alteration may ultimately improve the expression of the force/cross-sectional area relationship with extreme muscle enlargement.

Adaptation, Physiological↗

PubMed2000

Exercise training in the debilitated aged: strength and functional outcomes.

OBJECTIVE: Resistance and endurance training result in gains in fitness in the aged. It is unclear whether the debilitated elderly can perform moderate-intensity training and whether such training results in short-term improvements in strength, endurance, and function in this population. DESIGN: Randomized, controlled trial. SETTINGS AND PATIENTS: Subjects were from a Veterans Affairs nursing home and rehabilitation unit and a community nursing home. They were older than 60 yrs with impairment in at least one physical activity of daily living. Seventy-eight subjects volunteered and 58 (mean age, 75 yrs; 9 women, 49 men) completed the intervention and initial posttest. Only one subject withdrew because of injury or disinterest. INTERVENTION: Thrice-weekly resistance training (using an isokinetic dynamometer) and twice-weekly endurance training for 4 to 8 weeks. MAIN OUTCOMES: Isometric strength in dominant arm and leg, heart rate response to timed endurance test, and activities of daily living score. RESULTS: The mean change in isometric strength across the muscle movements tested was 32.8% in the training group and 10.2% in the control group (difference, 22.6%; 95% confidence interval, 6.2% to 39.0%). No change in heart rate during exercise was seen in the training group. Trained subjects tended to have a greater improvement in functional activity than control subjects, which was statistically significant (p = .04) for those subjects who at enrollment were most dysfunctional (i.e., activities of daily living score less than 13 [maximum score 26]). CONCLUSION: This group of debilitated elderly patients effectively performed resistance training and increased their strength, with the most impaired gaining the most function. Few in the group could effectively perform endurance training.

Aged↗

PubMed2000

Fascicle length of leg muscles is greater in sprinters than distance runners.

PURPOSE: The purpose of this study was to compare architectural characteristics of leg muscles of sprinters and distance runners. METHODS: Skeletal muscle architectural characteristics were studied in 23 elite male 100-m sprinters (SPR, 10.0-10.9 s for 100 m), 24 elite male distance runners (DR, 13.5-14.5 min for 5000 m), and 24 untrained male controls. Fascicle pennation angle and isolated muscle thickness of the vastus lateralis and gastrocnemius medialis and lateralis muscles were measured in vivo by ultrasound, and fascicle length was estimated. RESULTS: Standing height and upper and lower limb lengths were similar among the groups. Body weight was significantly greater in SPR than in either DR or controls, which were similar. Muscle thickness of the vastus lateralis and gastrocnemius medialis and lateralis muscles was significantly greater in SPR than in either DR or controls, which were similar. In all muscles, pennation angle was similar between SPR and controls, but less than DR. Fascicle length of the vastus lateralis muscle (absolute and relative to limb length) was greatest in SPR and least in DR with control values being between the athlete groups. Fascicle length of the gastrocnemius medialis muscle (absolute and relative to limb length) was greater in SPR than in either DR or controls, which were similar. Fascicle length of the gastrocnemius lateralis muscle (absolute and relative to limb length) was significantly greater in SPR than DR. Absolute fascicle length in gastrocnemius lateralis muscle was similar between DR and controls; however, relative to limb length DR was significantly less. CONCLUSION: Greater fascicle length and lesser pennation angle observed in leg muscles of SPR, compared with DR, would appear to favor shortening velocity as required for greater running speed.

Adult↗

PubMed2000

Sprint performance is related to muscle fascicle length in male 100-m sprinters.

The purpose of this study was to investigate the relationship between muscle fascicle length and sprint running performance in 37 male 100-m sprinters. The sample was divided into two performance groups by the personal-best 100-m time: 10.00-10.90 s (S10; n = 22) and 11.00-11.70 s (S11; n = 15). Muscle thickness and fascicle pennation angle of the vastus lateralis and gastrocnemius medialis and lateralis muscles were measured by B-mode ultrasonography, and fascicle length was estimated. Standing height, body weight, and leg length were similar between groups. Muscle thickness was similar between groups for vastus lateralis and gastrocnemius medialis, but S10 had a significantly greater gastrocnemius lateralis muscle thickness. S10 also had a greater muscle thickness in the upper portion of the thigh, which, given similar limb lengths, demonstrates an altered "muscle shape." Pennation angle was always less in S10 than in S11. In all muscles, S10 had significantly greater fascicle length than did S11, which significantly correlated with 100-m best performance (r values from -0.40 to -0.57). It is concluded that longer fascicle length is associated with greater sprinting performance.

Adult↗

PubMed1999

Architectural characteristics of muscle in black and white college football players.

PURPOSE: The purpose of this study was to determine whether architectural characteristics of skeletal muscle differ by race. METHODS: Skeletal muscle architectural characteristics and body composition were studied in 13 black and 31 white male college football players. Fat-free mass (FFM) and percentage body fat (% fat) were determined by hydrostatic weighing technique. Muscle thickness (MTH) was measured by B-mode ultrasound at 13 anatomical sites. Isolated MTH and muscle pennation angle (PANG) of the triceps long head, vastus lateralis, and gastrocnemius medialis muscles were measured by ultrasound, and fascicle length was estimated. RESULTS: There were no significant differences between blacks and whites in isolated MTH, PANG, and fascicle length in the triceps long head, vastus lateralis, and gastrocnemius medialis muscles. On average, % fat and FFM of black and white football players were 18.8 +/- 4.6% and 17.2 +/- 5.6% for % fat, and 89.9 +/- 15.6 kg and 89.1 +/- 10.4 kg for FFM, respectively. Blacks had a significantly greater, 30%-quadriceps (P < 0.05), 50%-hamstrings (P < 0.05), biceps (P < 0.01), and abdomen (P < 0.01) MTH than those of whites. Standing height and body weight were similar between blacks and whites, but the ratio of leg length to standing height was significantly greater in blacks compared with whites. CONCLUSIONS: It appears that although there may be race differences in anatomical stature, muscle architecture is likely independent of race.

Adult↗

PubMed1998

Plasma volume changes with an acute bout of high-intensity exercise in men with chronic congestive heart failure secondary to coronary artery disease.

We assessed plasma volume changes at peak exercise in 17 nonedematous men with chronic congestive heart failure due to coronary artery disease. Our findings suggest that acute exercise is associated with transient decreases in plasma and blood volume in these patients, similar in magnitude to those reported for healthy adults at peak exercise.

Aged↗

PubMed1998

Gender differences in FFM accumulation and architectural characteristics of muscle.

PURPOSE: The purpose of this study was to gain insight into the skeletal muscle development potential in women and to evaluate the contribution of muscle pennation angle (PANG) and fascicle length to gender differences in muscle size or FFM accumulation. METHODS: Skeletal muscle architectural characteristics and FFM were studied in 29 strength-trained female and 22 age- and height-matched male college athletes. Muscle thickness (MTH) was measured by B-mode ultrasound at 13 anatomical sites. Isolated MTH and PANG of the triceps long head (TL), vastus lateralis (VL), and gastrocnemius medialis (MG) muscles were measured in vivo, and fascicle length was estimated. RESULTS: Six female athletes had more than 60 kg of FFM, with the largest being 82.1 kg. In general, male athletes had a significantly greater FFM and MTH at all sites except for the anterior thigh. Isolated MTH and PANG of the TL, VL, and MG were greater in males. There were no gender differences in limb length or fascicle length of the three isolated muscles. A significant correlation was observed between MTH and PANG for TL (r = 0.84) and MG (r = 0.41), but not for VL. CONCLUSIONS: In contrast to previous estimates, we conclude that the theoretical upper limit of FFM accumulation and FFM-to-height ratio in women is greater than 80 kg and 0.44 kg.cm-1, respectively. Gender differences in PANG appear to be related to differences in muscle size (MTH) and do not appear to contribute independently to the gender difference in FFM.

Adipose Tissue↗

PubMed1998

Mechanical and metabolic determination of VO2 and fatigue during repetitive isometric contractions in situ.

Repetitive isometric tetanic contractions (1/s) of the canine gastrocnemius-plantaris muscle were studied either at optimal length (Lo) or short length (Ls; approximately 0.9 . Lo), to determine the effects of initial length on mechanical and metabolic performance in situ. Respective averages of mechanical and metabolic variables were (Lo vs. Ls, all P < 0.05) passive tension (preload) = 55 vs. 6 g/g, maximal active tetanic tension (Po) = 544 vs. 174 (0.38 . Po) g/g, maximal blood flow (Q) = 2.0 vs. 1.4 ml . min-1 . g-1, and maximal oxygen uptake (VO2) = 12 vs. 9 micromol . min-1 . g-1. Tension at Lo decreased to 0.64 . Po over 20 min of repetitive contractions, demonstrating fatigue; there were no significant changes in tension at Ls. In separate muscles contracting at Lo, Q was set to that measured at Ls (1.1 ml . min-1 . g-1), resulting in decreased VO2 (7 micromol . min-1 . g-1), and rapid fatigue, to 0.44 . Po. These data demonstrate that 1) muscles at Lo have higher Q and VO2 values than those at Ls; 2) fatigue occurs at Lo with high VO2, adjusting metabolic demand (tension output) to match supply; and 3) the lack of fatigue at Ls with lower tension, Q, and VO2 suggests adequate matching of metabolic demand, set low by short muscle length, with supply optimized by low preload. These differences in tension and VO2 between Lo and Ls groups indicate that muscles contracting isometrically at initial lengths shorter than Lo are working under submaximal conditions.

Animals↗

PubMed1997

Acetazolamide reduces peripheral afferent transmission in humans.

Carbonic anhydrase has been localized in skeletal muscle and nerve, thus, inhibition with acetazolamide (ACZ) may alter nerve and/or muscle function in healthy humans. ACZ (3 oral doses 14, 8, and 2 h prior to testing) reduced isometric force (37%) and peak to peak electromyographic (EMG) amplitude (1.38 mV to 0.83 mV), while increasing EMG latency associated with a unilateral Achilles tendon-tap. Reflex recovery profiles, following a contralateral conditioning tap, were similar in both placebo and ACZ experiments. ACZ led to significant changes in Hmax/Mmax ratio (52.19/14.42 to 45.73/15.65) and H-reflex latency (34.18 +/- 2.54 ms to 35.24 +/- 2.74 ms). Motor nerve conduction velocity and maximal voluntary isometric torque (knee extensors) were unaltered by ACZ. These data suggest that inhibition of the tendon-tap reflex and associated isometric force, following ACZ, is related to impairment of synaptic integrity between la fibers of the muscle spindle and the alpha motor neuron and not impairment of the muscle spindle or force-generating capacity.

Acetazolamide↗

PubMed1996

Effect of resistance training volume on strength and muscle thickness.

The purpose of this study was to determine the effects of different volumes of high-intensity resistance training on isometric torque and muscle thickness. Training was conducted three times per week using one set (low volume, EX-1, N = 18) or three sets (high volume, EX-3, N = 20) of dynamic variable resistance exercise. Ten subjects acted as nontraining controls (CONT). Bilateral knee extension (KEXT) and flexion (KFLEX) exercise was performed to fatigue within 8-12 repetitions for 14 wk. Maximal isometric KEXT and KFLEX torque was tested at 6 degrees, 24 degrees, 42 degrees, 60 degrees, 78 degrees, 96 degrees, and 108 degrees of KFLEX using a MedX (Ocala, FL) KEXT/KFLEX ergometer. The anterior (ANT), lateral (LAT), and posterior (POST) right thigh, the medialis muscle (MED), and the lateralis muscle (LATER) were assessed for thickness by B-mode ultrasound (ULTRA). Both training groups improved torque output at most angles, but there was no difference between EX-1 and EX-3 (P > or = 0.05). ULTRA detected increases in muscle thickness for EX-1 at 60% LAT and 40% and 60% POST. EX-3 increased muscle thickness at the MED, and 40% and 60% POST. In conclusion, one set of high intensity resistance training was as effective as three sets for increasing KEXT and KFLEX isometric torque and muscle thickness in previously untrained adults.

Adolescent↗

PubMed1996

Exercise training for coronary artery disease in the elderly.

Treatment of the elderly cardiac patient poses a unique problem to the clinician. In addition to cardiovascular symptoms related to coronary artery disease, age-related decrements in health, and physical function associated with musculoskeletal decline must also be addressed. Exercise training/physical activity has been shown to have a positive impact on health and function in primary and secondary prevention in young and elderly clinical populations. Although the components of and guidelines for prescribing an exercise program are similar for younger and older cardiac patients, the principles should be applied to meet the unique goals and demands of the elderly cardiac patient.

Aged↗

PubMed1995

Blood flow and pressure relationships which determine VO2max.

The role of O2 delivery in regulating VO2max has been studied in an isolated gastrocnemius-plantaris muscle preparation contracting in situ; recent data addressing this issue are presented. VO2 increases nonlinearly with stimulation frequency reaching a peak at 5 twitches.s-1 or 1 tet.s-1 (200 ms trains, 50 imp.s-1). Further increases in stimulation frequency result in a lower VO2. Measured VO2 maxima are less than predicted VO2 capacity, and peak VO2 during tetanic contractions is greater than that during twitches. Above 150 imp.min-1, VO2 is directly related to the level of blood flow attained as VO2/Q (arterial-venous O2 difference) is fixed by some unknown mechanism. Increasing blood flow, with a pump, during 1.s-1 tetanic contractions increases O2 diffusive conductance and peak VO2. When O2 delivery is reduced, ischemic hypoxia appears to result in more rapid reductions in muscle performance than hypoxic hypoxia because of decreases in perfusion pressure and Q. 31P-NMR studies reveal that reductions in creatine phosphate and energy charge are similar between ischemia and hypoxia suggesting a common regulator, O2. We conclude that VO2max is limited by O2 delivery as a result of a limited and uneven distribution of muscle blood flow. These limitations appear secondary to mechanical restraints imposed by contraction duty cycle and vascular compression.

Animals↗

PubMed1995

Muscle blood flow and distribution determine maximal VO2 of contracting muscle.

During repetitive contractions, the VO2 of the dog gastrocnemius-plantaris muscle rose with the contraction frequency up to a maximal value and then decreased as contraction frequency was increased further. PVO2 was constant over most of the contraction frequency range. Reducing perfusion pressure/blood flow reduced VO2max with a constant PVO2. During these maneuvers the diffusion conductance, DCO2 (VO2/PVO2), changed with VO2. Raising the perfusion pressure/flow with a pump increased VO2 with a small rise in PVO2 so that DCO2 also increased. Removing tension from the muscle between contractions elevated VO2 and DCO2 without a change in perfusion pressure. Hypoxemia decreased VO2 with a decrease in PVO2; DCO2 remained constant. A three-compartment mathematical model, based on microsphere measurements of regional flow, was used to illustrate how regional flow variations may exist, and how they are poorly revealed in the mixed whole-muscle venous blood. The model shows VO2.g-1 strongly related to flow. As VO2.g-1 increased as Q.g-1 increased, extraction decreased, and DCO2 increased.

Animals↗

PubMed1994

Lactate and acid-base exchange during brief intense contractions of skeletal muscle in situ.

Our goal was to design a stimulation-contraction paradigm using an isolated in situ dog gastrocnemius muscle preparation that would provide an experimental model for brief intense intermittent (IC) exercise in humans. Second, acid-base and ion exchanges across the muscle were investigated using four 30-s bouts of isotonic tetanic contractions (2 s-1, 100-ms train, 50 impulses/s) with 4 min of rest between bouts. During the bouts, peak power output (W) was 18.2 mW/g in the first bout; it declined by 4.4% by the fourth bout and by 12-16% in each bout. Compared with repetitive continuous contractions (CC) at maximal O2 uptake (VO2), W was greater and VO2 (approximately 3.5 mumol.g-1.min-1) and CO2 production (approximately 4.5 mumol.g-1.min-1) were less with IC. Venous-arterial (v-a) differences and lactate output peaked immediately after each bout and were not different from the values reported for CC at maximal VO2. Thus, with IC, VO2/W was lower and the CO2 production/VO2 and lactate output/VO2 ratios were greater than those seen with CC. These differences suggest that this stimulation-contraction paradigm may be an appropriate model for brief intense exercise. The v-a [H+] difference was a direct result of the v-a PCO2 difference. The venous strong ion difference was always greater than or equal to the arterial strong ion difference because the v-a [Cl-] difference was opposite and greater than the v-a lactate concentration difference, whereas the v-a [Na+] and [K+] differences were small.(ABSTRACT TRUNCATED AT 250 WORDS)

Acid-Base Equilibrium↗