摘要:

The case history of an elite ultra-endurance cyclist who developed chronic fatigue syndrome.Med. Sci. Sports Exerc.,Vol. 30, No. 9, pp. 1345-1348, 1998. An elite ultra-endurance athlete, who had previously undergone physiological and performance testing, developed chronic fatigue syndrome (CFS). An incremental cycling exercise test conducted while he was suffering from CFS indicated decreases in maximum workload achieved (Wmax;−11.3%), the maximum oxygen uptake (V˙O2max; −12.5%), and the anaerobic threshold (AT; −14.3%) compared to pre-CFS data. A third test conducted after the athlete had shown indications of significant improvement in his clinical condition revealed further decreases in Wmax(−7.9%), V˙O2max(−10.2%) and AT (−8.3%). These data, along with submaximal exercise data and muscle biopsy electron microscopic analyses, suggest that the performance decrements were the result of detraining, rather than an impairment of aerobic metabolism due to CFSper se.These data may be indicative of central, possibly neurological, factors influencing fatigue perception in CFS sufferers.

ISSN:0195-9131    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Phonophoresis versus ultrasound in the treatment of common musculoskeletal conditions.Med. Sci. Sports Exerc.,Vol. 30, No. 9, pp. 1349-1355, 1998.Purpose:The purpose of this study was to determine whether the pain response after phonophoresis(PH) differs from the pain response after ultrasound (US) alone.Methods:Forty-nine subjects with soft tissue injuries including epicondylitis, tendinitis, and tenosynovitis were randomly assigned (double blinded technique) to PH or US treatment groups. Both groups received 8 min of continuous US at 1.5 w·cm−2, three times per week for 3 wk. For the PH group a gel containing 0.05% fluocinonide was used as a coupling agent. An identical gel absent the steroid was used for the US group. Subjects indicated their pain level by marking on a visual analog scale (VAS) at the start of treatment and at the end of weeks 1, 2, and 3. Pressure algometry was used to note tolerance to direct pressure over the target tissue. ANOVA for repeated measures was used to analyze data.Results:At the end of 3 wk of treatment, both groups combined showed a significant decrease in pain level and an increase in pressure tolerance (P< 0.05), but there were no differences between groups from the onset of treatment to the end of week 3 (VAS: US 5.5-1.9, PH 5.0-2.0; algometry (involved limb): US 4.7 lb-7.1 lb, PH 5.1 lb-6.6 lb).Conclusions:We conclude that US results in decreased pain and increased pressure tolerance in these selected soft tissue injuries. The addition of PH with fluocinonide does not augment the benefits of US used alone.

ISSN:0195-9131    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Spectral analysis of electroencephalography changes after choking in judo (juji-jime).Med. Sci. Sports Exerc.,Vol. 30, No. 9, pp. 1356-1362, 1998.Purpose:The present study was carried out to investigate possible electroencephalographic changes induced by choking in judo (shime-waza) by means of spectral analysis and brain mapping.Methods:Power spectral changes in Electroencephalography (EEG) were recorded in six experienced judoka who underwent a choking trial with a "shime-waza choking" technique called juji-jime.Results:A significant increase of global field power in the delta- and theta-range occurred, while physiological alpha-power decreased. These changes in the low-frequency range reached a statistically significant level within a time span up to 20 s after choking, which was performed at an average choking time of 8 s. In no case did choking provoke neuropsychological symptoms. Yet, spectral EEG-analysis revealed subclinical changes of brain function.Conclusions:Choking in judo may induce subclinical electroencephalographic perturbations. The extent and duration can be objectified by means of spectral analysis of EEG data, global field power computation, and brain-mapping representation.

ISSN:0195-9131    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Ground reaction forces and EMG activity with ankle bracing during inversion stress.Med. Sci. Sports Exerc.,Vol. 30, No. 9, pp. 1363-1370, 1998.Purpose:The purpose of this investigation was to evaluate the effects of external ankle support on ground reaction forces and myoelectrical activity of selected lower extremity muscles during dynamic inversion stress.Methods:Twenty-four healthy males performed five trials of a lateral dynamic movement at a rate between 80-90% of their maximal speed under three ankle brace conditions (no brace-control, Aircast Sport-Stirrup, Active Ankle). Ground reaction forces along the mediolateral axis and EMG activity of the peroneus longus, tibialis anterior, and medial gastrocnemius were simultaneously recorded during force plate contact.Results:Ankle bracing did not affect peak impact force (P> 0.05), maximum loading force (P> 0.05), or peak propulsion force (P> 0.05) in the lateral direction compared with the control condition. Ankle bracing reduced the EMG activity of the peroneus longus during peak impact force compared with the control condition (P< 0.05), although no differences were noted between the two braces. Furthermore, peroneous longus activity during maximum loading force and peak propulsion remained unaffected (P< 0.05). Ankle bracing did not affect the EMG activity of the tibialis anterior and medial gastrocnemius at the point of peak impact force, maximum loading force (P> 0.05), and peak propulsion force (P> 0.05).Conclusions:These data suggest that ankle bracing may not affect the forces experienced at the foot and ankle, but helps reduce the strain placed on the peroneus longus during peak impact force. Furthermore, ankle bracing does not alter the function of the tibialis anterior and medial gastrocnemius during dynamic inversion stress.

ISSN:0195-9131    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Isometric and dynamic exercise studied with echo planar magnetic resonance imaging (MRI).Med. Sci. Sports Exerc.,Vol. 30, No. 9, pp. 1374-1380, 1998.Purpose:The effect of different types of exercise upon echo planar (EP) magnetic resonance (MR) images was examined during and after both dynamic and isometric dorsi-flexion exercises at matched workloads and durations.Methods:Healthy untrained subjects performed either dynamic exercise through a full range of motion and against a constant resistance or isometric exercise at the center of the range of motion and against a constant resistance at 25 or 70% their measured maximum voluntary contraction(MVC). EP MR images were acquired at 1.5 T every 4 s before (4 images), during (27 images), and after (29-65 images) exercise. A spin echo EP sequence was employed with TE = 30 ms, TR = 4000 ms, FOV = 20 × 40 cm, 64 × 128 matrix. The changes in proton transverse relaxation rate (ΔR2, [s−1]) relative to values obtained before exercise were calculated from individual images at different times during and after exercise.Results:At both 70 and 25% of MVC, the maximum ΔR2after dynamic exercise (−8.38± 0.32s−1(70%), −6.47 ± 1.23s−1(25%)) was significantly greater (P≤ 0.05) than after isometric exercise(−5.91 ± 0.67s−1(70%), −3.80 ± 0.87s−1(25%)). Throughout the period that recovery was monitored, the recovery patterns of ΔR2following isometric and dynamic exercise at both workloads remained parallel.Conclusions:We conclude that exercise-induced changes in MR images are influenced not only by workload and exercise duration but also by the type of exercise, and we postulate that these differences result from the different physiological responses elicited by the different types of exercise.

ISSN:0195-9131    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Maximal oxygen uptake: "classical" versus "contemporary" viewpoints: a rebuttal.Med. Sci. Sports Exerc.,Vol. 30, No. 9, pp. 1381-1398, 1998. Bassett and Howley contend that the 1996 J. B. Wolffe lecture is erroneous because: 1) A. V. Hill did establish the existence of the "plateau phenomenon," 2) the maximum oxygen consumption (V˙O2max) is limited by the development of anaerobiosis in the active muscle, and 3) endurance performance is also determined by skeletal muscle anaerobiosis because the V˙O2maxis the best predictor of athletic ability. As a result, 4) cardiovascular and not skeletal muscle factors determine endurance performance. They further contend that Hill's "scientific hunches were correct," requiring "only relatively minor refinements" in the past 70 yr. But the evidence presented in this rebuttal shows that Hill neither sought nor believed in either the "plateau phenomenon" or the concept of the individual maximum oxygen consumption. These twin concepts were created by Taylor et al.(97)in 1955 and erroneously attributed to Hill. Rather Hill believed that there was a universal human V˙O2maxof 4 L·min−1. His error resulted from his incorrect belief that the real V˙O2, unmeasurable because it includes a large "anaerobic component," rose exponentially at running speeds greater than 13.2 km·h−1. But Hill and his colleagues were indeed the first to realize the danger that a plateau in cardiac output (CO) and hence in V˙O2would pose for the heart itself. For unlike skeletal muscle, the pumping capacity of the heart is both dependent on, but also the determinant of, its own blood supply. Thus, if the CO reaches a peak causing the "plateau phenomenon," the immediate cause of that peak will have been a plateau in myocardial oxygen delivery, causing a developing myocardial ischemia. The ischemia must worsen as exercise continues beyond the supposed V˙O2"plateau." To accommodate this dilemma, Hill and his colleagues proposed a governor "either in the heart muscle or in the nervous system" necessary to prevent myocardial ischemia developing during maximal exercise. This governor would cause maximal exercise to terminate before the development of a plateau in either coronary flow, CO, or V˙O2, or the onset of skeletal muscle anaerobiosis. Accordingly, a new physiological model is proposed in which skeletal muscle recruitment is regulated by a central "governor" specifically to prevent the development of a progressive myocardial ischemia that would preceed the development of skeletal muscle anaerobiosis during maximum exercise. As a result cardiovascular function "limits" maximum exercise capacity, probably as a result of a limiting myocardial oxygen delivery. The model is compatible with all the published findings of cardiovascular function during exercise in hypobaric hypoxia, in which there is a greater likelihood that myocardial hypoxia will develop.

ISSN:0195-9131    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Biorhythmic influences on functional capacity of human muscle and physiological responses.Med. Sci. Sports Exerc.,Vol. 30, No. 9, pp. 1399-1407, 1998. Previously, this laboratory has demonstrated that exhaustive aerobic exercise performance is not subject to significant chronobiological variation between 0800 and 2000 h, but certain physiological responses to maximal aerobic effort do fluctuate significantly within that time frame.Purpose:The purpose of the present investigation was to determine whether muscle performance, and selected physiological responses to resistance exercise, was significantly influenced by time of day effects.Methods:Ten healthy, but untrained, men (21.1 ± 0.6 yr, mean ± SE) volunteered to participate in the study. In a balanced and randomized study design, each subject performed resistance exercise protocols on an isokinetic dynamometer with maximal effort at 0800 h, 1200 h, 1600 h, and 2000 h. Selected physiological and hormonal data were recorded before and immediately following the exercise stimulus.Results:The data demonstrated significant chronobiological oscillation in peak torque, average power, maximal work in a single repetition, and total work per set. Interestingly, this oscillation was manifested only at the fastest velocities of limb movement utilized. Pre- and postexercise rectal temperature exhibited significant time of day fluctuation, as did postexercise blood pressure. Plasma levels of testosterone and cortisol also displayed significant biorhythmicity under both pre- and postexercise conditions. However, exercise-induced responses (pre- to postexercise differences) of those steroid hormones did not exhibit significant biorythmic variation. Although plasma concentrations of both testosterone and cortisol were highest at 0800 h, testosterone to cortisol ratios were greatest at 2000 h.Conclusions:In summary, these data suggest that maximal muscle performance does vary within the segment of the day when exercise typically occurs (0800-2000 h) but that this variation is specific to speed of movement.

ISSN:0195-9131    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Exercise, smoking cessation, and short-term changes in serum lipids in women: a preliminary investigation.Med. Sci. Sports Exerc.,Vol. 30, No. 9, pp. 1414-1418, 1998.Purpose:This study investigated the combined effects of exercise and smoking cessation on serum lipids.Methods:Eighteen female smokers quit smoking using standard behavioral methods combined with exercise(N= 9) or with a nonexercise contact time control (N= 9). The smoking cessation program for both groups consisted of 12 weekly 1-h behavioral modification sessions held over 12 wk. Exercise training consisted of three supervised 45-min sessions per week for 12 wk. Contact control consisted of three health education lectures/discussions per week for 12 wk. Fitness (estimated V˙O2peak), dietary variables, and fasting serum lipids and lipoproteins were assessed before and at the end of treatment. V˙O2peak increased in the exercise subjects compared with the controls.Results:Total caloric intake as well as total fat and carbohydrate increased significantly after smoking cessation in the controls, but there were no dietary changes in the exercise group. high density lipoprotein (HDL)-C2increased (7.6 mg·dL−1,P< 0.01) in the exercise group, whereas the increases in HDL and its subfractions did not attain statistical significance in the contact control group. Total cholesterol, low density lipoprotein (LDL)-C, and triglycerides did not change in either group.Conclusions:We conclude that exercise training magnifies the increase in HDL-C that usually occurs with smoking cessation.

ISSN:0195-9131    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Cardiovascular and metabolic costs of forward, backward, and lateral motion.Med. Sci. Sports Exerc.,Vol. 30, No. 9, pp. 1419-1423, 1998.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 V˙O2max54.13 ± 7.42 mL·kg−1·min−1. Subjects were evaluated at 80.45 and 134.08 m·min−1. A repeated measures ANOVA was used for statistical analysis (P< 0.05).Results:At 80.45 m·min−1, the following respective V˙O2mL·kg−1·min−1and heart rate (HR) beats·min−1responses were: FM = 12.42 ± 2.29, 113 ± 10; BM = 15.95 ± 2.45, 132 ± 16; and LM = 22.10± 4.76, 140 ± 15. Both V˙O2and HR were significantly different between conditions: LM > BM > FM. At 134.08 m·min−1, the following respective V˙O2and 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·min−1neither HR or V˙O2were 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.

ISSN:0195-9131    

出版商:OVID    

年代:1998

数据来源: OVID

摘要:

Lactate distribution in the blood during steady-state exercise.Med. Sci. Sports Exerc.,Vol. 30, No. 9, pp. 1424-1429, 1998.Purpose:The purpose of this investigation was to examine the plasma to red blood cell (RBC) lactate concentration ([La]) gradient and RBC:plasma [La] ratio during 30 min of steady-state cycle ergometer exercise at work rates below lactate threshold(<LT = ~≈40% of peak cycle ergometer O2uptake {V˙O2peak}) and above LT (≈70% of V˙O2peak).Methods:Eight subjects (cycling V˙O2peak= 41.6 ± 1.6 mL·kg−1·min−1; LT = 57.9 ± 1.2% V˙O2peak) performed 30 min of cycle exercise at intensities < and > LT. Blood samples were taken from a heated forearm vein, immediately cooled to 4°C in a dry-ice ethanol slurry, and centrifuged at 4°C to separate plasma and RBCs.Results:During >LT, plasma[La] rose to 8.8 ± 1.1 mM after 10 min and remained above 6 mM. RBC [La] (4.9 ± 0.7 mM) was significantly lower than plasma [La] at 10 min and remained lower throughout exercise. As a result, there was a sizable[La] gradient (≈3.5 mM) from plasma to RBC during most of >LT. In<LT, plasma [La] increased only slightly from rest (1.6 ± 0.2 mM) after 6 min (2.4 ± 0.3 mM) and then declined to ≈2 mM for the remainder of the trial. The plasma to RBC [La] gradient averaged ≈0.8 mM throughout<LT. Despite drastically different plasma to RBC [La] gradients in <LT and >LT, the ratio of RBC [La]:plasma [La] was the same for both (0.58 ± 0.02) and not significantly different from rest.Conclusions:These results refuted our hypothesis that the RBC:plasma [La] ratio would decrease at the onset of >LT exercise because of muscle lactate release exceeding the ability of RBCs to take up the lactate. Instead, there appears to be an equilibrium between plasma [La] and RBC [La] in arterialized venous blood from a resting muscle group as evidenced by the constant RBC [La]:plasma [La] ratio.

ISSN:0195-9131    

出版商:OVID    

年代:1998

数据来源: OVID