摘要:

COLLINS, M. A., K. J. CURETON, D. W. HILL, and C. A. RAY. Relation of plasma volume change to intensity of weight lifting.Med. Sci. Sports Exerc, Vol. 21, No. 2, pp. 178–185, 1989. To determine the relation of plasma volume change to intensity of weight lifting, blood samples were obtained from 15 males [mean (±SD) age = 22.3 ± 3.2 yr; height = 176.3 ± 6.9 cm; weight = 73.0 · 11.7 kg] before and over a 60-min period following weight lifting at four different intensities [40, 50, 60, and 70% of one-repetition maximum (1-RM)]. Weight lifting consisted of completing three circuits of four exercises (bench press, bent-over row, arm curl, and parallel squat), with 10 repetitions of each exercise performed over a 30-s period followed by 30 s of rest. Mean (±SE) oxygen uptakes (&OV0312;O2) during weight lifting at the four intensities were 1.31 ± 0.04, 1.50 ± 0.07, 1.72 ± 0.07, and 1.86±0.08 1·min-1, or 33–47% of treadmill-determined &OV0312;O2maxrespectively. Mean (±SE) blood lactates were 6.5 ± 0.5, 8.7 ± 0.5, 9.4 ± 0.6, and 12.0 ± 0.6 mmol·l-1, respectively. Mean (±SE) heart rates (HR) were 124 ± 4, 134 ± 4, 148 ± 5, and 161 ± 4 bpm, or 63–82% of treadmill-determined HRmax, respectively. Plasma volume decreased linearly in relation to intensity of weight lifting with mean responses of −7.7 ± 0.8, −10.7 ± 0.8, −12.1 ± 0.9, and −13.9 ± 0.8% at 40, 50, 60, and 70% of 1-RM, respectively. It was concluded that plasma volume decreases linearly in relation to intensity (%1-RM) of weight lifting and that the relation is similar to that reported for dynamic, low-resistance exercise such as cycling and running.

ISSN:0195-9131    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

HARMAN, E. A., R. M. ROSENSTEIN, P. N. FRYKMAN, and G. A. NIGRO. Effects of a belt on intra-abdominal pressure during weight lifting.Med. Sci. Sports Exerc, Vol. 21, No. 2, pp. 186–190, 1989. Intra-abdominal pressure (IAP) has been widely hypothesized to reduce potentially injurious compressive forces on spinal discs during lifting. To investigate the effects of a standard lifting belt on IAP and lifting mechanics, IAP and vertical ground reaction force (GRF) were monitored by computer using a catheter transducer and force platform while nine subjects aged 28.2 ± 6.6 yr dead-lifted a barbell both with and without a lifting belt at 90% of maximum. Both IAP and GRF rose sharply from the time force was first exerted on the bar until shortly after it left the floor, after which GRF usually plateaued while IAP either plateaued or declined. IAP rose significantly (P<0.05) earlier with than without the belt. When the belt was worn, IAP rose significantly earlier than did GRF. Both with and without the belt, IAP ended its initial surge significantly earlier than did GRF. Variables significantly greater with than without a belt included peak IAP, area under the IAP vs time curve from start of initial IAP surge to lift-off, peak rate of IAP increase after the end of its initial surge, and average IAP from lift-off to life completion. In contrast, average rate of IAP increase during its initial surge was significantly lower with the belt. Correlations are presented which provide additional information about relationships among the variables. Results suggest that the use of a lifting belt increases IAP, which may reduce disc compressive force and improve lifting safety.

ISSN:0195-9131    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

MCLELLAN, T. M. and G. C. CASS. Metabolic and cardiorespiratory responses relative to the anaerobic threshold.Med. Sci. Sports Exerc, Vol. 21, No. 2, pp. 191–198, 1989. The present study has compared the metabolic and cardiorespiratory responses for two groups of male subjects during 20 min of exercise at the anaerobic threshold (AT), at AT+1/3, and at AT+2/3 of the difference (Δ) between AT and &OV0312;O2max. A log-log transformation of the lactate (LA)-power output relationship was used to define AT and divide subjects into a high (N= 7, AT = 51.9 ± 1.5% &OV0312;O2max) and low (N= 5; AT = 41.9 ± 1.8% &OV0312;O2max) AT group. No differences were observed between groups during exercise at AT for &OV0312;E·&OV0312;O2-1, &OV0312;E·&OV0312;CO2-1pH, pCO2, blood LA, and plasma strong ions Na+, K+, and Cl-. Although blood LA values were significantly elevated for the low AT subjects (2.3 ± 0.6 mmol·l-1) compared with the high AT group (1.0 ± 0.1 mmol·l-1) during exercise at AT+1/3Δ, no other differences between groups were noted. In contrast, marked differences were observed between groups during exercise at AT+2/3Δ. The high AT group showed no change in &OV0312;E(79.1 ± 4.8 1·min-1), pH (7.367 ± 0.01), pCO2(37.3 ± 1.2 mm Hg), and blood LA (2.9 ± 0.3 mmol·l-1) during the final 10 min of the 20 min exercise test. The low AT group, however, showed a progressive increase in &OV0312;E(from 88.7 ± 4.2 to 108.0 ± 8.0 1·min-1) and blood LA (from 8.6 ± 1.0 to 11.4 ± 2.7 mmol·l-1) and a progressive decrease in blood pH (from 7.294 ± 0.014 to 7.251 ± 0.030) and pCO2(from 35.2 ± 1.2 to 29.2 ± 1.3 mm Hg) from minute 10 to minute 20 of exercise. These data suggest that AT and &OV0312;O2maxdo not provide common reference points for calculating exercise intensity and/or that a metabolic rate exists above AT and below &OV0312;O2maxthat defines an individual's maximal steady state for the cardiorespiratory and metabolic response to exercise.

ISSN:0195-9131    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

WEYRICH, A. S., S. P. MESSIER, B. S. RUHMANN, and M. J. BERRY. Effects of bat composition, grip firmness, and impact location on postimpact ball velocity.Med. Sci. Sports Exerc, Vol. 21, No. 2, pp. 199–205, 1989. The purpose of this investigation was to examine the effects of bat composition (aluminum and wooden), impact location [center of percussion (COP), center of gravity (COG), and end of the bat (E)], and grip firmness [tight (T) and no tension (NT)] on postimpact ball velocity. With the bats placed alternately in NT and T conditions, baseballs were delivered at a speed of 27.1 m · s-1from a pitching machine positioned 1.5 m from the bat. Highspeed photography (400 fps) was performed using a Locam camera positioned 7.54 m from and perpendicular to the principal plane of ball movement. A three-way ANCOVA revealed significant (P< 0.01) differences in postimpact ball velocity between the three impact locations, with the COP yielding the greatest values, followed by the COG and E. Moreover, there was a significant (P<0.01) grip vs bat interaction. A simple-effects procedure revealed the following results: 1) the T grip produced greater (P<0.01) velocities than the NT grip across the aluminum (Al) bat; 2) there was no difference (P>0.01) between the T and NT grips across the wooden (W) bat; 3) the W bat produced greater (P<0.01) velocities than the Al bat across the NT grip; and 4) there was no difference (P>0.01) between the Al and W bats across the T grip. It was concluded that: ball-bat contact at the COP produces the greatest postimpact ball velocity of the three impact locations studied; a T grip enhances postimpact ball velocity relative to a NT grip, especially when using an Al bat; and postimpact ball velocity produced by W and Al bats favors W bats.

ISSN:0195-9131    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

DAPENA, J. and C. MCDONALD. A three-dimensional analysis of angular momentum in the hammer throw.Med. Sci. Sports Exerc, Vol. 21, No. 2, pp. 206–220, 1989. Eight hammer throwers were studied using three-dimensional cinematography. The local term of angular momentum of each thrower (HTL) followed a wide conical path, while the remote term (HTR) and the hammer angular momentum (HH) followed much narrower conical paths.HT, the sum of (HTLandHTR, followed a conical path similar to that ofHTL, although with smaller amplitude.HH, was half of a cycle out of phase with HT. It was also larger but followed a narrower conical path. As a result, the conical paths ofHHandHTcounteracted each other, andHs, the total angular momentum vector of the thrower-hammer system, had little conical motion. The paths of the angular momentum vectors, the trunk tilt, and the height of the hammer plane relative to the system center of mass were interrelated. Some throwers kept the hammer plane high and the trunk tilting back in all the turns; other throwers kept the hammer plane low and the trunk tilting forward in the early turns, but the hammer plane rose in their late turns and the trunk tilted back. Two theories were proposed to explain why the athletes who had forward trunk tilt in the early turns tilted backward in the final part of the throw.

ISSN:0195-9131    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

LEWTHWAITE, R., and T. K. SCANLAN. Predictors of competitive trait anxiety in male youth sport participants.Med. Sci. Sports Exerc, Vol. 21, No. 2, pp. 221–229, 1989. This field study examined intra-personal and significant adult factors related to the levels of dispositional or competitive trait anxiety experienced by 9− to 14-yr-old male participants of a competitive wrestling program. Competitive trait anxiety (CTA) is a personality disposition which reflects the tendency to experience stress in situations involving competitive sport (20). Multiple regression analyses of questionnaire data revealed that boys with more frequent somatic competitive trait anxiety symptoms 1) had lower self-esteem, 2) reported greater upset if they performed poorly, and 3) expressed a greater preference for avoiding a tournament match. Investigated cognitive anxiety symptoms involved characteristic precompetitive worries about failure and worries about adult expectations and evaluation. Youngsters with more frequent worries about failure placed greater importance on wrestling well and felt greater upset when they performed poorly, in comparison with boys who worried less frequently about failure. More frequent adult-related worries were predicted by greater personal upset for poor performance and perceptions of 1) greater parental and coach shame and upset, 2) more negative adult evaluations, and 3) greater parental pressure to wrestle.

ISSN:0195-9131    

出版商:OVID    

年代:1989

数据来源: OVID

摘要:

PARKER, S.B., B. F. HURLEY, D. P. HANLON, AND P. VACCARO. Failure of target heart rate to accurately monitor intensity during aerobic dance.Med. Sci. Sports Exerc, Vol. 21, No. 2, pp. 230–234, 1989. Fourteen untrained females (age 19 ± 1, range 18–21) were studied to examine the heart rate-&OV0312;O2relationship during a single aerobic dance training session. These findings were used to help explain the changes in &OV0312;O2maxresulting from an aerobic dance training program. &OV0312;O2manand body composition were determined before and after an 8 wk training period. In addition, the heart rate-&OV0312;O2responses to an aerobic dance training session were monitored and compared to the heart rate responses of treadmill jogging performed at the same &OV0312;O2. The aerobic dance session elicited a significantly lower oxygen pulse than did treadmill exercise (7.2 ± 0.3 vs 8.1 ± 0.8 ml·beat-1;P< 0.01). There were no significant changes in percent body fat, whereas &OV0312;O2maxincreased by 11 % (34.4 ± 0.9 vs 38.1 ± 0.8 ml·kg-1·min-1;P< 0.05). No significant changes in any of the parameters tested were observed in 10 untrained controls. These findings indicate that the heart rate elicited from aerobic dance represents a lower relative exercise intensity (&OV0312;O2) than that of running. Therefore, the assumption that aerobic dance training produces the same cardiovascular adaptations as running training when performed at the same target rate may be unwarranted.

ISSN:0195-9131    

出版商:OVID    

年代:1989

数据来源: OVID

ISSN:0195-9131    

出版商:OVID    

年代:1989

数据来源: OVID

ISSN:0195-9131    

出版商:OVID    

年代:1989

数据来源: OVID