Strength training: Isometric training at a range of joint angles versus dynamic training

Strength training with isometric contractions produces large but highly angle-specific adaptations. To contrast the contractile mode of isometric versus dynamic training, but diminish the strong angle specificity effect, we compared the strength gains produced by isometric training at four joint angles with conventional dynamic training. Thirty-three recreationally active healthy males aged 18?–?30 years completed 9 weeks of strength training of the quadriceps muscle group three times per week. An intra-individual design was adopted: one leg performed purely isometric training at each of four joint angles (isometrically trained leg); the other leg performed conventional dynamic training, lifting and lowering (dynamically trained leg). Both legs trained at similar relative loads for the same duration. The quadriceps strength of each leg was measured isometrically (at four angles) and isokinetically (at three velocities) pre and post training. After 9 weeks of training, the increase in isokinetic strength was similar in both legs (pooled data from three velocities: dynamically trained leg, 10.7%; isometrically trained leg, 10.5%). Isometric strength increases were significantly greater for the isometrically trained leg (pooled data from four angles: dynamically trained leg, 13.1%; isometrically trained leg, 18.0%). This may have been due to the greater absolute torque involved with isometric training or a residual angle specificity effect despite the isometric training being divided over four angles.     

Effect of Optimized and Standard Cycle Ergometry on VO2max in Trained Cyclists and Runners

Abstract

This study contrasted prepractice modeling with either the perceptual component (perceptual modeling) or the motor component (movement pattern) of a coincident-timing task to determine whether experiencing the modalities singly or in combination enhanced timing performance on initiation of active practice. The motor component was a 60-cm right-to-left arm movement coincident with the illumination of lights on a Bassin timer runway to displace a barrier as the final runway light was illuminated. Four groups were compared (n = 12 per group). A perceptual modeling group passively viewed stimulus runway lights prior to attempting the task. A motoric modeling group viewed a videotape prior to practice of a model performing the motor component of the skill with zero timing error. A perceptual modeling plus motoric modeling group experienced both modeling modalities prior to performance. Finally, a no modeling group simply initiated practice on the task without modeling. Results indicated that the groups experiencing perceptual modeling initiated practice with significantly less average timing error and variability. Thus, perceptual modeling appeared to be at least as important as motoric modeling as a source of prepractice information to make available to a learner to optimize coincident-timing skill acquisition.     

High-intensity interval running is perceived to be more enjoyable than moderate-intensity continuous exercise: Implications for exercise adherence

Abstract

The aim of this study was to objectively quantify ratings of perceived enjoyment using the Physical Activity Enjoyment Scale following high-intensity interval running versus moderate-intensity continuous running. Eight recreationally active men performed two running protocols consisting of high-intensity interval running (6×3 min at 90% [Vdot]O_2max interspersed with 6×3 min active recovery at 50% [Vdot]O_2max with a 7-min warm-up and cool down at 70% [Vdot]O_2max) or 50 min moderate-intensity continuous running at 70% [Vdot]O_2max. Ratings of perceived enjoyment after exercise were higher (P < 0.05) following interval running compared with continuous running (88 ± 6 vs. 61 ± 12) despite higher (P < 0.05) ratings of perceived exertion (14 ± 1 vs. 13 ± 1). There was no difference (P < 0.05) in average heart rate (88 ± 3 vs. 87 ± 3% maximum heart rate), average [Vdot]O₂ (71 ± 6 vs. 73 ± 4%[Vdot]O_2max), total [Vdot]O₂ (162 ± 16 vs. 166 ± 27 L) or energy expenditure (811 ± 83 vs. 832 ± 136 kcal) between protocols. The greater enjoyment associated with high-intensity interval running may be relevant for improving exercise adherence, since running is a low-cost exercise intervention requiring no exercise equipment and similar relative exercise intensities have previously induced health benefits in patient populations.     

Markers of isometric training intensity and reductions in resting blood pressure

Abstract

In this study, we examined the correlations between selected markers of isometric training intensity and subsequent reductions in resting blood pressure. Thirteen participants performed a discontinuous incremental isometric exercise test to volitional exhaustion at which point mean torque for the final 2-min stage (2min-torque_peak) and peak heart rate peak (HR_peak) were identified. Also, during 4 weeks of training (3 sessions per week, comprising 4 × 2 min bilateral leg isometric exercise at 95% HR_peak), heart rate (HR_train), torque (Torque_train), and changes in EMG amplitude (ΔEMG_amp) and frequency (ΔEMG_freq) were determined. The markers of training intensity were: Torque_train relative to the 2min-torque_peak (%2min-torque_peak), EMG relative to EMG_peak (%EMG_peak), HR_train ΔEMG_amp, ΔEMG_freq, and %MVC. Mean systolic (?4.9 mmHg) and arterial blood pressure (?2.7mmHg) reductions correlated with %2min-torque_peak (r = ?0.65, P = 0.02 and r = ?0.59, P = 0.03), ΔEMG_amp (r = 0.66, P = 0.01 and r = 0.59, P = 0.03), ΔEMG_freq (r = ?0.67, P = 0.01 and r = ?0.64, P = 0.02), and %EMG_peak (systolic blood pressure only; r = ?0.63, P = 0.02). These markers best reflect the association between isometric training intensity and reduction in resting blood pressure observed after bilateral leg isometric exercise training.     

Effect of 6 weeks of endurance training on the lactate minimum speed

The aim of this study was to assess the sensitivity of the lactate minimum speed test to changes in endurance fitness resulting from a 6 week training intervention. Sixteen participants (mean +/- s :age 23 +/- 4 years;body mass 69.7 +/- 9.1 kg) completed 6 weeks of endurance training. Another eight participants (age 23 +/- 4 years; body mass 72.7 +/-12.5 kg) acted as non-training controls. Before and after the training intervention, all participants completed: (1) a standard multi-stage treadmill test for the assessment of VO 2max , running speed at the lactate threshold and running speed at a reference blood lactate concentration of 3 mmol.l -1 ; and (2) the lactate minimum speed test, which involved two supramaximal exercise bouts and an 8 min walking recovery period to increase blood lactate concentration before the completion of an incremental treadmill test. Additionally, a subgroup of eight participants from the training intervention completed a series of constant-speed runs for determination of running speed at the maximal lactate steady state. The test protocols were identical before and after the 6 week intervention. The control group showed no significant changes in VO 2max , running speed at the lactate threshold, running speed at a blood lactate concentration of 3 mmol.l -1 or the lactate minimum speed.In the training group, there was a significant increase in VO 2max (from 47.9 +/- 8.4 to 52.2 +/- 2.7 ml.kg -1 .min -1 ), running speed at the maximal lactate steady state (from 13.3 +/- 1.7 to 13.9 +/- 1.6 km.h -1 ), running speed at the lactate threshold (from 11.2 +/- 1.8 to 11.9 +/- 1.8 km.h -1 ) and running speed at a blood lactate concentration of 3 mmol.l -1 (from 12.5 +/- 2.2 to 13.2 +/- 2.1 km.h -1 ) (all P ? 0.05). Despite these clear improvements in aerobic fitness, there was no significant difference in lactate minimum speed after the training intervention (from 11.0 +/- 0.7 to 10.9 +/- 1.7 km.h -1 ). The results demonstrate that the lactate minimum speed,when assessed using the same exercise protocol before and after 6 weeks of aerobic exercise training, is not sensitive to changes in endurance capacity.     

Book review

Suzanne Grant Lewis and Joel Samoff, eds., Microcomputers in African Development: Critical Perspectives (Boulder, CO: Westview Press, 1992), 258 pp., $42.50 (ISBN 0–8133–7934–2).     

Effects of Two Instructional Approaches on Skill Development,Knowledge, and Game Performance

Two instructional approaches that have been of interest in promoting sport have been the Sport Education Model (SEM) and the Traditional Style (TS) of teaching physical education. The purpose of this study was to investigate how SEM and TS would affect skill development, knowledge, and game performance for volleyball at the secondary level. A 2 × 3 (group × time) research design was utilized on 47 secondary students testing volleyball skills, knowledge, and game performance. Participants were placed in either the SEM or the TS via stratified randomization, and then were tested pre, mid, and post intervention through the 20-lesson volleyball unit. The 2 × 3 repeated measures Analysis of Variances (ANOVAs) with Bonferroni correction revealed no significant difference between models for skills and knowledge, but there was for game performance for group [F(1, 45) = 10.27, p < .008, η² = .19], time [F(2, 90) = 8.62, p < .008, η² = .16], and group × time interaction [F(2, 90) = 8.43, p < .008, η² = .16]. If the goal of the physical education program is to promote quality game play, the SEM may be more effective than the TS.     

The Role of Gender-related Information and Self-Endorsement of Traits in Preadolescents' Inferences and Judgments

The major purpose of this study was to examine the effects of a target child's gender typicality on different aspects of preadolescents' inferences and judgments. The secondary purpose of the study was to investigate the relation between children's self-endorsement of traits and their inferences and judgments. Fifth and sixth graders were shown a video film, portraying a child playing either a gender-appropriate game with members of the same sex or a gender-inappropriate game with members of the other sex. In addition, subjects completed an adapted version of the BSRI and were categorized into sex-typed, androgynous, and undifferentiated subjects. Subjects made a number of different types of judgments and inferences about the target, including inferences about traits, popularity, choice of gift and name, and willingness to engage in activities with the target. All types of inferences and judgments were affected by the variations in the targets' gender-related behaviors, whereas self-endorsement of traits was not related to the inferences and judgments. The results suggest that the gender typicality of the target behavior is salient to preadolescents, regardless of their sex-role orientation.