Strength training,but not endurance training,reduces motor unit discharge rate variability

This study evaluates and compares the effects of strength and endurance training on motor unit discharge rate variability and force steadiness of knee extensor muscles. Thirty sedentary healthy men (age, 26.0 ± 3.8 yrs) were randomly assigned to strength training, endurance training or a control group. Conventional endurance and strength training was performed 3 days per week, over a period of 6 weeks. Maximum voluntary contraction (MVC), time to task failure (at 30% MVC), coefficient of variation (CoV) of force and of the discharges rates of motor units from the vastus medialis obliquus and vastus lateralis were determined as subjects performed 20% and 30% MVC knee extension contractions before and after training. CoV of motor unit discharges rates was significantly reduced for both muscles following strength training (P < 0.001), but did not change in the endurance (P = 0.875) or control group (P = 0.995). CoV of force was reduced after the strength training intervention only (P < 0.01). Strength training, but not endurance training, reduces motor unit discharge rate variability and enhances force steadiness of the knee extensors. These results provide new insights into the neuromuscular adaptations that occur with different training methods.     

Strength training and aerobic exercise: comparison and contrast

Most exercise programs for conditioning and rehabilitation are oriented to strength development, aerobic (cardiovascular) fitness, or a combination of the 2. Because the 2 types of exercise are located at the opposite extremes of a muscular power continuum, the design of a program must be highly specific with regard to the exercise to be undertaken, as well as the intensity, duration, and frequency, in order to attain optimal results. Strength exercise programs involve weight training or the use of high-resistance machines with exercise that is limited to a few repetitions (generally less than 20) before exhaustion. Aerobic exercise involves exercise performed for extended periods (e.g., 10-40 minutes) with large muscle activity involving hundreds of consecutive repetitions that challenge the delivery of oxygen to the active muscles. The chronic physiological adaptations and the variables in program design are highly specific to the type of exercise performed.     

Strength/power augmentation subsequent to short-term training abstinence

Strength augmentation has been demonstrated in resistance-trained men subsequent to 4 days of training abstinence. However, this phenomenon was exhibited in an unusual circumstance in which the exercise test (seated heel raise) primarily involved an isolated skeletal muscle (soleus) that is normally comprised almost exclusively of 1 fiber type. It is unclear if similar results would be found for aggregate muscle actions. Therefore, a comparable study was designed with this in mind. Subjects were apparently healthy, young, strength-trained men (n = 25). All performed various tests of bench press strength at the beginning of their last standardized dynamic constant external resistance (DCER) training session. Subjects were subsequently randomly assigned to 1 of 4 groups and repeated the identical tests at intervals of either 2, 3, 4, or 5 days with no intervening training. Strength tests consisted of 1 repetition maximum (1RM) concentric-only isokinetic bench presses performed at 1.49 and 0.37 m.s(-1) as well as a 1RM DCER bench press. Measures of peak force and power were obtained from the isokinetic tests and maximum load from the DCER test. Results were expressed in both absolute and relative (to body weight) terms. Subsequent to the 4 abstinence intervals, groups performed similarly (p > 0.05) for all dependent variables. Concurrently, however, a small effect size (ES) was found for the group having a 4-day respite for both absolute and relative expressions of peak force and power at the slowest isokinetic bench press velocity. A small ES was also identified for the group having 2 days of rest for relative peak force at the slowest isokinetic test velocity and for relative DCER strength. Therefore, modest and transient strength augmentation appears likely in aggregate muscle actions following 2-4 days of training abstinence in resistance-trained men, but only at relatively slow velocities.     

Strength training for 1h in humans: effect on the motor performance of normal upper extremities

It has been found that one session of intense muscle strength training decreases muscle strength temporarily and causes neuromuscular fatigue in the trained muscles, but little attention has been given to the effects of neuromuscular fatigue on the other components of motor performance. The purpose of this study was to examine in normal healthy volunteers the effects of a 1-h strength training session on the motor performance of the upper extremity, including reaction time, speed of movement, tapping speed and coordination. Group of 30 healthy female volunteers, aged 29-47 years, were randomly divided into sub-groups, (A and B, n = 15 per group). Both groups first completed a set of motor performance tests on 3 consecutive days. On the 4th day, group A carried out a 1-h muscle strength training session of the upper extremities. Isometric muscle strengths and electromyogram (EMG) data were recorded before the training session. Immediately after the training session the same recordings were repeated, and additional motor performance tests were also performed. Group B carried out only the motor performance tests. The groups exchanged programmes the following week. The 1-h strength training session decreased the isometric muscle strength of wrist flexion by 18% (P < 0.001) and extension by 18% (P < 0.001) in group A, while in group B flexion strength decreased by 19% (P < 0.001) and extension strength by 17% (P < 0.001). All the measured EMG activations also decreased in both groups. There were no statistically significant differences in the results of the motor performance tests between the mean values of the three baseline measurements and the values recorded after the training session. The result was surprising, but straightforward; neuromuscular fatigue induced by a 1-h strength training session of the upper extremities had no effect on the motor performance functions of the hand, as indicated by reaction times, speed of movement, tapping speed and coordination, in these normal healthy female volunteers.     

The National Strength and Conditioning Association is the preferred certification for personal training employment in southeastern Massachusetts

Offering a college program in exercise science presents challenges when attempting to mainstream credentialed students into the fitness industry, specifically as personal trainers. Unfortunately, today's clubs, regardless of their education or degree, are more interested in hiring personal trainers with specific certifications. With the growing number of available certifications, college students are expected to have a college degree and obtain multiple fitness related certifications before being considered for a personal training position. Is a college graduate still required to obtain a personal training certification? In an effort to have the best qualified individuals training clients, i.e., those with degrees, it becomes necessary to know what certification is the most preferred. The purpose of this study was to impact local college curriculums to increase the marketability of degree recipients upon graduation.     

Strength training counteracts motor performance losses during bed rest.

The purpose of the study was to determine the effect of bed rest with or without strength training on torque fluctuations and activation strategy of the muscles. Twelve young men participated in a 20-day bed rest study. Subjects were divided into a non-training group (BRCon) and a strength-training group (BRTr). The training comprised dynamic calf-raise and leg-press exercises. Before and after bed rest, subjects performed maximal contractions and steady submaximal isometric contractions of the ankle extensor muscles and of the knee extensor muscles (2.5-10% of maximal torque). Maximal torque decreased for both the ankle extensors (9%, P < 0.05) and knee extensors (16%, P < 0.05) in BRCon but not in BRTr. For the ankle extensors, the coefficient of variation (CV) for torque increased in both groups (P < 0.05), with a greater amount (P < 0.05) in BRCon (88%) compared with BRTr (41%). For the knee extensors, an increase in the CV for torque was observed only in BRCon (22%). The increase in the CV for torque in BRCon accompanied the greater changes in electromyogram amplitude of medial gastrocnemius (122%) and vastus lateralis (59%) compared with BRTr (P < 0.05). The results indicate that fluctuations in torque during submaximal contractions of the extensor muscles in the leg increase after bed rest and that strength training counteracted the decline in performance. The response varied across muscle groups. Alterations in muscle activation may lead to an increase in fluctuations in motor output after bed rest.     

Strength training and determinants of VO2max in older men

The effects of strength training on maximal aerobic power (VO2max) and some of its determinants were studied in 12 healthy older men (60-72 yr). They underwent 12 wk of strength conditioning of extensors and flexors of each knee with eight repetitions per set, three sets per session, and three sessions per week at 80% of the one repetition maximum (1 RM). Left knee extensors showed a 107% increase in 1 RM, a 10% increase in isokinetic strength at 60 degrees/s, and a 23% increase in total work performed during 25 contractions on an isokinetic dynamometer. Strength measurements of the untrained left elbow extensors showed no change. Leg cycle ergometer VO2max per unit fat-free mass increased by an average 1.9 ml (P = 0.034) whereas arm cycle VO2max was unchanged. Pulmonary function, hemoglobin concentration, erythrocyte volume, plasma volume, and total blood volume did not change. Biopsies of the vastus lateralis showed a 28% increase in mean fiber area, no change in fiber type distribution, a 15% increase in capillaries per fiber, and a 38% increase in citrate synthase activity. The data suggest that the small increase in leg cycle VO2max in older men may be due to adaptations in oxidative capacity and increased mass of the strength-trained muscles.     

Strength cycle training: effects on muscular strength and aerobic conditioning

The strength cycle ergometer has been proposed as a method of simultaneously increasing aerobic conditioning and muscular strength, because of its unique capacity of disengaging the pedal crank, thus allowing for concurrent single-leg cycling. The purpose of this study was to assess the aerobic and muscular strength effects of strength cycle training (SCT), comparing it to similar standard cycle training. A total of 28 recreationally-trained adult subjects (9 men, 19 women) were paired for VO2peak and randomly assigned to either SCT or Monark cycle training (MCT). Subjects trained 3 days per week following a progressive interval protocol for 9 weeks under supervised conditions. Training intervals (5 minutes' duration) consisted of 3 minutes of standard cycling at an intensity of 60-85% of maximum heart rate (HRmax), and 2 minutes of either the disengaged cycling mode (SCT) or standard cycling plus 30 W (MCT). Subjects began training for a total of 25 minutes per session, progressing to 45 minutes per session by study's end. Prior to and following training, subjects were measured for VO2peak; submaximal VO2, heart rate (HR), RPE, power output, and knee and ankle isokinetic strength. Training resulted in significant (p < or = 0.05) increases in VO2peak (14.5%) and submaximal power output (11%), and significant reductions in submaximal VO2, HR, and RPE in both groups. Significant increases in bilateral isokinetic knee extension (4-6%) and left ankle plantar flexion (10.5%) were noted following training in both groups. No group differences were detected in any variable. Although the strength cycle effectively increased aerobic function and resulted in modest selected increases in lower-extremity muscular strength, these changes were not different from those seen using a similar standard cycling protocol.     

Strength training improves the steadiness of slow lengthening contractions performed by old adults.

When old adults participate in a strength-training program with heavy loads, they experience an increase in muscle strength and an improvement in the steadiness of submaximal isometric contractions. The purpose of this study was to determine the effect of light- and heavy-load strength training on the ability of old adults to perform steady submaximal isometric and anisometric contractions. Thirty-two old adults (60-91 yr) participated in a 4-wk training program of a hand muscle. Both the light- and heavy-load groups increased one-repetition maximum and maximal voluntary contraction (MVC) strength and experienced similar improvements in the steadiness of the isometric and shortening and lengthening contractions. The increase in MVC strength was greater for the heavy-load group and could not be explained by changes in muscle activation. Before training, the lengthening contractions were less steady than the shortening contractions with the lightest loads (10% MVC). After training, there was no difference in steadiness between the shortening and lengthening contractions, except with the lightest load. These improvements were associated with a reduced level of muscle activation, especially during the lengthening contractions.     

Strength gains after resistance training: the effect of stressful, negative life events

This study was designed to examine the effect of self-reported, stressful life events on strength gains after 12 weeks of resistance training. Participants were 135 undergraduates enrolled in weight training classes that met for 1.5 hours, two times per week. After a 2-week period to become familiar with weight training, participants completed the college version of the Adolescent Perceived Events Scale (APES), the Social Support Inventory, and one-repetition maximal lifts (1RM) for the bench press and squat. Maximal lifts were repeated after 12 weeks of training. Median splits for stress and social support were used to form groups. Results indicated that the low stress participants experienced a significantly greater increase in bench press and squat than their high stress counterparts. Strength gains were, however, unrelated to social support scores in either the low or high stress group. High life stress may lessen a person's ability to adapt to weight training. It may benefit coaches to monitor their athletes' stress both within and outside the training setting to maximize their recovery and adaptation.     

Strength in diversity: a cross-disciplinary approach to graduate training in chemical biology

Chemical biology graduate programs that are jointly organized by chemistry and life science departments can offer a stimulating 'bicultural' training environment for students from diverse backgrounds. However, communication, flexibility and responsiveness are crucial for effectively structuring such programs.     

Strength in diversity: a cross-disciplinary approach to graduate training in chemical biology

Chemical biology graduate programs that are jointly organized by chemistry and life science departments can offer a stimulating 'bicultural' training environment for students from diverse backgrounds. However, communication, flexibility and responsiveness are crucial for effectively structuring such programs.     

Strength adaptations and hormonal responses to resistance training and detraining in preadolescent males

Nineteen untrained preadolescent males (11-13 years old) were randomly placed into an experimental trained group (STG, n = 9) and a control group (n = 10). Informed consent was obtained from the children and their parents. The STG was submitted to a 2-month resistance-training program (6 exercises, 3 x 10 repetitions maximum [RM], 3 times per week), followed by a 2-month detraining program. The effectiveness of the resistance program was determined by measuring pre- and posttraining and detraining differences in isometric and isotonic (10RM) strength and hormonal responses in testosterone (T), sex hormone binding globulin, and free androgen index (FAI). Their maturation stage was evaluated according to Tanner. Significant posttraining isometric strength gains (17.5%) and mean T and FAI value increases (p < 0.05-0.001) were observed in STG. Detraining resulted in a significant loss (9.5%, p < 0.001) of isometric strength whereas the hormonal parameters of STG remained practically unaltered. The relative (delta%) postdetraining hormonal responses correlated significantly with the respective isometric strength changes. In conclusion, the resistance training induced strength changes independent of the changes in the anabolic and androgenic activity in preadolescent males. Further research is needed to fully clarify the physiological mechanisms underlying the strength training and detraining process.     

Strength training reduces force fluctuations during anisometric contractions of the quadriceps femoris muscles in old adults.

The greater fluctuations in motor output that are often exhibited by old adults can be reduced with strength training. The purpose of the study was to determine the effect of strength and steadiness training by old adults on fluctuations in force and position during voluntary contractions with the quadriceps femoris muscle. Healthy old adults (65-80 yr) completed 16 wk of heavy-load (80% of maximum, n = 11) strength training, heavy-load steadiness training (n = 6), or no training (n = 9). Steadiness training required subjects to match the angular displacement about the knee joint to a constant-velocity template. The Heavy-Load group experienced a 5.5% increase in muscle volume, a 25% increase in maximal voluntary contraction force, and a 26% increase in the one-repetition (1-RM) load. The Heavy-Load Steady group experienced increases of 11.5, 31, and 36%, respectively. The maximal electromyogram signal of quadriceps femoris increased by 51% in the two training groups. The coefficient of variation (CV) for force during submaximal isometric contractions did not change with training for any group. Although both training groups also experienced a reduction in CV for force during anisometric contractions with a 50% 1-RM load, the standard deviation of position did not change with time for any group. The Heavy-Load Steady group also experienced a reduction in CV for force during the training contractions performed with the 80% 1-RM load. Thus strength training reduced the force fluctuations of the quadriceps femoris muscles during anisometric contractions but not during isometric contractions.     

Strength training during pregnancy influences hippocampal plasticity but not body development in neonatal rats

Objective:To describe the effects of strength exercise practice during pregnancy on the offspring’s development parameters: growth and motor performance, hippocampal neuroplasticity, and stress levels.Methods:Pregnant Wistar rats were divided into two groups: sedentary and exercised rats. Exercised pregnant rats were subjected to a strength training protocol (vertical ladder climbing) throughout the gestational period. Male offspring’s body weight, length, and head size were evaluated during the neonatal period (postnatal days [P]2–P21), as well as motor milestones during P0–P8. At P8, a set of male pups were subjected to global hippocampal DNA methylation, hippocampal cell proliferation, and plasma corticosterone concentration.Results:Offspring from trained mothers presented a transient change in body morphometric evaluations, no differences in milestone assessments, enhancement of cell proliferation in the dentate gyrus of the hippocampus, and decreased global hippocampal DNA methylation compared with the offspring from sedentary mothers. Furthermore, strength training during pregnancy did not change the corticosterone concentration of exercised mothers and their offspring.Conclusions:These data indicate that strength training can protect offspring’s development and could impact positively on parameters linked to cognitive function. This study provides a greater understanding of the effects of strength exercise practiced during pregnancy on the offspring’s health.     

Suitability of soccer training drills for endurance training

Recent evidence suggests that certain soccer drills produce exercise intensities suitable for physical conditioning. However, it remains debatable whether soccer drills can provide a sufficiently unified exercise intensity among different players and on repetition of a drill, because movement patterns cannot be externally controlled during soccer drills. Good reliability and low variability of exercise intensity would enable all players to receive an appropriate training stimulus. The purpose of this study was to investigate intersubject variability and intrasubject reliability in exercise intensity during soccer drills. It was hypothesized that soccer drills that involve the highest exercise intensities would demonstrate the lowest intersubject variability and the highest intrasubject reliability. Heart rates of 23 professional soccer players were recorded during a range of soccer training drills. The drills consisted of 2 vs. 2 to 8 vs. 8 normal scoring games and 2 further possession games. Heart rate responses were examined for variability, reliability, and suitability for soccer endurance training. Coefficients of variation across players were less than 3% for all drills. Paired t-tests showed no significant differences in heart rate on repetition of the drills and 95% ratio limits of agreement were 1.8-3.8%. There were no significant correlations between exercise intensity and the statistical measures of variability and reliability. Several drills produced exercise intensities suitable for soccer endurance training with mean heart rate responses ranging from 87-91% HRmax. Soccer drills such as those used in the present study appear to be an adequate substitute for physical training without the ball and thus provide simultaneous skill and fitness training. The increase in training time spent developing technical ability and/or a reduction in total training time required may be useful for soccer teams.