Response of growth and myogenic factors in human skeletal muscle to strength training.

OBJECTIVE: To investigate the response to different strength training techniques of growth and myogenic factors in human skeletal muscle, with particular emphasis on satellite cell (SC) activation. METHODS: 24 volunteers were divided into two groups and performed a 6-week strength training (group A trained with maximum contraction and group B had training combined with maximum contractions, ballistic movement and stretching-shortening cycles). Muscle biopsies were obtained from triceps brachii 3 days before and 7 days after training. For estimating gene expression of insulin-like growth factor (IGF-1), mechano growth factor (MGF), MyoD and myogenin, real-time RT-PCR was performed. RESULTS: In group A, there was an increase in the 1 repeat maximum (1RM), but no change in V(max) (maximum movement velocity) and an increase in MHC (myosin heavy chain) IIa and a decrease in MHC IIx; in group B both 1RM and V(max) increased significantly along with an increase in MHC IIa and a decrease in MHC I. The MGF gene expression increased significantly in both groups (by 1160% and 59%, respectively), and IGF-1 increased only in group A (by 335%). MyoD and myogenin gene expression increased in group A (by 107% and 94%, respectively) but did not change in group B. CONCLUSIONS: Response of growth and myogenic factors occurs during muscular adaptation to a prolonged training, and strength training with different strategies caused different responses with respect to gene expression of these factors. These results suggest that SC activation is involved in the muscular adaptation process to training and might be attributed to MHC isoform transition.

[Balance therapy shoes - a comparative analysis with respect to immediate training effects]. / Sohlenaktivierte therapieschuhe - eine vergleichende trainingsmittelanalyse.

BACKGROUND: Manufacturers attribute specific shoes and sole construction to induce neuromuscular training. Thus injury prevention or rehabilitation from injury is aimed. HYPOTHESIS: H1=Different shoe and sole construction result in different load to the neuromuscular system and postural control. STUDY DESIGN: Controlled laboratory study. METHODS: 10 healthy subjects were tested postural stabilization using a force plate and EMG-recordings. First each person performed three 20 sec single leg unshod stance trial (control condition). Then MBT shoe, Finnamic-Rollenschuh and ReflexControl were applied and tested in a randomized order. RESULTS: No difference in the EMG- activity was detected comparing the barefoot condition with MBT and Finnamic-Rollenschuh (p=0,051-1,000). However with one exception (barefoot M. gastrocnemius. EMG-activity; p=0,110) putting on the ReflexControl shoe increased the EMG-activity relative to all three tested muscles and shoe/barefoot conditions (p=0,000-0,001). Moreover, the ReflexControl shoe led to a highly significantly higher postural sway (p=0,000-0,072), while MBT, Finnamic-Rollenschuh and barefoot conditions were not statistically different (p=0,818-1,000). CONCLUSIONS: This study confirms that during upright stance the ReflexControl shoe is a means for neuromuscular training, while MBT and Finnamic-Rollenschuh simulate barefoot stance.

[Cardiopulmonary responses during high intensity weight training in male handball players]. / Kardiopulmonale Reaktionen während intensiven Krafttrainings bei männlichen Handballspielern.

OBJECTIVE: Strength training has become popular and accepted as part of a well-rounded fitness program. Moreover, resistance training is currently prescribed by many health organizations for improving health and fitness. The purpose of this study was to evaluate the possible influence of high intensity heavy weight training on endurance related parameters. Hence the characteristics of oxygen uptake (VO2) kinetics and the heart rate (HR) kinetics have been assessed during a typical session of strength training in twelve healthy male handball players, aged 20-30 years. METHODS: The oxygen uptake and the heart rate were measured continuously using a portable breath-by-breath exercise system. The training consisted of 4 exercises (squat, bench press, lat pull, and neck press), each performed for ten repetitions at an intensity of 80% of one repetition maximum over a 30-seconds period with a 1:4 work/test ratio. RESULTS: During weight training, the VO2 ranged from 0.8 +/- 0.2 l x min(-1) to 2.4 +/- 0.4 l x min(-1). The lowest values were measured during load, while peak values were reached 40 to 70 seconds after load. Mean (+/- SE) VO2 was 1.22 +/- 0.05 l x min(-1), or 26.5% of the treadmill-determined VO2(max). Mean (+/- SE) HR was 117 +/- 4 beats x min(-1), or 61% of the treadmill-determined HR(max). CONCLUSION: The findings in the present study indicate that high intensity weight training is not able to produce adaptive improvement in cardiovascular function. The physiological responses measured during this experiment provide support to previous studies, that the lack of cardiovascular adaptation may be due to the low percentage of VO2(max)elicited by this form of training.

Overground and walkway ambulation with unilateral hip osteoarthritis: comparison of step length asymmetries and reproducibility of treadmill mounted force plate readings.

The purpose of this study was to analyze and compare the degree of step length asymmetry of patients with hip osteoarthritis during free walking and treadmill ambulation and to determine the reproducibility of treadmill based vertical ground reaction force parameters. Twelve subjects with monoarticular hip osteoarthritis undergoing total hip replacement surgery were assessed preoperatively. The assessed parameters were step length, maximal forces at heel strike and push off minimum force, force inclining and declining rate and relative stance time. The results indicated significant step length differences when comparing overground and treadmill ambulation. The extent of step length asymmetry did not have a consistent expression in different gait conditions. The study demonstrated sufficient intraday reliability for mean GRF measurements. While comparing data from treadmill and walkway locomotion of patients with osteoarthritis it should be taken into account that the amount of step length asymmetry is not identical. Patients with gait disabilities seem to have a somewhat lower level of repeatability and it appears that an increased number of practice or acclimatization trials are necessary.

[Metabolic and cardiovascular response in strength endurance training]. / Metabolische und kardiovaskuläre Beanspruchung im Kraftausdauertraining.

The purpose of this empirical study was: 1 (st): To evaluate the strain in three specifically trained training groups (untrained, athletics and wrestler) by a constant stress (20-RM) in a typically strength endurance training. 2 (nd): To predict the strain in strength endurance training over six sets. The results are: The workload as an objective parameter decreased over the six sets and there was a significant difference between the three different groups. Lactic acid concentration increased in the same way over the sets and there was no statistic difference between the groups. The findings of heart rate, systolic blood pressure, double product and rating of perceived exertion remain clear. There was no healthy risk by usage rate in the set in the three groups.

Different effects on human skeletal myosin heavy chain isoform expression: strength vs. combination training.

Myosin heavy chain (MHC) isoform expression changes with physical training. This may be one of the mechanisms for muscular adaptation to exercise. We aimed to investigate the effects of different strength-training protocols on MHC isoform expression, bearing in mind that alpha- MHC(slow) (newly identified MHC isoform) mRNA may be upregulated in response to training. Twelve volunteers performed a 6-wk strength training with maximum contractions (Max group), and another 12 of similar age performed combination training of maximum contractions and ballistic and stretch-shortening movements (Combi group). Muscle samples were taken from triceps brachii before and after training. MHC isoform composition was determined by SDS-PAGE silver staining, and mRNA levels of MHC isoforms were determined by RT-PCR. In Max group, there was an increase in MHC(2A) (49.4 to 66.7%, P < 0.01) and a decrease in MHC(2X) (33.4 to 19.5%, P < 0.01) after training, although there was no significant change in MHC(slow). In Combi group, there was also an increase in MHC(2A) (47.7 to 62.7%, P < 0.05) and a decrease in MHC(slow) (18.2 to 9.2%, P < 0.05) but no significant change in MHC(2X). An upregulation of alpha-MHC(slow) mRNA was, therefore, found in both groups as a result of training. The strength training with maximum contractions led to a shift in MHC isoform composition from 2X to 2A, whereas the combined strength training produced an MHC isoform composition shift from slow to 2A.

Single- vs. multiple-set strength training in women.

The aim of this study was to compare the effects of single-set and multiple-set strength training in women. Twenty-seven women (aged 20-40 years) with basic experience in strength training were randomly allocated to either a single-set group (n = 9), a 3-set group (n = 9), or a nontraining control group (n = 9). Both training groups underwent a whole-body strengthening program, exercising 2 days a week for 6 weeks. Exercises included bilateral leg extension, bilateral leg curl, abdominal crunch, seated hip adduction/abduction, seated bench press, and lateral pull-down. The single-set group's program consisted of only 1 set of 6-9 repetitions until failure, whereas the multiple-set group trained with 3 sets of 6-9 repetitions until failure (rest interval between sets, 2 minutes). Two times before and 3 days after termination of the training program, subjects were tested for their 1 repetition maximum strength on the bilateral leg extension and the seated bench press machine. Data were analyzed using a repeated-measures analysis of variance, Scheffé tests, t-tests, and calculation of effect sizes. Both training groups made significant strength improvements in leg extension (multiple-set group, 15%; single-set group, 6%; p 0.05). However, in the seated bench press only the 3-set group showed a significant increase in maximal strength (10%). Calculation of effect sizes and percentage gains revealed higher strength gains in the multiple-set group. No significant differences were found in the control group. These findings suggest superior strength gains occurred following 3-set strength training compared with single-set strength training in women with basic experience in resistance training.

[Strength training with superimposed vibrations]. / Krafttraining unter Vibrationseinwirkung.

To examine the effects of strength training with superimposed vibrations ten subjects trained over a period of six weeks (three sessions per week) one leg with back squats and superimposed vibrations and the other leg with traditional squats. In each training session participants performed 4 sets with 8-12 repetitions. Before and after the training period maximum strength and rate of force development were measured. The results show that both training modes induced comparable and statistical significant increases in maximum strength (vibration training +6.5%, traditional training +6.2%. The slight increases in rate of force development in both groups didn't reach statistical significance. As a consequence it seems that strength training with superimposed vibrations for the leg extensor chain is not superior to a traditional training mode.

Kinematics and electromyography of lower limb muscles in overground and treadmill running.

Treadmills are often used in research to analyse kinematic and physiological variables. The success of transfering the results to overground running depends on the comparability of the values between the two situations. The aim of the present study was to compare the kinematics and muscle activities in overground and treadmill running. Ten male physical education students with experience in treadmill running were asked to run with a speed of 4.0 and 6.0 m/s both overground and on a Woodway treadmill. The 3D-kinematics of the limbs were studied using a two camera video tracking system. Additionally the surface EMG of six lower limb muscles and the pattern of ground contact of the right foot was registered. Both the activities of the leg muscles and several kinematic variables showed systematic changes from overground to treadmill running. On the treadmill the subjects favoured a type of running that provided them with a higher level of security. The swing amplitude of the leg, the vertical displacement and the variance in vertical and horizontal velocity were lower in treadmill running. The angle between shoe sole and ground at foot impact was also lower and the forward lean of the upper body was higher in running on the treadmill compared with the overground mode. Most of the subjects reduced their step length and increased stride frequency in treadmill running. Furthermore, the contact time in treadmill running was shorter than for overground running. The above mentioned kinematic variables were significantly different (p < 0.05). The EMG patterns of the leg muscles were generally similar between overground and treadmill modes, but some minor differences could consistently be identified.

[Modification of reactivity by rhythmic neuromuscular stimulation]. / Beeinflussung der Reaktivität durch die rhythmische neuromuskuläre Stimulation (RNS).

The rhythmical neuromuscular stimulation (RNS) by Nasarov is a new method for optimizing performance. By transferring mechanical vibration to the tendomuscular system better coordination of peripheral and central nervous system could be achieved. A study with twelve healthy students of physical education dealt with the question of the effects of RNS on drop jumps. After 12 minutes application of RNS the performance drastically decreased. Jumping height lowered and ground contact time increased. Recordings of EMG revealed corresponding alterations in muscle activity, such occurring in overload situations. Plastic deformation of tendon collagen and neuromuscular adaptation as stiffness-reduction of gamma-modulation is discussed.

[Development of joint mobility by rhythmic neuromuscular stimulation]. / Entwicklung der Gelenkbeweglichkeit durch die rhythmische neuromusckuläre Stimulation (RNS).

According to Nasarov an outstanding improvement of flexibility could be reached by using the rhythmical neuromuscular stimulation (RNS). For proving this statement a study with 112 healthy fitness sportsmen and women was performed for three weeks at chest muscles. Overall, there was no clear advantage of RNS versus static stretch shown. However, it exists a dependence of improving flexibility by static stretch at simultaneous strength training. Persons who perform strength training obtain a higher improvement in flexibility than others. Using RNS the results in reaching high range of motions are independent of strength training and comparable to static stretch at simultaneous strength training. The results were discussed by a higher rate of biosynthesis induced by strength training respectively by the eccentric load of RNS.

Frequency variations of strength training sessions triggered by the phases of the menstrual cycle.

The aim of the study was to compare the effects of two different models of altering the frequency of strength training sessions of females. The "regular training" (RT) consisted of one training unit every third day over the whole menstrual cycle. The "menstrual cycle triggered training" (MCTT) was characterized by workouts every second day in the follicular and about once per week during the luteal phase. In order to increase maximal strength (MS) the participants performed 3 sets with 12 reps each. Endogenous processes were controlled by measurements of body-temperature, control of the luteinizing-hormone peak, and by analysing serum hormone (estradiol, progesterone, testosterone, and cortisol) and sexual hormone binding globulin (SHBG) levels. MS and muscle cross-sectional area (MCA) of the quadriceps femoris were investigated. The result of the MCTT showed a clear increase in the MS of 32.6% compared to 13.1% by the RT. Significant MCTT-induced MS increase was observed during the second menstrual cycle. The ratio of MS/MCA increased by 10.5% (RT) and 27.6% (MCTT). Despite a wide interindividual variability, all subjects showed higher strength adaptations by MCTT. Additionally, we found significant correlations between different force parameters and the accumulation of estradiol. It was concluded that the MCTT seems to be more efficient compared to RT.

[Specific methods of strength training also in rehabilitation]. / Spezifische Krafttrainingsmethoden auch in der Rehabilitation.

Until now only minor attention was given to the importance of strength training methods as part of rehabilitation. Even though there are numerous methods in physical therapy which can, under certain limitations, be summed up as a type of strength training, a differentiated use of training methods which are recognized in sport has not been accepted. However, especially the search for a rapid rehabilitation of the body's performance capability brings up the question about effective training methods. In the following paper the physiological conditions are discussed first, on whose basis the motor requirement "strength" has been structured. This results in consequences for the practical training. For each strength component been introduced, practical suggestions for a strength training are given.

Reproducibility of electromyographic patterns in stretch-shortening type contractions.

Within a set of repeated measurements, 12 male subjects performed the following types of muscle contraction: (1) running at constant velocity (12 km.h-1); (2) one-leg hopping at the frequency preferred; (3) both-legs hopping at the frequency preferred; (4) drop jumps from a height of 0.40 m. The surface electromyographs (EMG) from the left and right legs were recorded, together with the averaged signals from vertical ground reaction forces and angular displacement of the ankle joint. Reliability coefficients for the day to day and the week to week comparison were calculated. In addition, on any one test day the positions of the electrodes were systematically changed. The analysis of various EMG parameters (integrated-EMG) revealed high coefficients for both comparisons as well as for the total set of measurements. Qualitative comparisons of the EMG showed a high reproducibility of the shape of the patterns. If the relative position of the electrodes with respect to the belly of the muscle is changed, the amplitudes of the EMG recordings are markedly reduced. It is concluded that surface EMG is a reliable method for studies of the neuromuscular system. On the basis of the data presented, it is suggested that the term "reliability" should be replaced by the term "reproducibility" in order to cover both the aspect of the relative stability plus the aspects of linear changes and the scattering of the data in repeated measurements.

Interaction between man and shoe in running: considerations for a more comprehensive measurement approach.

Man-shoe-surface interaction in running is a complex phenomenon, and its investigation gives specific requirements for the measuring system. This study was designed to make an effort to develop a methodology for measuring the interaction between the first two components (man and shoe) under normal heel running conditions both on the force plate and on an asphalt road. The force plate system consisted of a series of 1.5-m long plates with a total length of 12 m. This allowed recordings of several natural ground contact phases in one run. By repeating the runs several times at constant velocity (3 m X s-1 and 5 m X s-1), altogether 10-30 Fz and Fx force curves could be obtained for further computerized averaging. The running shoes were equipped with special heel and toe contact sensors, which were used for recordings of even more cycles at constant velocity on the road running conditions. Telemetered EMG technique was employed to examine the response of the selected lower extremity muscles on the varying shoe and running velocity conditions. The results indicated preliminarily that the changes in ground reaction forces were more velocity than shoe (hard/soft) dependent and that EMG activation patterns were muscle specific with regard to preinnervation and impact and push-off phases for the gastrocnemius, rectus femoris, vastus lateralis, and tibialis anterior muscles. Although the actual measurements were not yet designed for comprehensive recording of each parameter, the results obtained suggest that the major leg extensor muscles change their activation patterns with the varying impact load conditions.(ABSTRACT TRUNCATED AT 250 WORDS)

Compensatory movements following gait perturbations: changes in cinematic and muscular activation patterns.

The present study was designed to investigate the neuronal control and biomechanical effects of stumbling reactions. To induce these perturbations, a specially prepared treadmill was used which allowed rapid and powerful changes of treadmill speed. EMG recordings of leg muscles were related to cinematic movement patterns. Following an accelerating impulse, the standing leg was displaced in a posterior direction compared with normal gait, with a premature touchdown of the contralateral, swinging leg, forward of the body axis. This was associated with simultaneous activation of the gastrocnemius and biceps femoris of the ipsilateral and the tibialis anterior muscles of the contralateral leg. Following deceleration, the standing leg was displaced in an anterior direction and the contralateral swinging leg touched the ground prematurely behind the body axis. This was associated with activation of the ipsilateral tibialis anterior and rectus femoris and contralateral tibialis anterior muscles. In both conditions, the activation of the lower leg muscles on both sides occurred with a latency of 60-70 ms, monosynaptic responses being absent. In both cases, early touchdown was associated with a forward extension of the arm. It is concluded that the EMG responses are mediated by a polysynaptic spinal pathway to keep the body center of gravity constant and to prevent falling.

Regulation of muscle stiffness in human locomotion.

The tension development of the triceps surae muscle was analyzed during the stance phase of locomotion at different speeds with respect to its electrical activation and its lengthening and shortening behavior. The main point was the coincidence of maximal dorsiflexion, maximal Achilles tendon tension, transition from amortization to acceleration phase, and projection of the center of gravity to the supporting leg. It is concluded that the stiffness regulation needed for load compensation after impact and pushing off at the end of stance phase depends on modulation and enhancement of a centrally programmed muscle activation by a segmental stretch reflex activity.

Interaction between pre-activity and stretch reflex in human triceps brachii during landing from forward falls.

1. Electromyographic (e.m.g.) profiles of proximal arm muscles were studied in human subjects falling forward onto a platform. 2. The stretching of the triceps lasted 200-300 msec for deep falls, and immediately after impact angular velocities of the elbow joint up to 1000 degrees sec-1 were reached. 3. For angles of fall between 50 and 90 degrees, more than half of the subjects exhibited marked short-latency e.m.g. responses of the triceps brachii. Such responses began 20-30 msec after touchdown, arising from a more or less plateau-like activity which started about 130 msec before impact. In some cases distinct later responses were found, the second peak having a latency of 60-80 msec after touchdown. 4. The early e.m.g. response even appeared when the subject was blindfolded and when the depth of the fall was randomly varied. 5. It is concluded that both the pre-existing activity and the spinal stretch reflex contribute significantly to the over-all activity of the triceps during stretch after impact.