Dietmar Schmidtbleicher

Effects of random whole-body vibration on postural control in Parkinson's disease.

We investigated spontaneous effects of random whole-body vibration (rWBV) on postural control in Parkinsonian subjects. Effects were examined in biomechanical tests from a total of 52 patients divided equally into one experimental and one control group. Postural control was tested pre- and post-treatment in two standardized conditions (narrow standing and tandem standing). The intervention was based on rWBV (y: 3 mm, f: 6 Hz 1 Hz/sec) consisting of 5 series lasting 60 seconds each. The main findings from this study were that (1) rWBV can improve postural stability in Parkinsons disease (PD) spontaneously (2) these effects depend on the test condition. Based on the results of this study, rWBV can be regarded as an additional device in physical therapy in PD.

Effects of different periodization models on rate of force development and power ability of the upper extremity.

Hartmann, H, Bob, A, Wirth, K, and Schmidtbleicher, D. Effects of different periodization models on rate of force development and power ability of the upper extremity. J Strength Cond Res 23(7): 1921-1932, 2009-The purpose of our study was to compare the effects of 2 different periodization models on strength and power variables under dynamic and static conditions in the bench press. Participants of the experimental groups were male sport students experienced in weight training (age: 23.98 ± 3.14 yr). Subjects were tested for the 1 repetition maximum (1RM) in the bench press, maximal movement velocity (Vmax) in the bench press throw (16.9 kg), maximal voluntary contraction (MVC), and maximal rate of force development (MRFD) in 90° elbow and shoulder angle in the isometric bench press. According to their 1RM, subjects were parallelized and assigned to 1 of either 2 training groups: strength-power periodization (SPP, n = 13) or daily undulating periodization (DUP, n = 14). Subjects trained for 14 weeks, 3 days per week. In the strength-power sessions, both groups were instructed to lift the weight as explosively as possible. In addition, a control group (n = 13) was used for comparison. One repetition maximum and Vmax improved significantly through training (p ≤ 0.05), with no significant changes in MVC and MRFD. Experimental groups showed no significant group differences in any variable. The results indicate that, in short-term training using previously trained subjects, no differences in 1RM and power are seen between DUP and SPP. As used in our undulating regime, additional training in strength endurance could lead to exhaustion effects and furthermore does not provide an adequate training stimulus for power because of its low training intensity. In spite of this, according to the present findings, it has no negative effect on the application of a neural stimulus that is needed for a strength-power session if adequate regeneration time between workouts is guaranteed.

Influence of squatting depth on jumping performance.

Abstract Hartmann, H, Wirth, K, Klusemann, M, Dalic, J, Matuschek, C, and Schmidtbleicher, D. Influence of squatting depth on jumping performance. J Strength Cond Res 26(12): 3243–3261, 2012—It is unclear if increases in 1 repetition maximum (1RM) in quarter squats result in higher gains compared with full depth squats in isometric force production and vertical jump performance. The aim of the research projects was to compare the effects of different squat variants on the development of 1RM and their transfer effects to Countermovement jump (CMJ) and squat jump (SJ) height, maximal voluntary contraction (MVC), and maximal rate of force development (MRFD). Twenty-three women and 36 men (mean age: 24.11 ± 2.88 years) were parallelized into 3 groups based on their CMJ height: deep front squats (FSQ, n = 20), deep back squats (BSQ, n = 20), and quarter back squats (BSQ¼, n = 19). In addition, a control group (C, n = 16) existed (mean age: 24.38 ± 0.50 years). Experimental groups trained 2 d·wk−1 for 10 weeks with a strength-power block periodization, which produced significant (p ⩽ 0.05) gains of the specific squat 1RM. The FSQ and BSQ attained significant (p ⩽ 0.05) elevations in SJ and CMJ without any interaction effects between both groups (p ≥ 0.05). The BSQ¼ and C did not reveal any significant changes of SJ and CMJ. The FSQ and BSQ had significantly higher SJ scores over C (p ⩽ 0.05). The BSQ did not feature any significant group difference to BSQ¼ (p = 0.116) in SJ, whereas FSQ showed a trend toward higher SJ heights over BSQ¼ (p = 0.052). The FSQ and BSQ presented significantly (p ⩽ 0.05) higher CMJ heights over BSQ¼ and C. Posttest in MVC and MRFD demonstrated no significant changes for BSQ. Significant declines in MRFD for FSQ in the right leg (p ⩽ 0.05) without any interaction effects for MVC and MRFD between both FSQ and BSQ were found. Training of BSQ¼ resulted in significantly (p ⩽ 0.05) lower MRFD and MVC values in contrast to FSQ and BSQ. Quarter squat training elicited significant (p ⩽ 0.05) transfer losses into the isometric maximal and explosive strength behavior. These findings therefore contest the concept of superior angle-specific transfer effects. Deep front and back squats guarantee performance-enhancing transfer effects of dynamic maximal strength to dynamic speed-strength capacity of hip and knee extensors compared with quarter squats.

Long-term strength training effects on change-of-direction sprint performance.

Abstract Keiner, M, Sander, A, Wirth, K, and Schmidtbleicher, D. Long-term strength training effects on change-of-direction sprint performance. J Strength Cond Res 28(1): 223–231, 2014—The requirement profiles for sports such as soccer, football, tennis, and rugby demonstrate the importance of strength and speed-strength abilities, in addition to other conditional characteristics. During a game, the athletes complete a large number of strength and speed-strength actions. In addition to the linear sprints, athletes perform sprints while changing the direction (change-of-direction sprint [COD]). Therefore, this study aims to clarify the extent to which there is a strength training intervention effect on COD. Further, this investigation analyzes the possible correlations between the 1-Repetition Maximum/body mass (SREL) in the front and back squats and COD. The subjects (n = 112) were at pretest between 13 and 18 years of age and were divided into 2 groups with 4 subgroups (A = under 19 years of age, B = under 17 years of age, and C = under 15 years of age). For approximately 2 years, 1 group (control group [CG]) only participated in routine soccer training, and the other group (strength training group [STG]) participated in an additional strength training program with the routine soccer training. Additionally, the performances in the COD of 34 professional soccer players of the first and second divisions in Germany were measured as a standard of high-level COD. For the analysis of the performance development within a group and pairwise comparisons between 2 groups, an analysis of variance with repeated measures was calculated with the factors group and time. Relationships between the COD and SREL were calculated for the normal distributed data using a plurality of bivariate correlations by Pearson. Our data show that additional strength training over a period of 2 years significantly affects the performance in the COD. The STG in all subcohorts reached significantly (p < 0.05) faster times in the COD than did the CG. The STG amounted up to 5% to nearly 10% better improvements in the 10-m sprint times compared with that of the CG. Furthermore, our data show significant (p < 0.05) moderate to high correlations (r = −0.388 to −0.697) between the SREL and COD. Our data show that a long-term strength training improves the performance of the COD. Therefore, a long-term resistance training is recommended as early as in childhood and adolescence.

Influence of a 2-year strength training programme on power performance in elite youth soccer players

Abstract In soccer, strength, power and speed are very important because of the large number of power actions performed during the game. Therefore, the aim of this study was to examine the influence of periodised strength training for power performance more than 2 years. In this study, 134 elite youth soccer players were recruited from two youth training centres. The cohorts were arranged as follows: A (under 19 years), B (under 17 years) and C (under 15 years). The participants in each cohort were divided into two groups. One group (Strength training group [STG]) was subjected to regular soccer training in addition to strength training twice a week for 2 years. The other group (Control group [CG]) completed only the regular soccer training. The strength training was periodised with hypertrophy and intramuscular coordination blocks. For strength training, both the front squat and the back squat were performed once a week. The subjects were tested on the one-repetition maximum (1RM) of the front and back squat and a linear sprint over 30 m. There was significantly better performance from the STG on 1RM (p <0.001). In the sprint, the STG displayed significantly better improvements (p <0.05 to p <0.001) of up to 6%. The effects of strength training are reflected in the sprint performance. Therefore, it seems beneficial for youth to perform strength training to exploit the reserve capacity in sprint performances.

Proprioceptive and Sensorimotor Performance in Parkinson's Disease

We explored the effects of random whole-body vibration on leg proprioception in Parkinsons disease (PD). In earlier studies it was found that this treatment leads to improved postural control in these patients. Thus, one could speculate that these effects result from modified proprioceptive capabilities. Twenty-eight PD patients were subdivided in one experimental and one control group. Proprioceptive performance was analyzed using a tracking task basing on knee extension and flexion movements. Treatment consisted of 5 series of random whole-body vibration taking 60 seconds each. Control subjects had a rest period instead. Prominent over- and undershooting errors were found in both groups representing proprioceptive impairments. No significant differences became evident, however, either between pre- and post-tests or between experimental and control group. One might therefore conclude that spontaneous improvements in postural control are not directly connected with proprioceptive changes. Nevertheless, one also should keep in mind the general aspects and difficulties of analyzing proprioception.

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 Vmax (maximum movement velocity) and an increase in MHC (myosin heavy chain) IIa and a decrease in MHC IIx; in group B both 1RM and Vmax 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.

Training effects of two different unstable shoe constructions on postural control in static and dynamic testing situations

OBJECTIVE The aim of this study was to compare training effects on postural control using two different unstable shoe constructions. SUBJECTS AND SETTING Twenty-nine healthy subjects participated in this study and were randomly divided into three groups. Two experimental groups (10 subjects in each group) were assigned to a 6 week training program of specific sensorimotor exercises with unstable shoe constructions, one group using MBT(®) shoes and one group wearing Reflex Control(®) shoes (RC). Subjects in the control group (9 subjects) did not perform balance training. MAIN OUTCOME MEASURES Postural control was measured in one-leg stance in two testing conditions. We recorded postural sway on a force plate (static testing situation) and displacements of a moveable platform (dynamic testing situation) before and after the training period. RESULTS There were no effects of training with unstable shoe constructions on postural sway in the static testing condition (for comparison of groups: p = 0.990 and p = 0.119). However, the RC group showed statistically significant improvements in the dynamic testing situation (p = 0.014 compared to control subjects). In the MBT group improvements were not significantly different in comparison to control group (p = 0.518). CONCLUSIONS Our results indicate that exercises using unstable shoe constructions, particularly the RC, improve postural control only in dynamic conditions.

Effects of functional exercises in the warm-up on sprint performances.

Abstract Sander, A, Keiner, M, Schlumberger, A, Wirth, K, and Schmidtbleicher, D. Effects of functional exercises in the warm-up on sprint performances. J Strength Cond Res 27(4): 995–1001, 2013—The process of warming up prepares athletes for subsequent stress and increases their level of performance. Functional exercises are often included in warm-up programs for power sports, although a positive effect of functional exercises has not been confirmed. The aim of this study was to measure a possible effect of functional exercises on sprint performance included in a warm-up program. A total of 121 elite youth soccer players between 13 and 18 years of age participated in this study and performed 2 different warm-up programs. The first program (NWP) consisted of 5 minutes of nonspecific running, coordination exercises, stretching, and acceleration runs. The second program (WPS) was the same with additional functional exercises. The subjects were tested performing linear sprints of approximately 30 m and change-of-direction sprints of approximately 10 m. The t-test for dependent samples showed significant differences between the groups for each segment of the linear sprint (p < 0.01 for 5 m; p < 0.001 for 10, 15, 20, 25, and 30 m); however, the effect sizes are small. Also, in the change-of-direction sprint, the t-test showed significant differences between the groups (p < 0.01 for 10 m left, 10 m right; p < 0.001 for 5 m right). These effect sizes are also small. In the change-of-direction sprint time for 5 m left, the data showed no significant differences between the groups. The results show no effects of functional exercises on sprint performance that are implemented in addition to a general warm-up. It appears that a general warm-up program, such as the NWP, generates sufficient activation of the performance-limiting muscles for sprint performance. Functional exercises did not lead to a supplemental activation with a positive effect on sprint performance. Therefore, a warm-up for sprint performance should contain nonspecific running, coordination exercises, stretching exercises, and acceleration runs. These components lead to sufficient activation of the muscles involved in sprint performance. Coaches should use the limited time available for warm-up to work efficiently. The recommendation for warm-up is to pass on functional exercises that have no additional effect in enhancing performance.

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.