Muscular performance characterization in athletes: a new perspective on isokinetic variables

Background:

Isokinetic dynamometry allows the measurement of several variables related to muscular performance, many of which are seldom used, while others are redundantly applied to the characterization of muscle function.

Objectives:

The present study aimed to establish the particular features of muscle function that are captured by the variables currently included in isokinetic assessment and to determine which variables best represent these features in order to achieve a more objective interpretation of muscular performance.

Method:

This study included 235 male athletes. They performed isokinetic tests of concentric knee flexion and extension of the dominant leg at a velocity of 60º/s. An exploratory factor analysis was performed.

Results:

The findings demonstrated that isokinetic variables can characterize more than muscle torque production and pointed to the presence of 5 factors that enabled the characterization of muscular performance according to 5 different domains or constructs.

Conclusions:

The constructs can be described by torque generation capacity; variation of the torque generation capacity along repetitions; movement deceleration capacity; mechanical/physiological factors of torque generation; and acceleration capacity (torque development). Fewer than eight out of sixteen variables are enough to characterize these five constructs. Our results suggest that these variables and these 5 domains may lead to a more systematic and optimized interpretation of isokinetic assessments.     

Kinesio Taping effects on knee extension force among soccer players

Background:

Kinesio Taping (KT) is widely used, however the effects of KT on muscle activation and force are contradictory.

Objective:

To evaluate the effects of KT on knee extension force in soccer players.

Method:

This is a clinical trial study design. Thirty-four subjects performed two maximal isometric voluntary contractions of the lower limbs pre, immediately post, and 24 hours after tape application on the lower limbs. Both lower limbs were taped, using K-Tape and 3M Micropore tape randomly on the right and left thighs of the participants. Isometric knee extension force was measured for dominant side using a strain gauge. The following variables were assessed: peak force, time to peak force, rate of force development until peak force, time to peak rate of force development, and 200 ms pulse.

Results:

There were no statistically significant differences in the variables assessed between KT and Micropore conditions (F=0.645, p=0.666) or among testing sessions (pre, post, and 24h after) (F=0.528, p=0.868), and there was no statistical significance (F=0.271, p=0.986) for interaction between tape conditions and testing session.

Conclusion:

KT did not affect the force-related measures assessed immediately and 24 hours after the KT application compared with Micropore application, during maximal isometric voluntary knee extension.     

Strength deficits of the shoulder complex during isokinetic testing in people with chronic stroke

OBJECTIVES:

To examine the strength deficits of the shoulder complex after stroke and to characterize the pattern of weakness according to type of movement and type of isokinetic parameter.

METHOD:

Twelve chronic stroke survivors and 12 age-matched healthy controls had their shoulder strength measured using a Biodex isokinetic dynamometer. Concentric measures of peak torque and work during shoulder movements were obtained in random order at speeds of 60°/s for both groups and sides. Type of movement was defined as scapulothoracic (protraction and retraction), glenohumeral (shoulder internal and external rotation) or combined (shoulder flexion and extension). Type of isokinetic parameter was defined as maximum (peak torque) or sustained (work). Strength deficits were calculated using the control group as reference.

RESULTS:

The average strength deficit for the paretic upper limb was 52% for peak torque and 56% for work. Decreases observed in the non-paretic shoulder were 21% and 22%, respectively. Strength deficit of the scapulothoracic muscles was similar to the glenohumeral muscles, with a mean difference of 6% (95% CI -5 to 17). Ability to sustain torque throughout a given range of motion was decreased as much as the peak torque, with a mean difference of 4% (95% CI -2 to 10).

CONCLUSIONS:

The findings suggest that people after stroke might benefit from strengthening exercises directed at the paretic scapulothoracic muscles in addition to exercises of arm elevation. Clinicians should also prescribe different exercises to improve the ability to generate force and the ability to sustain the torque during a specific range of motion.     

Longitudinal assessment of grip strength using bulb dynamometer in Duchenne Muscular Dystrophy

BACKGROUND:

Grip strength is used to infer functional status in several pathological conditions, and the hand dynamometer has been used to estimate performance in other areas. However, this relationship is controversial in neuromuscular diseases and studies with the bulb dynamometer comparing healthy children and children with Duchenne Muscular Dystrophy (DMD) are limited.

OBJECTIVE:

The evolution of grip strength and the magnitude of weakness were examined in boys with DMD compared to healthy boys. The functional data of the DMD boys were correlated with grip strength.

METHOD:

Grip strength was recorded in 18 ambulant boys with DMD (Duchenne Group, DG) aged 4 to 13 years (mean 7.4±2.1) and 150 healthy volunteers (Control Group, CG) age-matched using a bulb dynamometer (North Coast- NC70154). The follow-up of the DG was 6 to 33 months (3-12 sessions), and functional performance was verified using the Vignos scale.

RESULTS:

There was no difference between grip strength obtained by the dominant and non-dominant side for both groups. Grip strength increased in the CG with chronological age while the DG remained stable or decreased. The comparison between groups showed significant difference in grip strength, with CG values higher than DG values (confidence interval of 95%). In summary, there was an increment in the differences between the groups with increasing age. Participants with 24 months or more of follow-up showed a progression of weakness as well as maintained Vignos scores.

CONCLUSIONS:

The amplitude of weakness increased with age in the DG. The bulb dynamometer detected the progression of muscular weakness. Functional performance remained virtually unchanged in spite of the increase in weakness.     

Correlation between handgrip and isokinetic strength of shoulder muscles in elite sitting volleyball players

The aim of this study was to examine the relationships between isometric handgrip (HG) strength and isokinetic strength data of the glenohumeral rotator muscles. Twelve (Female = 50%) Brazilian Sitting Volleyball (SV) national team players volunteered. Measures of maximal grip strength were obtained by a HG dynamometer Jamar® and isokinetic measures of peak torque (PT) and total work (TW) during shoulder rotations movements were obtained with a Biodex isokinetic dynamometer at speed of 60°/s and 180°/s. Pearson correlation coefficients between isometric HG and isokinetic strength data ranged between 0.23 and 0.72 for the PT and between 0.3 and 0.76 for the isokinetic TW. Results presented positive relationships between HG isometric strength and isokinetic strength of external rotators of the shoulder in SV players. We can suggest that in the absence of isokinetic dynamometers, HG isometric strength measurements could be used to measure strength levels of the external rotator muscles of elite SV players’ shoulder, particularly in the TW values.     

Intra and inter-rater reliability study of pelvic floor muscle dynamometric measurements

OBJECTIVE:

The aim of this study was to evaluate the intra and inter-rater reliability of pelvic floor muscle (PFM) dynamometric measurements for maximum and average strengths, as well as endurance.

METHOD:

A convenience sample of 18 nulliparous women, without any urogynecological complaints, aged between 19 and 31 (mean age of 25.4±3.9) participated in this study. They were evaluated using a pelvic floor dynamometer based on load cell technology. The dynamometric evaluations were repeated in three successive sessions: two on the same day with a rest period of 30 minutes between them, and the third on the following day. All participants were evaluated twice in each session; first by examiner 1 followed by examiner 2. The vaginal dynamometry data were analyzed using three parameters: maximum strength, average strength, and endurance. The Intraclass Correlation Coefficient (ICC) was applied to estimate the PFM dynamometric measurement reliability, considering a good level as being above 0.75.

RESULTS:

The intra and inter-raters'' analyses showed good reliability for maximum strength (ICC_intra-rater1=0.96, ICC_intra-rater2=0.95, and ICC_inter-rater=0.96), average strength (ICC_intra-rater1=0.96, ICC_intra-rater2=0.94, and ICC_inter-rater=0.97), and endurance (ICC_intra-rater1=0.88, ICC_intra-rater2=0.86, and ICC_inter-rater=0.92) dynamometric measurements.

CONCLUSIONS:

The PFM dynamometric measurements showed good intra- and inter-rater reliability for maximum strength, average strength and endurance, which demonstrates that this is a reliable device that can be used in clinical practice.     

等速运动装置在肩关节术后康复中的应用

目的:观察应用等速运动装置对肩关节手术后的患者进行康复训练的疗效。方法:应用等速运动装置的连续被动运动程序、助力运动程序和等速向心收缩程序对10名肩关节术后患者进行促进肩关节屈曲角度和增强肩关节屈曲肌力的训练,每周3次,共训练12—24次。结果:训练后患者患侧肩关节屈曲角度增加(P<0.01),训练后患侧肩关节屈肌肌力增强(P<0.01),但与健侧对比,关节活动度和肌力仍遗留明显差距(P<0.05)。结论:等速运动装置可用于肩关节术后康复训练,对改善关节活动度和增强肌力均有显著疗效。     

等速肌力训练对偏瘫患者上肢运动功能恢复的影响

目的:研究等速肌力训练结合偏瘫肢体综合运动疗法对脑卒中偏瘫患者上肢运动功能恢复的影响。方法:选择恢复期脑卒中偏瘫患者40例,随机分为观察组和对照组各20例。对照组接受常规偏瘫肢体综合运动疗法、作业治疗、ADL训练以及传统物理因子治疗等对症治疗;观察组在此基础上另外配合偏瘫上肢等速肌力训练。干预前后分别使用BIODEX system-3等速肌力测试系统检测肩屈伸生物力学指标,Fugl-Meyer运动功能量表(FMA)评分上肢部分,改良Ashworth痉挛量表评分,NRS数字疼痛量表(NRS)评分来评定患侧上肢的运动功能、肌张力及疼痛。结果:经过3周治疗,2组患者肩屈伸生物力学指标、FMA上肢运动功能评分、NRS疼痛评分均较前有显著改善,且观察组优于对照组(P0.05);2组患者肌张力均较前改善,但治疗前后差异无统计学意义。结论:等速肌力训练可增强脑卒中偏瘫患者肩关节屈伸肌力,且不会加剧肌肉痉挛和肩关节疼痛,有效促进脑卒中偏瘫患者上肢功能的改善。     

Risk factors and injury prevention in elite athletes: a descriptive study of the opinions of physical therapists,doctors and trainers

Background

Musculoskeletal injuries occur frequently in elite athletes. Understanding what professionals who work with patients with sports injuries think about prevention has been suggested as an important aspect to improve the effectiveness of programs to prevent sports injuries.

Objectives

To describe and characterize the opinions of physical therapists, physicians and trainers on ''risk factors'' and ''prevention of injury'' in elite athletes.

Method

This is a qualitative study with semi-structured interviews with members of the medical and technical department of the Brazilian delegation who participated in the Pan American Games of Guadalajara 2011. The interview was conducted using two questions: 1) "What do you think can cause injuries in athletes participating in your sport?" 2) "What do you do to prevent injuries in your sport?" The interviews were analyzed in two stages, the identification of thematic units, followed by the categorization and grouping of thematic units.

Results

We interviewed a total of 30 professionals. Regarding question 1, the main factors attributed as responsible for injury were over-training and incorrect sports techniques. Regarding question 2, the main reported strategies used to prevent injuries were muscle strengthening, nutritional counseling and guidance.

Conclusions

The main factors affecting the appearance of lesions were over-training, incorrect sports technique, inadequate nutrition and factors related to the athlete''s behavior. The main injury prevention strategies were muscle strengthening, nutritional counseling and guidance.     

Selective hypertrophy of the quadriceps musculature after 14 weeks of isokinetic and conventional resistance training

One of the fundamental adaptations observed with resistance training (RT) is muscle hypertrophy. Conventional and isokinetic machines provide different forms of mechanical stress, and it is possible that these two training modes could promote differing degrees of hypertrophic adaptations. There is a lack of data comparing the selective hypertrophy of the quadriceps musculature after training with a conventional knee extension machine versus an isokinetic machine. The purpose of this study was to evaluate the selective hypertrophy of the quadriceps musculature and knee extension maximal isometric torque after 14 weeks of conventional versus isokinetic RT. Thirty-five men were assigned to three groups: control group and training groups (conventional and isokinetic) performed three sets of unilateral knee extensions per session with a progressive loading scheme twice a week. Prior to and following the intervention, maximal isometric knee extensor torque was measured using an isokinetic dynamometer, and muscle thickness (MT) of quadriceps femoris muscles was assessed via ultrasound. The results indicated non-uniform changes in MT between the muscles that comprise the quadriceps femoris group. For the conventional group, significantly greater increases in rectus femoris thickness were evident versus all other quadriceps muscles (14%). For the isokinetic group, increases in RF thickness (11%) were significantly greater in comparison with the vastus intermedius only. Although the muscle thickness did not increase for all the quadriceps femoris muscles, the relative rectus femoris adaptation suggested a selective hypertrophy favouring this portion.     

Effect of upper extremity proprioceptive neuromuscular facilitation combined with elastic resistance bands on respiratory muscle strength: a randomized controlled trial

Background

Elastic resistance bands (ERB) combined with proprioceptive neuromuscular facilitation (PNF) are often used in resistance muscle training programs, which have potential effects on peripheral muscle strength. However, the effects of the combination of ERB and PNF on respiratory muscle strength warrant further investigation.

Objectives

The assessment of the effects of PNF combined with ERB on respiratory muscle strength.

Method

Twenty healthy, right-handed females were included. Subjects were randomized to either the resistance training program group (TG, n=10) or the control group (CG, n=10). Maximal expiratory pressure (MEP) and inspiratory pressure (MIP) were measured before and after four weeks of an upper extremity resistance training program. The training protocol consisted of upper extremity PNF combined with ERB, with resistance selected from 1 repetition maximum protocol.

Results

PNF combined with ERB showed significant increases in MIP and MEP (p<0.05). In addition, there were significant differences between the TG and CG regarding ∆MIP (p=0.01) and ∆MEP (p=0.04).

Conclusions

PNF combined with ERB can have a positive impact on respiratory muscle strength. These results may be useful with respect to cardiopulmonary chronic diseases that are associated with reduced respiratory muscle strength.     

Critical review of the impact of core stability on upper extremity athletic injury and performance

BACKGROUND:

Programs designed to prevent or rehabilitate athletic injuries or improve athletic performance frequently focus on core stability. This approach is based upon the theory that poor core stability increases the risk of poor performance and/or injury. Despite the widespread use of core stability training amongst athletes, the question of whether or not sufficient evidence exists to support this practice remains to be answered.

OBJECTIVES:

1) Open a dialogue on the definition and components of core stability. 2) Provide an overview of current science linking core stability to musculoskeletal injuries of the upper extremity. 3) Provide an overview of evidence for the association between core stability and athletic performance.

DISCUSSION:

Core stability is the ability to control the position and movement of the trunk for optimal production, transfer, and control of forces to and from the upper and lower extremities during functional activities. Muscle capacity and neuromuscular control are critical components of core stability. A limited body of evidence provides some support for a link between core stability and upper extremity injuries amongst athletes who participate in baseball, football, or swimming. Likewise, few studies exist to support a relationship between core stability and athletic performance.

CONCLUSIONS:

A limited body of evidence exists to support the use of core stability training in injury prevention or performance enhancement programs for athletes. Clearly more research is needed to inform decision making when it comes to inclusion or emphasis of core training when designing injury prevention and rehabilitation programs for athletes.     

The influence of resistance exercise with emphasis on specific contractions (concentric vs. eccentric) on muscle strength and post-exercise autonomic modulation: a randomized clinical trial

Background

Compared to eccentric contractions, concentric contractions result in higher cardiovascular stress. However, we do not know how these two types of contractions influence cardiac autonomic modulation during the post-exercise recovery period.

Objective

to compare the effect of resistance training that is performed with concentric vs. eccentric emphasis on muscle strength and on post-exercise recovery which was assessed by examining heart rate variability (HRV), for the knee extensor muscle group in young healthy adults.

Methods

For this study, 105 men between 18 and 30 years of age were randomized into 4 groups: concentric control (CONCC), eccentric control (ECCC), concentric training (CONCT) and eccentric training (ECCT). The CONCC and ECCC groups underwent one session of resistance exercise (RE) using the knee extensor muscle group (3 sets of 1 repetition at 100% of the maximal repetition [1MR]) and the CONCT and ECCT groups performed 10 training sessions. The HRV was analyzed at baseline and across four recovery periods (T1, T2, T3 and T4).

Results

The ECCT group exhibited increased muscle strength at the end of the study. Regarding cardiac autonomic modulation, the CONCC and ECCC groups exhibited increases in overall variability (SDNN and SD2) at T1 compared to baseline, and the ECCT group demonstrated increases in variables reflecting vagal modulation and the recovery process (RMSSD, SD1 and HF [ms²]) at T1, T2 and T4 compared to baseline.

Conclusions

Resistance training with emphasis on eccentric contractions promoted strength gain and an increase in cardiac vagal modulation during recovery compared to baseline.     

Pain intensity and cervical range of motion in women with myofascial pain treated with acupuncture and electroacupuncture: a double-blinded,randomized clinical trial

BACKGROUND:

Acupuncture stimulates points on the body, influencing the perception of myofascial pain or altering physiologic functions.

OBJECTIVE:

The aim was to evaluate the effect of electroacupuncture (EAC) and acupuncture (AC) for myofascial pain of the upper trapezius and cervical range of motion, using SHAM acupuncture as control.

METHOD:

Sixty women presenting at least one trigger point at the upper trapezius and local or referred pain for more than six months were randomized into EAC, AC, and SHAM groups. Eight sessions were scheduled and a follow-up was conducted after 28 days. The Visual Analog Scale assessed the intensity of local and general pain. A fleximeter assessed cervical movements. Data were analyzed using paired t or Wilcoxon''s tests, ANOVA or Friedman or Kruskal-Wallis tests and Pearson''s correlation (α=0.05).

RESULTS:

There was reduction in general pain in the EAC and AC groups after eight sessions (P<0.001). A significant decrease in pain intensity occurred for the right trapezius in all groups and for the left trapezius in the EAC and AC groups. Intergroup comparisons showed improvement in general pain in the EAC and AC groups and in local pain intensity in the EAC group (P<0.05), which showed an increase in left rotation (P=0.049). The AC group showed increases in inclination (P=0.005) sustained until follow-up and rotation to the right (P=0.032).

CONCLUSION

: EAC and AC were effective in reducing the pain intensity compared with SHAM. EAC was better than AC for local pain relief. These treatments can assist in increasing cervical range of motion, albeit subtly.     

Balance and muscle power of children with Charcot-Marie-Tooth

BACKGROUND:

In certain diseases, functional constraints establish a greater relationship with muscle power than muscle strength. However, in hereditary peripheral polyneuropathies, no such relationship was found in the literature.

OBJECTIVE:

In children with Charcot-Marie-Tooth (CMT), to identify the impact of muscle strength and range of movement on the static/dynamic balance and standing long jump based on quantitative and functional variables.

METHOD:

The study analyzed 19 participants aged between 6 and 16 years, of both genders and with clinical diagnoses of CMT of different subtypes. Anthropometric data, muscle strength of the lower limbs (hand-held dynamometer), ankle and knee range of movement, balance (Pediatric Balance Scale) and standing long jump distance were obtained by standardized procedures. For the statistical analysis, Pearson and Spearman correlation coefficients were used.

RESULTS:

There was a strong positive correlation between balance and the muscle strength of the right plantar flexors (r=0.61) and dorsiflexors (r=0.59) and a moderate correlation between balance and the muscle strength of inversion (r=0.41) and eversion of the right foot (r=0.44). For the long jump and range of movement, there was a weak positive correlation with right and left plantar flexion (r=0.20 and r=0.12, respectively) and left popliteal angle (r=0.25), and a poor negative correlation with left dorsiflexion (r=-0.15).

CONCLUSIONS:

The data on the patients analyzed suggests that the maintenance of distal muscle strength favors performance during balance tasks, while limitations in the range of movement of the legs seem not to be enough to influence the performance of the horizontal long jump.     

Strength and size ratios between reciprocal muscle groups in the thigh and lower leg of male collegiate soccer players

This study investigated the strength and size ratios between reciprocal muscle groups in the thigh and lower leg of soccer players. In 11 male collegiate soccer players and 21 male non‐soccer players, the joint torques developed during isometric maximal voluntary contractions of the knee extensors (TQ_KE) and flexors (TQ_KF), plantar flexors (TQ_PF) and dorsiflexors (TQ_DF) were determined using a dynamometer. The muscle volumes of the same muscles (i.e. MV_KE, MV_KF, MV_PF and MV_DF) were determined by magnetic resonance imaging. There were no significant differences in any of the joint torques or muscle volumes between soccer and non‐soccer players. TQ_KE/TQ_KF was significantly lower for soccer players than for non‐soccer players. On the other hand, no significant difference in TQ_PF/TQ_DF was found between soccer and non‐soccer players. MV_KE/MV_KF and MV_PF/MV_DF for soccer players were not significantly different from those for non‐soccer players. Additionally, there were no significant correlations between MV_KE/MV_KF and TQ_KE/TQ_KF and between MV_PF/MV_DF and TQ_PF/TQ_DF of soccer players. Thus, the strength ratios appear not to be affected by the size ratios between the knee extensors and flexors and between the plantar flexors and dorsiflexors in soccer players.     

Effectiveness of muscle strengthening and description of protocols for preventing falls in the elderly: a systematic review

Background

Falls are a geriatric syndrome that is considered a significant public health problem in terms of morbidity and mortality because they lead to a decline in functional capacity and an impaired quality of life in the elderly. Lower limb muscle strengthening seems to be an effective intervention for preventing falls; however, there is no consensus regarding the best method for increasing lower limb muscle strength.

Objectives

To analyze the effectiveness of lower limb muscle strengthening and to investigate and describe the protocols used for preventing falls in elderly subjects.

Method

We performed a systematic review of randomized and controlled clinical trials published between 2002 and 2012 in the databases PubMed, EMBASE, Scopus, Web of Science, and PEDro that cited some type of lower limb muscle strengthening protocol and that evaluated the incidence of falls as the primary outcome exclusively in elderly subjects. Twelve studies met the inclusion criteria. Qualitative analysis was performed by independent reviewers applying the PEDro scale.

Results

The data obtained from the selected studies showed lower fall rates in the intervention groups compared to controls. Six studies described the lower limb muscle strengthening protocol in detail. High methodological quality was found in 6 studies (PEDro score ≥7/10 points).

Conclusions

The methodological quality of the studies in this area appears to leave little doubt regarding the effectiveness of lower limb strengthening exercises for preventing falls in elderly subjects, however the interventions in these studies were poorly reported.     

Effect of low-level laser therapy (808 nm) on skeletal muscle after endurance exercise training in rats

BACKGROUND:

Low-level laser therapy (LLLT) has been demonstrated to be effective in optimizing skeletal muscle performance in animal experiments and in clinical trials. However, little is known about the effects of LLLT on muscle recovery after endurance training.

OBJECTIVE:

This study evaluates the effects of low-level laser therapy (LLLT) applied after an endurance training protocol on biochemical markers and morphology of skeletal muscle in rats.

METHOD:

Wistar rats were divided into control group (CG), trained group (TG), and trained and laser irradiated group (TLG). The endurance training was performed on a treadmill, 1 h/day, 5 days/wk, for 8 wk at 60% of the maximal speed reached during the maximal effort test (Tmax) and laser irradiation was applied after training.

RESULTS:

Both trained groups showed significant increase in speed compared to the CG. The TLG demonstrated a significantly reduced lactate level, increased tibialis anterior (TA) fiber cross-section area, and decreased TA fiber density. Myogenin expression was higher in soleus and TA muscles in both trained groups. In addition, LLLT produced myogenin downregulation in the TA muscle of trained animals.

CONCLUSION:

These results suggest that LLLT could be an effective therapeutic approach for stimulating recovery during an endurance exercise protocol.