We examined the effects of attentional focus instructions on the learning of movement form and carry distance in low-skilled golfers. The X-factor describes the rotation of the shoulders relative to the pelvis, and its increase during the downswing (so-called X-factor stretch) is associated with the carry distance of the ball. X-factor stretch and carry distance have been shown to be associated with an early weight shift toward the front leg during the downswing. In our study, one group (internal focus, IF) was instructed to focus on shifting their weight to their left foot while hitting the ball, whereas another group (external focus, EF) was instructed to focus on pushing against the left side of the ground. A control (C) group was not given attentional focus instructions. Participants performed 100 practice trials. Learning was assessed after a 3-day interval in a retention test without focus instructions. The EF group demonstrated a greater carry distance, X-factor stretch, and higher maximum angular velocities of the pelvis, shoulder, and wrist than both the IF and C groups, which showed very similar performances. These findings demonstrate that both movement outcome and form can be enhanced in complex skill learning by providing the learner with an appropriate external focus instruction. Moreover, they show that a single external focus cue can be sufficient to elicit an effective whole-body coordination pattern.
Jongseong An, Gabriele Wulf and Seonjin Kim
Birgit Larsen, Michael Voigt and Michael J. Grey
The influence of pedaling frequency and crank load on the sensitivity of the soleus short latency stretch reflex (SLR) was examined in nine healthy subjects during pedaling by the use of a custom-built robotic actuator. The SLR decreased successively in downstroke when pedaling frequency increased from 20 to 40 and 60 revolutions per minute at a constant crank load (p = .005). The SLR was unchanged at crank load increases of 2.6 or 5.1 Nm at a constant pedaling frequency (p > .05). Accordingly, it was shown that increased muscle activation level as a consequence of added crank load and increased movement speed does not increase the sensitivity of the soleus SLR.
Koya Mine, Takashi Nakayama, Steve Milanese and Karen Grimmer
Posterior shoulder tightness (PST) and glenohumeral internal-rotation deficit (GIRD) can contribute to shoulder pain suffered by athletes engaged in overhead sporting activities. Stretching is a common intervention to resolve PST and GIRD, but it has weak evidence of effectiveness to date.
This systematic review aimed to collect and synthesize effectiveness data from English- and Japanese-language randomized controlled trials (RCTs) investigating stretching interventions for PST and GIRD.
7 English databases and 3 Japanese databases were searched from inception until December 5, 2015. Only English- and Japanese-language RCTs were considered. Risk of bias in the included studies was assessed using the Physiotherapy Evidence Database scale. Data were synthesized qualitatively.
Eight English-language and 2 Japanese-language papers of low to high quality were included. There was moderate evidence for positive immediate and short-term effects of cross-body stretch on PST and GIRD in asymptomatic young subjects. Moderate evidence was found to suggest that active sleeper stretch might not be more effective than no intervention to improve PST and GIRD in the short term.
Cross-body stretch can be effective to improve PST and GIRD in asymptomatic young subjects immediately or in the short term. Further study with methodological rigor is necessary to investigate the long-term effectiveness of stretching interventions on PST and GIRD in symptomatic patients.
Jailton Thulher do Rosario, Natalia Santos da Fonseca Martins, Carolina Carneiro Peixinho and Liliam Fernandes Oliveira
This study aimed to determine the effects of a functional training and ankle stretching program in triceps surae torque, passive stiffness index, and in the risk for fall indicators in older adults. Twenty women (73.4 ± 7.3 years) were allocated into an intervention or control group. The 12-week intervention consisted of functional training and calf stretching exercises performed twice a week. Measurements of peak passive and active torque, passive stiffness, maximum dorsiflexion angle, and indexes of risk for falls (Timed Up and Go, functional reach test, QuickScreen-test) were collected. There were no significant differences for all variables, except the maximum dorsiflexion angle, which increased in the intervention group from 33.78 ± 8.57° to 38.89 ± 7.52°. The exercise program was not sufficient to enhance performance on functional tests and decrease the risk for falls in older adults. The significant increase in the maximum dorsiflexion indicates a positive impact of stretching exercises.
Jacinto Javier Martínez-Payá, José Ríos-Díaz, María Elena del Baño-Aledo, David García-Martínez, Ana de Groot-Ferrando and Javier Meroño-Gallut
The objective of this observational cross-sectional study was to investigate the normal motion of the median nerve when stretched during a neurodynamic exercise. In recent years, ultrasonography has been increasingly accepted as an imaging technique for examining peripheral nerves in vivo, offering a reliable and noninvasive method for a precise evaluation of nerve movement. Transverse motion of the median nerve in the arm during a neurodynamic test was measured. A volunteer sample of 22 healthy subjects (11 women) participated in the study. Nerve displacement and deformation were assessed by dynamic ultrasonography. Excellent interobserver agreement was obtained, with kappa coefficient of .7–.8. Ultrasonography showed no lateral motion during wrist extension in 68% of nerves, while 73% moved dorsally, with statistically significant differences between sexes (ORlat = 6.3; 95% CI = 1.4–27.7 and ORdor = 8.3; 95% CI = 1.6–44.6). The cross-sectional area was significantly greater in men (3.6 mm2). Quantitative analysis revealed no other statistically significant differences. Our results provide evidence of substantial individual differences in median nerve transverse displacement in response to a neurodynamic exercise.
Bruce C. Elliott, Kevin G. Baxter and Thor F. Besier
This research examined the influence on performance of no-pause and mean delays of 0.97 s and 1.5 s between the eccentric and concentric phases of the stretch-shorten cycle movement of internal rotation (IR) of me upper arm. Videography and surface electromyography were used in the assessment of 19 athletes throwing a baseball in a manner that constrained all degrees of freedom other than upper-arm IR. Results demonstrated that the pectoralis major, latissimus dorsi, and anterior deltoid muscles were all active at above 100% maximum voluntary contraction (MVC) during IR. The maximum velocity of the wrist decreased with increasing pause time between me eccentric and concentric phases of the IR movement. A mean 21.9% augmentation to the maximum wrist velocity was recorded when the no-pause delay and a mean delay of 1.5 s were compared. There were no electromyographically discernible differences recorded either prior to or after release for any of the monitored muscles during IR across the pause conditions. It is evident therefore that the benefits of a prestretch during external rotation (ER) have a significant influence on the subsequent velocity of IR.
Mark Kluemper, Tim Uhl and Heath Hazelrigg
Imbalanced shoulder muscles might cause poor posture in swimmers, which has been implicated as potential cause of injury.
To determine whether a training program can reduce forward shoulder posture.
College swimming pool.
39 competitive swimmers (age 16 ± 2 years) divided into an exercise group (n = 24) and a control group (n = 15).
The experimental group performed a partner-stretching program on the anterior shoulder muscles and a strengthening regimen focusing on the posterior shoulder muscles for 6 weeks. The control group participated in normal swim-training activities.
Main Outcome Measures:
Shoulder posture was measured as the distance from the anterior acromion to a wall using a double-square method.
The experimental group significantly reduced the distance of the acromion from the wall in a resting posture (–9.6 ± 7.3 mm) as compared with the control group (–2.0 ± 6.9 mm).
A training routine might reduce the forward shoulder posture present in most competitive swimmers.
Phillip A. Gribble, Kevin M. Guskiewicz, William E. Prentice and Edgar W. Shields
The purposes of this study were to determine the effects of static and hold-relax stretching on hamstring range of motion and to examine the reliability of the FlexAbility LE1000 compared with the goniometrically measured active knee-extension test. Forty-two participants (18–25 years old) were assigned to either a control, static, or hold-relax training group. Participants were stretched four times a week over a 6-week period, with four 30-s stretches per session using a straight-leg-raise method on the FlexAbility LE1000. It was determined that both static and hold-relax techniques significantly improved hamstring flexibility (ISLR: +33.08° ± 9.08° and +35.17° ± 10.39°, respectively). Participants of both techniques reached a plateau in flexibility improvement between Weeks 4 and 5. Thus, static and hold-relax stretching are equally effective in improving hamstring ROM. The FlexAbility LE1000 and the goniometer were both found to be highly reliable. Therefore, either measurement technique could be used successfully to measure hip-flexion ROM.
Marie A. Johanson, Brian J. Cuda, Jonathan E. Koontz, Julia C. Stell and Thomas A. Abelew
Stretching exercises are commonly prescribed for patients and healthy individuals with limited extensibility of the gastrocnemius muscle.
To determine effects of gastrocnemius stretching on ankle dorsiflexion, knee extension, and gastrocnemius muscle activity during gait.
Sixteen volunteers (9 men and 7 women, mean age = 27 y) with less than 5° of passive ankle-dorsiflexion range of motion randomly assigned to an experimental or control group.
The experimental group performed gastrocnemius stretching for 3 wk.
Main Outcome Measures:
Maximum ankle dorsiflexion, maximum knee extension, and EMG amplitude of the gastrocnemius muscles were measured between heel strike and heel-off before and after intervention.
No significant effect of group or time was found on maximum ankle dorsiflexion, maximum knee extension, or EMG activity of the medial or lateral gastrocnemius muscles between heel strike and heel-off. The experimental group had significantly greater passive ankle-dorsiflexion range of motion bilaterally at posttest than the control group.
Stretching did not alter joint angles or gastrocnemius muscle activity in the early to midstance phase of gait.
James R. Debenham, William I. Gibson, Mervyn J. Travers, Amity C. Campbell and Garry T. Allison
Eccentric exercises are increasingly being used to treat lower-limb musculoskeletal conditions such as Achilles tendinopathy. Despite widespread clinical application and documented efficacy, mechanisms underpinning clinical benefit remain unclear. Positive adaptations in motor performance are a potential mechanism.
To investigate how an eccentric loading intervention influences measures of stretch-shortening-cycle (SSC) behavior during a hopping task.
Within-subjects repeated-measures observational study.
University motion-analysis laboratory.
A single intervention of 5 sets of 10 eccentric plantar-flexion contractions at 6 repetitions maximum using a commercial seated calf-raise machine.
Main Outcome Measures:
Lower-limb stiffness, sagittal-plane ankle kinematics, and temporal muscle activity of the agonist (soleus) and antagonist (tibialis anterior) muscles, measured during submaximal hopping on a custom-built sledge-jump system.
Eccentric loading altered ankle kinematics during submaximal hopping; peak angle shifted to a less dorsiflexed position by 2.9° and ankle angle precontact shifted by 4.4° (P < .001). Lower-limb stiffness increased from 5.9 to 6.8 N/m (P < .001), while surface EMG measures of soleus occurred 14–44% earlier (P < .001) after the loading intervention.
These findings suggest that eccentric loading alters SSC behavior in a manner reflective of improved motor performance. Decreased ankle excursion, increased lower-limb stiffness, and alterations in motor control may represent a positive adaptive response to eccentric loading. These findings support the theory that mechanisms underpinning eccentric loading for tendinopathy may in part be due to improved “buffering” of the tendon by the neuromuscular system.