Article critique
1. What study report is this?
Hayes, B. T., Harter, R. A., Widrick, J. J., Williams, D. P., Hoffman, M. A., & Hicks-Little, C. A. (2012). Lack of neuromuscular origins of adaptation after a long-term stretching program. Journal of Sports Rehabilitation, 21, 99-106.
2. Purpose and general rationale. What was the general purpose of the study? What questions does it raise?
The purpose of this study was to examine the possible neurological origin and adaptations in the Ia-reflex pathway that allows the increase the flexibility of ankle range of motion (ROM). This study evaluated the neurological changes occurring with increase in flexibility in the soleus during 6-week static stretching program. It raises the question that whether the reduction in the synaptic transmission of Ia afferents to the motor neuron pool is responsible for increase in the flexibility in ankle ROM.
3. Fit and specific rationale. How does answering the research question(s) add something new to what is already known? If the study is a replication, why is that important?
The study is an experimental research to understand the physiological adaptations occurring in the neuromuscular system as a result of long-term static stretching. In contrast to the current literature, no significant neurological changes were observed after six weeks of static stretching. This study adds that the neuromuscular origins of adaptation do not exist in Ia-reflex pathway and the increase in the flexibility in ankle ROM may be because of mechanical changes or stretch tolerance.
4. Participants. Who or what was studied? (Number and key characteristics)
Forty healthy subjects including 20 women and 20 men (22.37 ± 3.13 years, 174.28 ± 9.29 cm, 77.72 ± 17.71 kg), with no history of cognitive & neurological impairment and lower extremity surgery or injury within previous one year
5. Context. Where did the study take place?
Not mentioned in the article
6. Steps in sequence. In sequential order, what were the major steps in performing the study? (Record these in a flowchart-use additional sheet only if needed.) Do not just repeat details from Items 1-5 and 7-10. Create an explanatory sketch that a year from now would help you recall how the study was done.
Forty healthy subjects without any history of cognitive & neurological impairment and lower extremity surgery or injury were chosen
Subjects were divided into experimental and control groups
Subjects were prepared for surface electromyography (EMG) to measure H-relfex and M-wave
EMG measurements were done in a specific prone position of the subjects
Ankle dorsiflexion PROM was evaluated by blind-folding the subjects in a semi-reclined position
Stretching protocols were given to the different groups of the subject
Experimental groups performed three different stretches, five times for thirty seconds
They stretched for five times per week over a six-week period
The control group did not stretch
Subjects recorded a journal (with date and time) of each stretching session
Results of the study were statistically analyzed using repeated-measures MANOVA factorial design
7. Data.
Neuromuscular and flexibility testing after three and six weeks (testing of ankle dorsiflexion through PROM, Hmax: M max, level of presynaptic inhibition and disynaptic reciprocal inhibition)
8. Analysis. What kind(s) of data analysis was used? (e.g. statistical, logical categorization, etc.)
2 X 3 repeated measures MANOVA factorial design was used for data analysis.
Paired t-tests were used to determine mean differences when the above test yielded a significant F-ratio (for group X time interaction).
Intraclass correlation coefficient (ICC2,1) was used to check intersession reliability over two trials.
All statistical analysis was performed using SPSS software, version 11.5.
9. Results. What were the results?
In the experimental group, the change in ROM was 11.37º whereas in the control group, it was 0.59º. The experimental group had significantly improved PROM from baseline to three weeks and from three weeks to six weeks (mean 11.2°± 0.9°, P < .001). This group had 42.3% increase in ankle-dorsiflexion PROM from baseline to six weeks. No group X time interactions were observed for Hmax:Mmax, presynaptic inhibition, and disynaptic reciprocal inhibition. The intersession reliability (ICC2,1) was measured with the control subjects to assess the stability and consistency of the measurement protocol. All the measured parameters had high consistency (Hmax:Mmax [R = 0.808], ankle-dorsiflexion PROM [R = 0.977], presynaptic inhibition [R =0.810], and disynaptic reciprocal inhibition [R = 0.786]).
10. Conclusions. What does the author conclude?
11. What cautions does the author raise about interpreting the study, and what do you think are important reservations?
The lack of significant motor-neuron excitability changes after six weeks of static stretching and significant increase in the flexibility limited the investigation. The authors were not able to evaluate the influence of pre-synaptic and post-synaptic mechanisms on the inhibition of motor-neuron pool excitability. This study was underpowered to look into the effects of sex distribution in the subjects.
12. What particularly interesting or valuable things did you learn from reading the report?
The conclusion drawn in this study contrasted the current scientific literature. Mechanical/stretch tolerance has higher influence on increase in ankle-dorsiflexion PROM as compared to neuromuscular mechanisms.
