Exercise as it relates to Disease/The Role of Muscular Endurance Strength Training Post Stroke

This is an analysis of the journal article “Strength Training for Skeletal Muscle Endurance after Stroke” by Ivey et al., (2017)

What is the background to this research?
The research by Ivey and colleagues in 2017 compared two different participant groups who either commenced strength training or stretch control group at least 6 months post stroke. Stroke is defined as a sudden and focal neurological syndrome caused by either an occlusion to blood supply in an area of the brain or an increase of bleeding into brain tissue. The goal of the research was to identify whether specific endurance strength training can improve practical community tasks post stroke. Practical task include mobility in the community with or without gait aid, transfers from different seating positions and vehicles, and the ability to Independently complete all activities of daily living (ADL’s).

Where is the research from?
The participants in the research were recruited from the University of Maryland Medical System or the Baltimore VA Medical Centre referral networks. The authors of this study have also completed research into the effects of resistance training on inflammatory and vascular markers in chronic stroke patients. The authors are highly regarded with research specific to metabolic, cardiovascular, skeletal muscle and functional adaptations within neurological impaired populations.

What kind of research was this?
The research completed was a double blind random control trial (RCT) with a one-experiment group and one control group. The research initially started as a double blind trial however some assessors were involved in the final n=4 participants randomisation. RCT’s are assigned as the highest level of evidence. However the allocation process in this paper resulting in not blinding all assessors shows that it is important to still scrutinise the details of RCT's. The trial includes 30 participants who were randomly assigned into their group by a computer based random number generator.

What did the research involve?
The research involved a strength-training group and a control group based on stretching. Each member of both groups met the inclusion criteria of >6months post stroke with chronic hemiparesis and with the ability to mobilise with or without a gait aid. Outcome measure completed prior to the rehabilitation protocol included unilateral leg press at 70% 1-RM at a cadence of 60bpm to measure skeletal muscle endurance (SME), 1-RM absolute strength test, 6 –minute walk test (6MWT), Peak Oxygen Consumption (VO2 Peak), and a 10 metre walk test (10MWT). No statistically significant differences were found in the outcome measures between the two groups of participants.

The following intervention protocols were completed over a 3-month period:

Limitations of this study include the small sample size of 30 participants. In some instances not all assessors were blinded during the randomisation process resulting in the possibility of biased results. Future research should compare neurological strength training, power training and muscle endurance training to identify the most beneficial strength training protocols for stroke survivors.

What were the basic results?
Strength training participants (n=14) had significantly better Skeletal muscle endurance gains compared with the stretching control group (n=15).

SME Leg Press Test: The strength group were able to complete 178% increase in resistance on paretic side and 161% with non-paretic leg. Compared with an increase of 12% resistance in the stretching control group.

6MWT: Improved completion time and significant intergroup improvement only found in the ST group (P =. 018).

10MWT: No change within either group was observed.

Peak Vo2: 6% increase in the ST group and a 2% decrease in the SC group was observed. 1-RM Strength Test: Significant improvements found in the ST group with 43% increase in paretic leg and 21% in non-paretic leg. Only a 3% increase was found in both paretic and non-paretic legs of the SC group. The ST group had 8 participants drop out between baseline tests and follow up test. Results may therefore be overstated due to the participants from the ST group who did not complete the entire protocol. No dropouts occurred in the SC group. The dropouts occurred due to medical reasons and were not related to compliance and study reasons. No adverse events occurred in either group of participants.

What conclusions can we take from this research?
Strength plays a significant role in the reduced functional capacity in chronic stroke patients. Therefore strength plays a pivotal role in the rehabilitation process for stroke survivors. The paper concludes that resistance training improved sustained submaximal muscle contractions. The improvements found are likely the result of utilising neurological pathways to increase the number of functional motor units in the skeletal muscle. Stroke survivors in previous research demonstrated a decrease in up to 50% functional motor units. Evidence in Multiple sclerosis (MS) in which is a similar neurological disorder to stroke identifies the decrease ability to sustain muscle contractions and force over prolonged periods of time. The research completed in the MS population may help explain why muscular endurance strength training is beneficial in the stroke participants in this study.

Practical advice
The findings from the paper identify the role in which endurance specific resistance training can have during chronic stroke rehabilitation. The role of strength training in the stoke population is backed by reliable and valid research. Previous systematic review undertaken revealed that strength training in stroke survivors increases strength in the specific muscles trained and improved overall function. Therefore it is important to train the specific muscles required for the goal task when completing any form of strength training with individuals post stroke.

Further information/resources
Overview of Stroke

Physical Fitness Training for Stroke Patients

ACSM Guide for Types of Resistance Training

Clinical Guidelines for Stroke Management 2017