HDE 100C Strength Training Impact On Muscle Cell

STRENGTH TRAINING IMPACT ON MUSCLE CELL STRUCTURE 1

Strength Training Impact on Muscle Cell structure

Vi Tran

Professor Ober

STRENGTH TRAINING IMPACT ON MUSCLE CELL STRUCTURE 2

Strength Training Impact on Muscle Cell Structure

Muscles are soft tissues found in bodies of majority of animals. Their cells are comprised

of filaments, which produce contractions that bring about change in the length and shape of the

cells. These muscles function to produce motion and force. However, there are several types of

muscles whose main role is to maintain and change posture and movement of both internal and

external organs. For these muscles to function well, strength training is recommended to some

extent. Exercise has a lot of impact on muscles their bones, connective tissue and the nerves that

stimulate them. One of these effects is the increase in the size of muscle cells. This is caused by

the formation of myofibrils that increase thickness of fibers which in turn causes the enlargement

of muscles. This is mostly evident in athletes and other body builders. The aim of this paper is to

review analyze several articles that discuss the impact of strength training on muscle cell

structure.

Description of Methods

In the first article, MacDougall et al (2015) did an experimental research whereby six

subjects were put in a controlled environment for observation. The subjects were health young

men who engaged in body building training. After refraining from exercise for about three days,

the subjects performed typical sessions for elbow flexors in the morning. In addition, they were

instructed to consume their normal meals and return to the laboratory in the evening for blood

sampling, which was also done the following morning after 8 hours of sleep. The aim of this

experiment was to measure Muscular Protein Synthesis rate (MPS), which leads to growth of

muscle cells, of the subjects after an intense strength training (MacDougall et al, 2015). The rate

of Muscular Protein Synthesis for each subject was determined from the enrichment of plasma

using a primed constant infusion. MPS was therefore calculated according to Nair’s method and

STRENGTH TRAINING IMPACT ON MUSCLE CELL STRUCTURE 3

expressed as a percentage. Differences in Muscular Protein Synthesis for the six subjects were

assessed using variance analysis.

In the second article by Miller et al (2017), 171 individuals were referred to an

experimental study. Unlike in the first article, these subjects were comprised of both men and

women. Based on the taken blood tests all the subjects had normal blood count, liver, and thyroid

function among other requirements. This study entailed older adults having knee osteoarthritis

(Miller et al, 2017). However, some individuals who had other complications in order to ensure

that they did not influence the responses. In addition, it comprised of a 12 week training

program. Before the commencement of the program, all the subjects underwent a 2 week run to

ensure that they were all eligible for the training so as to reduce subsequent dropouts. The

resistance exercise training was set at an intensity of 60% of 1 Repetition Maximum (RM) so

that the individual will not experience difficulties in completing the training due to pain

limitations (Miller et al, 2017). RM was assessed after every week. Throughout the 12 weeks one

trainer oversaw all the testing and training. As in the first study, changes of muscle strength as

well as physical characteristics were determines through measures of variance analysis. This

model is considered conservative instead of taking average value for each subject. Pearson’s rule

was used to confirm the relationship between variables.

In the third article by Dreyer et al (2016), 11 young individuals participated in a study

approved by Institutional Review Board of the University of Texas Medical Branch. All the

subjects were perfectly healthy and physically active and were not currently involved in any type

of exercise training. Just like in the second article, the participants comprised of both men and

women. Five days before the beginning of the study, the subjects were tested for muscle strength

by measuring their 1 RM. To make sure that the results were reliable, the subjects were fed

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standard meals, studied overnight and refrained from exercise prior to the study (Dreyer et al,

2016). Study design comprised of 3 to 4 hours of exercise as well as 2 to 3 hours basal and two

periods of post exercise. While blood samples were taken to measure glucose uptake and pH,

biopsy samples measured Muscle Protein Synthesis (MPS).

According to Burd et al (2012) eight resistant trained men were recruited to the study.

Subjects were deemed to be healthy based on their responses to a medical questionnaire. In

addition, they had to be habitually active and engaged in exercise training for at least twice a

week in two years prior to the study. The local Research Ethics Board of McMaster University

and Hamilton Health Sciences approved the study as well as conforming it to the standards for

the use of human subjects (Burd et al, 2012). Subjects reported to the lab two week prior to the

training for training where they were refrained from exercise and recorded their diets. During the

training, the participants did leg extensions and other intense exercises. The standard precursor

product equation was utilized to calculate the fractional synthetic rates (FSR) for muscle proteins

(Burd et al, 2012). Linear regression was used to assess any deviation whereas Pearson’s product

correlation determined the relationship between variables. Standard error was used as a mean of

presenting the results.

Results and Author’s Interpretation

According to MacDougall et al (2015), a coefficient of 0.82% was obtained after analysis

of plasma enrichment. They had a remarkable consistency between one and half and ten and half

hours, which represented the greatest percentage of the time over which muscular protein

synthesis was determined. After MPS was determined, results show a different of 14% between

the controlled and exercised arms. In other words, the exercised arm had a higher muscular

protein synthesis. However the observed increased in MPS was accompanied by an increase in

STRENGTH TRAINING IMPACT ON MUSCLE CELL STRUCTURE 5

muscle protein degradation, which according to MacDougall et al (2015) may be as a result of

the mechanical damage that is known to occur during heavy exercises.

Results by Miller et al (2017) show that the training improved the 1 RM in the subjects

under study. In addition, most of the improvements were noted in the whole muscle performance

with moderate resistance exercises. The provoked substantial improvements were equal for both

men and women. There was no significant difference between the results for both, hence Miller

at al interpreted that gender does not have impact in muscular protein synthesis (2017). On

contrary, there were some outcomes which differed in gender. For instance, myosin light chain

fibers were high in men and low in women.

Dreyer at al denote that blood flow and glucose uptake increased during exercises (2016).

However, muscle protein synthesis decreased immediately after exercise with a significant

increase in fractional synthetic rates. According to the authors, the decrease in muscular protein

synthesis was associated with increase in AMPK activity, which inhibits ATP consuming

anabolic processes such as MPS (Dreyer et al, 2016). Nevertheless, this mechanism is yet to be

determined. There are also other factors such as acidosis that are known to inhibit muscle protein

synthesis.

According to Burd et al (2012), muscle protein synthesis is observed to decrease during

the first six hours of exercise. However, there was a detectable increase in the rates of MPS

during 24 to 30 hours following exercise. The report shows that the impact of resistance exercise

on muscular protein synthesis is only partial (Burd et al 2012). The main reason behind this is

that this mechanism is dependent on muscle time under tension hence the longer the time of

exercise the higher the MPS.

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Discussion and conclusion

After analyzing the results from all the articles, implications are that strength training

have a positive impact on muscle cell structure. However, since most of the promising data was

measured after a long period of exercise the assumption was that muscle protein synthesis is liner

across the period of assessment. Most of the findings in these articles are consistent with the

existing literature. The main limitation across the studies in all the articles is that control groups

were not included. In summary, the findings support the hypothesis that strength training

increase muscle size and shape. An interesting question that leaves a gap to be filled by future

studies is why there was a decrease in muscle protein synthesis during the early hours of

exercise. Although there are presumptions, they are yet to be proved true. This means that our

understanding on the influence of strength training on muscle structure is still unclear.

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References

Burd, N. A., Andrews, R. J., West, D. W., Little, J. P., Cochran, A. J., Hector, A. J., ... &

Phillips, S. M. (2012). Muscle time under tension during resistance exercise stimulates

differential muscle protein sub‐fractional synthetic responses in men. The Journal of

physiology, 590(2), 351-362.

Dreyer, H. C., Fujita, S., Cadenas, J. G., Chinkes, D. L., Volpi, E., & Rasmussen, B. B. (2016).

Resistance exercise increases AMPK activity and reduces 4E‐BP1 phosphorylation and

protein synthesis in human skeletal muscle. The Journal of physiology, 576(2), 613-624.

MacDougall, J. D., Gibala, M. J., Tarnopolsky, M. A., MacDonald, J. R., Interisano, S. A., &

Yarasheski, K. E. (2015). The time course for elevated muscle protein synthesis

following heavy resistance exercise. Canadian Journal of applied physiology, 20(4), 480-

486.

Miller, M. S., Callahan, D. M., Tourville, T. W., Slauterbeck, J. R., Kaplan, A., Fiske, B. R., ...

& Toth, M. J. (2017). Moderate-intensity resistance exercise alters skeletal muscle

molecular and cellular structure and function in inactive older adults with knee

osteoarthritis. Journal of Applied Physiology, 122(4), 775-787.

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