Platelet Rich Plasma Therapy — Out of Pocket Cost for Peace of Mind?

/WebMaterial/ShowPic/860386Since its first clinical efficacy introduction in 1987, Platelet Rich Plasma (PRP) therapy has had its share of support and skepticism as a method to promote tissue repair and regeneration. Through centrifugation, the plasma becomes five to ten times more concentrated with platelets, growth hormones, and plasma proteins such as fibrin and fibronectin.  PRP is typically injected into areas of trauma to stimulate the body stages of wound healing. This type of therapy is widely associated with the treatments of musculoskeletal injuries. Additionally, PRP therapy can be used in cardiovascular treatments such as heart surgery and angiogenesis, as well as dermatology treatments such as acne scars, contour defects, androgenic alopecia, wound ulcers and striae distensae. Different types of growth factors in PRP have been categorized into their subgroups and associating functions depending on characteristics of platelet-derived, vascular-endothelial, insulin-like, transforming, hepatocyte, fibroblast and epidermal; however, PRP mechanisms of actions are not completely understood by the scientific community. In other words, there is not enough evidence to completely support the efficacy and uses of PRP for clinical treatments.

/WebMaterial/ShowPic/860388Even in the early introduction of PRP, the serum was utilized in a progressive way through the use of injections directly into the trauma site of a patient.  A study in 1998 called “Platelet Rich Plasma, Growth Factor Enhancement for Bone Grafts”, was intriguing in the amount of efforts taken to observe PRP effects. In this study, a bone graft harvester along  and ElectroMedics 500 gradient density separator is used to extract the platelets from the plasma. One group of the subjects received the cancellous cellular marrow grafts without PRP, while the other group received grafts with PRP added during the bone-milling process and applied topically after replacement of the defect. The bone grafts were allowed to sit and consolidate for 6 months, with panoramic X-ray observation every two months. Looking specifically at the growth factors PDGF and TGF-b (platelet-derived and transforming, respectively), the bone grafts treated with the PRP showed a 338% increase of platelet count. At 2,4 and 6 months respectively, the PRP treated grafts had 2.16, 1.88, and 1.62 times more platelets than the control group, with a p value for each comparison being .001 showing statistical significance. Does this mean that PRP will absolutely enhance growth factors?  Identifying only 2 of the many growth factors is an oversimplification of human physiology. Even though PDGF and TGF-b are not the only ones with properties of angiogenesis, vascularization, mitogenic, and osteogenesis, the insight of this study still illustrates the significant of PRP in recovery.

On the contrary, studies also showing no correlation between PRP and growth factor activation. In a study by Earl G. Freymiller called “Investigation of Platelet-Rich Plasma in Rabbit Cranial Defects: A Pilot Study,” 15 rabbits received 4 equal defects 8 mm in diameter on their cranium.  The sample group was then given grafts of autogenous bone, PRP injection, grafts of autogenous bone with PRP, and no treatment as control. Observation occurred at 1, 2 and 4 month intervals with 5 rabbits per interval. The results show Bone with PRP has higher percentage bone area recovery than Bone group; however, no statistical significant can be observed (p<0.02) radiographically or histomorphometrically.  Does this mean that PRP has no effect on the rat cranium? An important note is the size of this study The sample size and cranium defects were relatively small. Furthermore among the 4 groups, no statistical differences can be observed in bone density at the 4 months interval. This question the precision of measuring technologies and methods. A reasonable conclusion could be PRP does not adversely affect the process of bone recovery or the study is not precise and therefore inconclusive. 

Given some context, these two studies have merit that does not necessarily contradict each others.  Overall, PRP has been shown to be effective in cosmetics and treatment of chronic tendon injuries but lack scientific proofs in treatments of acute ligament, muscle, and fractures injuries.  Though the scientific community has a understanding of PRP components, the lack of understanding in its holistic mechanism of action brings forth doubt in the clinical setting. This controversy remains prevalent because of its clinical and financial constigents.  In the academic community, Healio posted Orthopaedics Today 2018 containing issues of the demands for PRP definition, comprehensive description, healing mechanisms, and functional outcome. To normal society, PRP efficacy recognition is so limited that few to no insurance plans and workers’ compensation would provide even partial reimbursement.  PRP therapy is currently a luxury for the peace of mind, why else would you spend $600 on something that might not work?

Questions to Consider:

Is Platelet Rich Plasma the same as blood doping and to what extent should it be regulated?

If PRP is effective in all form of wound recovery, what proofs are needed before it can be recognized as part of insurance claim?


[1] Alves, Rubina, and Ramon Grimalt. “A Review of Platelet-Rich Plasma: History, Biology, Mechanism of Action, and Classification.” Skin Appendage Disorders, Karger Publishers, 6 July 2017,

[2] Arshdeep, Kumaran M S. Platelet-rich plasma in dermatology: Boon or a bane?. Indian J Dermatol Venereol Leprol 2014;80:5-14

[3] Marx, Robert Lee DDS. Platelet- rich Plasma Growth factor enhancement for bone grafts. Oral and Maxillofacial Surgery 1998

[4] Aghaloo, Tara L DDS. Investigation of platelet-rich plasma in rabbit cranial defects: A pilot study. Journal of Oral and Maxillofacial Surgery 2002

How It Works: NIRS for Determining Oxygen Use


By: Elspeth Grasso, Dan Owens and Laura Sturgill

Recommended Further Reading:

Recent developments in near-infrared spectroscopy (NIRS) for the assessment of local skeletal muscle microvascular function and capacity to utilize oxygen

Near-infrared spectroscopy-derived tissue oxygen saturation in battlefield injuries: a case series report

Moxy device guidebook

Indocyanine green kinetics with near-infrared spectroscopy predicts cerebral hyper fusion syndrome after carotid artery stenting

The Use of Portable NIRS to Measure Muscle Oxygenation and Haemodynamics During a Repeated Sprint Running Test

Muscle Fiber Composition In Competitive Powerlifters

Yesterday, I came across a paper focusing specifically on power lifters and how their muscle fiber compositions compare to sedentary counterparts. The study took vastus lateralis biopsy samples from 5 competitive power lifters, and 5 sedentary participants. Muscle fiber compositions were determined using MTPase histochemical analysis. Interestingly, it was found that sedentary participants expressed 12% type 2B fibers, while power lifters expressed an 11-percent decrease to 1% type 2B. Conversely, power lifters expressed 45% type 2A fibers compared to the sedentary group’s 33%.

Recently in class, I had the opportunity to present on another paper that studied the correlation between muscle fiber composition and obesity. The results found that there was a positive correlation between muscle type 2B fibers and BMI. Obese patients expressed 18% type 2B fibers, significantly more than their lean counterparts. The apparent increase in fiber type 2B expression in obese people compared to an apparent decrease in expression of type 2B in power lifters engenders questions as to the reasons behind the shifts.

This seems to communicate that the training, genetic make-up, or both of the competitive power lifters population appears to encourage more type 2A fast-twitch fibers compared to type 2B. The study was limited to groups of n=5, and would likely be greatly informed with an increased sample size. Additionally, a longitudinal study following the muscle fiber composition of individuals proceeding from novice to competitive power lifting could help isolate the effects of training of relative fiber type2A/B compositions.



References for further reading:

  1. Fry, A. C. et al. Muscle fiber characteristics of competitive power lifters. J. Strength Cond. Res. 17, 402–410 (2003).
  2. Tanner, C. J. et al. Muscle fiber type is associated with obesity and weight loss. Am. J. Physiol. Metab. 282, E1191–E1196 (2002).


Epigenetic Muscle Memory

What comes to mind when I hear the term muscle memory is the typical example being able to ride a bike with ease even if you haven’t ridden one in a long time.  This time of memory is neurologic and comes from repetition of motor tasks. It primarily involves the dorsolateral premotor cortex and cerebellum.[1] However, there is a different kind of muscle memory that a recent study just discovered a lot about.[2] This muscle memory is referring to epigenetic changes to the DNA of human skeletal muscle.

Epigenetics is changes that affect gene expression without altering the DNA sequence but instead turn on and off specific genes. Three ways that genes can be silenced are DNA methylation, histone modifications, and RNA-associated silencing.[3] DNA methylation is what plays a key role in muscle memory and is a major part of the study.  It is a chemical process of adding a methyl group onto DNA that only occurs where cytosine and guanine nucleotides are next to each other and the guanine is linked to a phosphate.[2] This is referred to as a CpG site.

This study used 8 healthy males with no previous training. They went through three phases: loading, unloading, and reloading. Whole-body DEXA and vastus lateralis muscle biopsies were taken at baseline and at the end of each phase. Over 850,000 CpG sites were investigated. Many genes where found to be hypomethylated and showed increased gene expression. This epigenetic memory of earlier muscle growth means that at a later time there can be a greater response to exercise and more muscle growth.


As a person who has encountered many injuries and been forced to take multiple weeks off from the gym, it is comforting to know that despite the loss in strength that occurs during the time off my muscles will hold this memory and be more capable of regaining it.

One possible major implication of this study is a change in bans due to performance enhancing supplements, as this could mean the effects may be much longer lasting. Should people caught using them ever get to return to their sport knowing this? More research needs to be done on this specifically before real decisions can be made on this but it is definitely a future path for this research


References and further readings

[1] Robb T. How to play like a pro: The neuroscience of muscle memory. Oxford Neurological Society. Published 2016. Accessed March 14, 2018.

[2] Seaborne RA, Strauss J, Cocks M, et al. Human Skeletal Muscle Possesses an Epigenetic Memory of Hypertrophy. Sci Rep. 2018;8(1):1898. doi:10.1038/s41598-018-20287-3.

[3] Simmons, D. (2008) Epigenetic influence and disease. Nature Education 1(1):6

[4] Improving your Muscle Memory – Making Good Technique Automatic. National Federation of State High School Associations. Published 2014. Accessed March 14, 2018.

[5] Sharples AP, Stewart CE, Seaborne RA. Does skeletal muscle have an “epi”-memory? The role of epigenetics in nutritional programming, metabolic disease, aging and exercise. Aging Cell. 2016;15(4):603-616. doi:10.1111/acel.12486.

No Pain, No Gain: Stop taking those NSAIDs!

Most athletes have heard the term, “no pain, no gain” at one point or another in their athletic careers, but this saying is truer than one might think. Having grown up in a household where sports were played year round, it was common to take over the counter non-steroidal anti-inflammatory drugs (OTC NSAIDs), such as ibuprofen or aspirin to ease the pain. Ran too far? Easy solution, take some Advil. Overdo it with the lifting? Take a few Motrin and you’ll be ready in the morning. It was even common to take these over the counter drugs before a workout, as a way to get a head start on the pain.

Ibuprofen, a common OTC NSAID.

Is there any validity to this solution? OTC NSAID’s are known for their ability to reduce fevers and minor aches and pains. With that being said, are they really useful for exercise related injuries or pains? Specifically, are they safe and effective to use for delayed onset muscle soreness (DOMS) due to exercise?

DOMS is the pain and stiffness that is felt typically between 24 and 72 hours after the workout has been completed but can last up to 7 days. After a strenuous workout, the body responds with acute inflammation as a natural way to heal the body. This inflammation usually goes hand in hand with DOMS, but the specifics of this relationship have not been clearly defined. Many athletes try to combat this by taking ibuprofen (or other OTC NSAIDs) to ease the pain, but recent studies have shown that this isn’t necessarily a foolproof plan.

In a 2006 study completed by Nieman et al., the influence of ibuprofen was measured during the 160-km Western States Endurance Run on endotoxemia (the presence of endotoxins in the blood), inflammation and plasma cytokines. The study included 29 ultramarathoners who consumed 600 and 1200mg ibuprofen the day before and on the race day, respectively, and 25 controls that competed in the race but did not take ibuprofen or any other medications. Blood and urine samples were collected the morning prior to and immediately following the race, and subjects recorded muscle soreness during the week following the race using a 10-point Likert scale. It was found that ibuprofen use compared to non-users did not alter muscle soreness or damage. In addition ibuprofen use was linked to elevated indicators of endotoxemia and inflammation. One limitation of the study was that it did not have a placebo group due to ethical concerns from the race director, but they may have had an impact on the results. In addition, race conditions are not the best conditions to conduct an experiment under, as they can cause extra stress on the body, affecting the results.

In another study conducted by Donnelly et al., 32 volunteers participated in a study in which ibuprofen was tested against an identical placebo for its effectiveness in reducing muscle soreness and damage after two periods of downhill running. Volunteers took two 600mg ibuprofen or placebo tablets 30 minutes before each run, and took one 600mg tablet every six hours up to 72 hours post-exercise. Blood samples were drawn pre- and post-exercise, and at 6, 24, 48 and 72 hours and analyzed for indicators of muscle damage and inflammation. A questionnaire was used to determine muscle soreness for different regions of the body (the results can be seen in Table 1). The results indicated that ibuprofen is not an appropriate treatment for DOMS and muscle damage. However, one limitation of this study was that during the 10 week break between the two periods of running, there was no monitoring or control of the participants, which means their lifestyles could have been very different from each other, thereby affecting the results.

Furthermore, it is known that exhaustive physical activity leads to small intestinal injury and short-term loss of gut barrier function in otherwise healthy individuals. Another study, conducted in 2012 reveals that ibuprofen aggravates this exercise-induced small intestinal injury and induces gut barrier dysfunction in healthy individuals.

Based on this research, I have concluded that OTC NSAIDs should be discouraged as a way to mitigate the pain that comes with delayed onset muscle soreness. The data from the first two studies show that ibuprofen (and implied other NSAIDs) are not a satisfactory way to decrease the pain that comes from delayed onset muscle soreness. The third study shows that ibuprofen can be extremely harmful to the user and therefore should not be taken if it can be avoided. Based on this information, not only should OTC NSAIDs not be taken for DOMS, but the relationship between inflammation and DOMS should be more thoroughly investigated. It could be that the inflammation isn’t causing DOMS and that is why the drugs aren’t relieving the pain. However, the first study suggests that the intake of ibuprofen increased inflammation, the exact opposite of what it was supposed to do. Either way, ibuprofen and other NSAIDs should not be taken for relief from DOMS.

Questions to consider:

Do you take OTC NSAIDs such as ibuprofen or Advil when you are feeling sore after a hard workout? Do they help? Will you continue?

How often do you think people who exercise regularly take OTC NSAIDs? Should this change?

What may be an alternative to taking NSAIDs for muscle soreness?

Do you still think it is safe to take NSAIDs for other types of pain, such as menstrual cramps, headaches or fevers?

Further Reading:

An article looking at the prevalence of using analgesics (includes NSAIDs) in exercise – related pain

An article looking at the effect ibuprofen has on neutrophils (white blood cells that are an important part of the inflammatory response)

Last year’s blog post discussing at delayed recovery after exercise due to NSAIDs 


Calories Counted on Exercise Equipment

By: Allison Naumann, Claire Paddock, and Christian Poindexter

Recommended Further Reading:

What is a Calorie?

Exercise Machines Lie About Burned Calories – Institute for Natural Healing

Burning Calories with Exercise – Hospital for Special Surgery

MET Values Table – National Cancer Institute

How to Calculate How Many Calories You Burn – Very Well Fit

JSS, et al. “Prediction of Energy Expenditure from Heart Rate Monitoring during Submaximal Exercise.” Journal of Sports Sciences, vol. 23, no. 3, 2005, pp. 289–297.


HIIT: Is it all it’s hyped up to be?

By Andrew Taylor and Kathleen Wright

 Figure 1.  Women participate in a HIIT class.

How many of us have said we would go to the gym, only to realize later that we don’t have the time? High-intensity interval training (HIIT) classes have increased in popularity over the last few years, partly because the sessions are shorter than traditional workouts. HIIT workouts alternate short (20 or 30 second) intervals of maximum exertion with periods of rest or low-intensity exercises. Elite athletes might take part in HIIT to improve their aerobic energy metabolism and performance. If you have ever played a demanding sport, you have probably been subjected to HIIT during the game or practice. The recent obsession with HIIT raises the question: is it just a fad, or will it stick around as an effective means of exercise?

HIIT can be defined as brief exercise that generates a VO2peak, or 90% of the maximum VO2 potential, commonly followed by a relaxation period. This study utilized the Wingate test: participants repeated 30 seconds all-out maximal cycling on a specialized ergometer, with 4 minutes of recovery in between, for a total of 2 to 3 minutes of intense exercise. The authors focused on specific markers in skeletal muscle metabolic control; they determined an increase in skeletal muscle oxidative capacity after 2 weeks of HIIT. They also found that changes in carbohydrate metabolism (Figure 2) were comparable to adaptations from endurance training. Although exercise performance improved, there was no measurable change in participants’ VO2peak after 2 weeks of HIIT. However, this study did not fully investigate how HIIT affects the cardiovascular and respiratory systems, or metabolic control in other organs.


Figure 2. Results depict the glycogen content, or resting carbohydrate dry weight, found in skeletal muscle during rest and 20 minutes after exercise, both before and after 2 weeks of HIIT.


Additional HIIT data concerning VO2peak and citrate synthase activity support the previous claim that HIIT provides similar benefits to endurance training. This review recognizes that Wingate-based training may not be tolerable for everyone, and instead tested low-volume HIIT. The authors found that their model was time-efficient and effective in producing cardiovascular and skeletal muscle adaptations. They reference the results of similar studies, saying that HIIT is superior to moderate-intensity continuous training (MICT)  in increasing cardiorespiratory fitness and endothelial function. However, researchers still don’t know what intensity or training volume is required to be effective.

A study concerning overweight and obese adults found that HIIT had similar results to MICT, in terms of body composition measures, but HIIT required less training time. They concluded that HIIT may be a time-efficient way to manage weight. Meanwhile, this systematic review determined that MICT and HIIT provide similar benefits for body fat reduction, but HIIT was no more time-efficient than MICT.

The data from these studies indicate that HIIT is comparable to MICT, similar to the difference between traditional and functional workouts, as described previously in this postHigh intensity workouts can be very demanding, as seen with the Wingate test, and may not be suitable for all individuals. HIIT should not be substituted for specialized athletic training, but can be beneficial for athletes who need to quickly use their bodily carbohydrates. Many HIIT studies are short-term, like the first study we mentioned, and further research needs to be conducted to determine the long-term effects of HIIT on cardiovascular and respiratory systems. Although HIIT attracts people with the allure of getting fit fast, there isn’t enough data currently to support that HIIT is actually more time-efficient than endurance training.

Questions to Consider:

Should HIIT workouts be recommended for the average person?

Why could an increase in glycogen dry weight be considered important for exercise?

How could your current workout routine benefit from HIIT?

What athletes do you feel would benefit most from HIIT?

Recommended Further Reading- Works Cited

  1. Figure 1. HiiT_40-20_6108. Attribution: Cathe Friedrich. [CC BY-NC-ND 2.0 (]
  2. Gibala, M. J., & McGee, S. L. (2008). Metabolic adaptations to short-term high-intensity interval training: A little pain for a lot of gain? Exercise and Sport Sciences Reviews, 36(2), 58-63. 10.1097/JES.0b013e318168ec1f
  3. Gibala, M. J., Little, J. P., MacDonald, M. J., & Hawley, J. A. (2012). Physiological adaptations to low-volume, high-intensity interval training in health and disease. The Journal of Physiology, 590(5), 1077-1084. 10.1113/jphysiol.2011.224725
  4. Wewege, M., van den Berg, R., Ward, R. E., & Keech, A. (2017). The effects of high-intensity interval training vs. moderate-intensity continuous training on body composition in overweight and obese adults: A systematic review and meta-analysis. Obesity Reviews, 18(6), 635-646. 10.1111/obr.12532
  5. Keating, S. E., Johnson, N. A., Mielke, G. I., & Coombes, J. S. (2017). A systematic review and meta-analysis of interval training versus moderate intensity continuous training on body adiposity. Obesity Reviews, 18, 943-964. 10.1111/obr.12536

How it Works: Direct Calorimetry


By Eryn Gerber, Destiny Neumann, & Andrew Reynolds

Suggested Reading/Works Cited:

G.P. Kenny et. al. Direct Calorimetry: a brief historical review of its use in the study of human metabolism and thermoregulation. Eur J Appl Physiol. (2017)

Calorimetry. ScienceDirect

Measuring Energy. Direct Calorimetry

V. Katch. Food and Physical Activity. Michigan Today (2013)

P. Pittet et al. Thermic effect of glucose in obese subjects studied by direct and indirect calorimetry. British Journal of Nutrition. (1976)

E.F. Bell et. al. Effect of body position on energy expenditure of preterm infants as determined by simultaneous direct and indirect calorimetry. Amer J Perinatol. (2017)


CrossFit vs. Bodybuilding, Apples to oranges or two sides to the same coin?

Recently workout fads have been popping up all over mainstream media and in different fitness centers. Everyone seems to have the ultimate plan to burn fat and build muscle, these routines have become more intricate and choreographed, often requiring a coach or instructor to oversee the work out. Older workout conventions have had to adapt to meet the changing needs and desires from society. We are here to figure out, is CrossFit the ‘glow up’ of Body building or are these two style of exercise completely unique?

First, what are CrossFit and bodybuilding?

Example of a typical CrossFit exercise

CrossFit is recognized as one of the fastest growing high intensity functional training regimens to date, popping up in 142 countries worldwide. But what is this mysterious new fad and does it actually work?  The purpose of CrossFit training is to get as ‘fit as personally possible’, but is not specifically focused on just one fitness area. CrossFit aims to optimize physical ability not only in strength, but in cardiovascular endurance, flexibility, power, speed, coordination, agility, balance, and accuracy as well [1]. This lead trainers to develop a plan that incorporates multiple training theories into one ‘Workout Of the Day’ to keep a variety of fitness elements working.These workouts involve elements from gymnastics, weightlifting, and cardiovascular exercises which are performed quickly with little rest between sets.

The goal of Bodybuilding (muscle specific) training is so lose as much fat content as possible while maximizing your bodies muscle mass. This kind of training is where terms like ‘leg day’ and ‘back day’ came from, it is devoting an entire workout to a few muscle groups and working them to exhaustion. When you undergo this type of training your body experiences hypertrophy of all muscle fiber types.[2] A bodybuilding workout focuses on keeping the heart rate steady and high weight low rep exercises to slowly break down and rebuild one’s muscle fiber. This is proven to be an effective method if one is only worried about shear size and growth of muscles [3].

Expected muscle growth of Bodybuilders

After hearing this do you believe they are the same? Here’s what science said.

The approaches of these two exercise styles are most definitely unique, but are the fitness results actually all that different? In one research study called “Functional vs. Strength Training in Adults” 101 subjects, averaging an age of about 55, were separated into two groups that each performed 24 sessions of (functional or strength) training protocol twice per week. Each subject was assessed before and after the study using a quantitative Y-balance test and a qualitative Functional Movement Screen test. The changes between pretest and post test were analyzed and results showed that there were no significant differences in improvement between the training protocols as a whole. However, functional training was less effective for women compared to men in the same group [4]. The variability in prior athletic training must be taken into consideration when interpreting these results. Some participants may have needed additional training to better their basic skills before partaking in these specific training protocols. 

Another study looked at ‘The effects of high-intensity intermittent exercise(HIIE) training on fat loss and fasting insulin levels of young women”[5] comparing the effects of CrossFit(HIIE) training to steady state weight lifting over the course of 15 weeks(exercising three times a week). While this study focused on insulin levels they reported a variety of information on lean body mass, fat content, and weight loss that can be used to draw conclusions about the exercise types as well, see that diet was not changed between the groups. This study showed that women who underwent the CrossFit style training showed a significant decrease in total body mass(they lost more weight) 3.5kg weight loss, compared to  the steady state weight lifters who showed a 0.5kg increase in body mass. Demonstrating that while CrossFit participants and bodybuilders may both be used for strenuous high demand exercise, CrossFit is a more effective method of losing weight whereas bodybuilding promotes the act of ‘bulking up.’ While this study was full of information, it does not completely validate the idea that Crossfit and Bodybuilding are the same results with a different method it does help share some information that can point future studies in the right direction.

Based on what we have found we can draw a similar conclusion to previous posts about these training styles. We concur with the groups from previous years that current studies show that while the methods of achieving a lower fat content are different, the overall outcomes of the training types are very similar. In order to better compare these two very different approaches to fitness, there needs to be more extensive research done. The current scientific literature related to CrossFit specifically is lacking. Few studies with high level of evidence at low risk of bias have been widely recognized [1]. As of now we cannot truly compare this new workout fad to the traditional bodybuilding without more extensive studies with conclusive evidence.

By; Ellen Dudzinski and Destiny Neumann

Questions to consider:

  1. Are CrossFit and bodybuilding the only ways to build muscle quickly and effectively?
  2. Is CrossFit or bodybuilding for everyone, why or why not?
  3. What athletes should attempt at least one of these training types?
  4. After reading this, how would you further evaluate the similarities and differences between CrossFit and bodybuilding?
  5. Would supplementation increase the results from either training style?

Suggested Readings:

Karavirta, L., M. P. Tulppo, D. E. Laaksonen, K. Nyman, R. T. Laukkanen, H. Kinnunen, A. Häkkinen, and K. Häkkinen. “Heart rate dynamics after combined endurance and strength training in older men.” Medicine and science in sports and exercise. July 2009. Accessed March 06, 2018.

Aagaard, P., and J. L. Andersen. “Effects of strength training on endurance capacity in top-level endurance athletes.” Scandinavian journal of medicine & science in sports. October 2010. Accessed March 06, 2018.

Fitts, R. H., and J. J. Widrick. “Muscle mechanics: adaptations with exercise-training.” Exercise and sport sciences reviews. Accessed March 06, 2018.

Fitts, R. H., D. R. Riley, and J. J. Widrick. “Functional and structural adaptations of skeletal muscle to microgravity.” The Journal of experimental biology. September 2001. Accessed March 06, 2018.