PROathlete Talk #05 with Muscle Researcher Prof. Per Tesch

Per-TeschIn this episode we welcome the muscle researcher Per Tesch from the Karolinska Institute and nHANCE, Stockholm. He is a researcher, founder, and sport scientific advisor with an impressive track record. The American College of Sports Medicine announced him as a fellow. Besides his research awards of renowned institutes (NASA, ESA, NIH), he has also achieved practical merits like the Olympic silver medal as coach and sport scientific advisor. Beyond that, he is the co-founder of the Tesch & Övermo foundation, that aims to foster muscle health.
My mentor Henk Kraaijenhof introduced me to the work of Per several years ago. In the meantime, I integrated some of his outstanding findings successfully into my toolbox. In this conversation, we are talking about Per´s muscle research, his unique career and possible applications of the eccentric overload concept.

„The eccentric action is part of normal locomotor activities and should not be viewed as a separate action.“

In more detail:

  • We are talking about his NASA research
  • Future research challenges
  • Per explains some aspects of the eccentric muscle action and the eccentric-overload concept

Per, your muscle research affects the preparation routines of athletes, bodybuilders, and astronauts. However, it was a long journey. Please tell us how your professional career started. What was your motivation in the early days of your career?

Per Tesch: Early on, I was dedicated to almost any sport but in particular ice-hockey and skiing. I had an athletic career as a flat-water kayaker. This brought me to the College of Physical Education (GIH), Stockholm. My interest in exercise physiology was spurred by teachers and giant research professors at GIH at the time. In this regard, I have to mention Per-Olof Åstrand, Bengt Saltin, and Jan Karlsson. Jan Karlson, my main tutor, was a most influencial in my career being an exceptional energetic, smart, and creative research coach. Hence, I decided not to teach physical education, but rather to devote my life to research! My initial applied research project explored the physiology of competitive kayaking. Over the years and in spare time I served as an exercise physiology consultant to numerous professional and high-caliber athletes and was the personal coach of a world champion and 1992 Olympic silver medalist kayaker. Also, I developed and applied physiological testings to monitor and advise the very successful Swedish national kayak team in these years.

In 1980, you received your Ph.D. at the Karolinska Institute Stockholm. How has your research interest changed over the time?

PT: Central to my research from the beginning was the use of the muscle biopsy technique to study skeletal muscle metabolism and morphology in response to acute and chronic, mainly high-intensity exercise. My doctoral thesis was about ”Muscle Fatigue with special reference to lactate accumulation during short-term high intensity exercise in fast and slow twitch fibers of human skeletal muscle”, and included laboratory as well as field experiments, e.g., alpine skiing. I did my postdoc training at the US Army Research of Environmental Medicine (USARIEM), Natick (Boston), MA from 1979 to 1980, and meanwhile, served as a lecturer at Boston College. I introduced the biopsy technique and established a human muscle biology and exercise performance laboratory at USARIEM, to help explain features critical to physical performance in war fighters. Thus, my early muscle and exercise research was devoted to studies of lactate and anaerobic metabolism and the influence of fiber type composition on performance. Soon my research focus was shifted to exploring various aspects of acute and chronic neuromuscular adaptations to resistance training – at that time a neglected, and almost a non-existing research field.

I decided to return to Stockholm and the Karolinska Institute after being awarded a major grant by the Swedish Royal Air Force to study the effects of strength training on g-tolerance in fighter pilots. As a result of these efforts, all Swedish air force bases were equipped with gyms using specific strength training methods, which I prescribed. Soon, many other air forces around the globe followed and applied strength training as a means to improve g-tolerance in pilots during aerial combat maneuvers. In the year 1983, I received my docentureship in physiology at the Karolinska Institute.

Per, in the 90s you worked for the NASA. Can you expand more on this, please?

„The Yo-Yo concept offers eccentric overload only in a selected range of motion, not through the entire range of motion.“

PT: Dr. Paul Buchanan, one of the medical doctors serving the very first astrounauts, recruited me to NASA’s Kennedy Space Center (KSC), Cape Canaveral, Florida, to be part of a team asked to establish a world-leading muscle and exercise countermeasures research program. My mission at KSC was manyfold. First, to learn more about how skeletal muscle adapts to weight training with or without eccentric actions. Secondly, to develop a ”simple” ground-based simulation model, to replace the very costly bed-rest model, to induce skeletal muscle atrophy, similar to that which occurs in space. Thirdly, to develop a compact non-gravity dependent exercise apparatus, simulating the effects of weight training, that could be used in space by astronauts to combat muscle and bone loss.

That sounds like an exciting and intense part of your career.

PT: Yes, that is true. Unfortunately, political decisions in Washington ended this very successful program a few years later. Anyway, my work and interaction with astronauts, engineers and research partners at KSC inspired me, and together with my former Ph.D. student, Dr. Hans Berg we developed, validated and patented the inertial flywheel technology branded YoYoTM (currently nHANCETM driven by YoYo Technology). We published numerous research papers demonstrating supporting its use in space. In 1994, Muscle & Fitness published a feature high-lighting our novel technology and displayed the very first configuration (the YoYoTM Leg Press) advocating the more broad applications (e.g., athletes, bodybuilders, fitness).

In the 70’s commercial isokinetic machines (based on a patent by James Perrine of UCLA) were introduced. In many of our reserach stuides we used the ”state of the art” Cybex machine, for testing and training. Back then the technology only allowed foir concentric actions. There were some obvious drawbacks which, over time, I became less enthusiastic about, but also spurred my interest to further study resistance exercise using concentric  actions only produces limited responses.

Can you name a few of these ”negatives”?

PT: Firstly, the translation of increases in concentric force and power to more important neuro-physiological adaptations are poor. Moreover, isokinetic concentric, but also coupled isokinetic concentric and eccentric actions, show compromised muscle protein synthesis compared with non-isokinetic training.

Ok, I understand. Per, what happend next with your research?

PT: The YoYoTM leg press was used in experiments on the astronauts who flew the STS 78 Space Shuttle mission in 1996. We then designed and validated the more versatile YoYoTM MultiGym to be used by NASA on long-haul missions. This configuration was used by my research team and others in bedrest studies up to 90-day long. Thus men and women confined to bed used the machine to combat muscle atrophy. We also employed this device in men who were confined for 110-d in a very small space module, in a project we carried out in Moscow in collaboration with the Russian Space Agency.

In 1996, I was instrumental in developing and introducing the unilateral unloading model (ULLS); an analog to simulate skeletal muscle and bone unloading in space (cf. review paper published by the Journal of Applied Physiology in 2016). A major NASA award allowed me to carry out the ”ultimate study” to prove YoYoTM exercise combats muscle atrophy during simulated 0-g exposure, at the University of Arkansas for Medical Sciences, Little Rock from 1999 until 2001. Men and women were subjected to ULLS for five weeks resulting in unloading of the knee extensors. Half of the subjects performed YoYoTM exercise (five sets of seven reps) two or three times a week on a YoYoTM knee extensor machine. The major atrophy (9%) showed after ULLS was not only prevented! Trainees did, in fact, show a robust 9% increase in muscle size!

Let us shift the focus to the more specific questions. I would like to talk with you about muscle actions, the eccentric overload concept, and practical applications. To summarize briefly, what are the main features of the eccentric action?

PT: First, please ackowledge that the eccentric action is a natural part of ordinary locomotor activities and should not be viewed as a separate action. The stretch (eccentric)- shortening (concentric) cycle is fundamental in the majority of our daily activities. The eccentric action inherently offers higher tension than the concentric action and at a much less of energy. The more significant tensional stress of the eccentric contraction is a powerful stimulus for muscle protein synthesis. Also, the stretch is typically associated with eccentric muscle actions. Research results convincingly suggest there is a unique neural strategy during eccentric actions, and the proprioceptive stimulus is much greater with eccentric actions.

Per, your name is often related to the eccentric overload concept. Would you be so kind and outline some details?

PT: Indeed, I didn´t come up with this! The idea of offering more ”load” in the eccentric phase is not new. Bodybuilding magazines and Russian training literature, for instance, has advised ”negatives” or ”forced reps” for generations of athletes using barbells, dumb bells with the aid of spotters. In contrast, with YoYoTM eccentric overload is offred only in a selected range of motion – not through the entire range of motion. It should be understood the energy produced during concentric and eccentric actions of a cycle is the same.

What do you think, who were the first adopters of the concept?

PT: Professors Komi and Buskirk published a paper in 1972. The study they conducted at Penn State University, using a motor driven machine, showed the superiority of eccentric overload training. I would like to say their piece of work was pioneer research in the field. There were other research groups at the time also exploring the benefits of concentric and eccentric exercise and inferring the benefits of eccentric training.

That is more than 40 years ago. Another reason to study the old pioneering research pieces. Nowadays, in elite sports, injury prevention has become a severe problem. For instance, hamstring injuries are a hot topic. The Nordic hamstring exercise has been described as an exercise oriented prevention approach. What are the benefits of flywheel-exercises over Nordic hamstring exercise?

PT: In brief, exercises like the YoYoTM leg curl involves more muscle mass and shows much higher muscle activity than the Nordic hamstring exercise. The YoYoTM leg curl induces marked muscle activity of all individual hamstring muscles, plus the gracilis. Not the Nordic hamstring exercise. The Nordic hamstring exercise is not a ”coupled” concentric-eccentric action; and it is executed at slow, very non-functional speed. The YoYoTM leg curl offers greater peak tension and a much more significant stretch.

What recommentations do you have for the prevention of hamstring injuries?

PT: Regardless, if the eccentrics consist of plyometrics or iso-inertial YoYoTM training, have patience! Progress slowly with regard to frequency, intensity, and volume and ensure more than 48 hours recovery between sessions.

We have entered the summit of our conversation, yet. Per, I want to close with the question, what literature and courses do you suggest?

PT: Select appropriate key words and go to ”PubMed”, there you can find anything that is worth reading. I would also recommend the recent book of Swiss Professor Hans Hoppeler entitled ”Eccentric Exercise”. This is a good source of literature in my view. We offer the course ”Certified Eccentrics by nHANCE”. The Annual Global Hamstring Project is a great meeting to attend, and learn more, and share and discuss with the best coaches and other practitioners and researchers (

Per, thank you for your insights. It was a pleasure.

QUESTION OF THE EPISODE: What was your favourite statement or lesson? Let us know your comments.

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