Paavo V Komi

University of Jyväskylä | JYU · Department of Biology of Physical Activity

Aim: The specificity of muscle-tendon and foot architecture of elite Kenyan middle- and long-distance runners has been found to contribute to their superior running performance. To investigate the respective influence of genetic endowment and training on these characteristics, we compared leg and foot segmental lengths as well as muscle-tendon arc...

Without high impact forces, it is not clear how humans can utilize tendon elasticity during low-impact activities. The purpose of the present study was to examine the muscle-tendon behavior together with the electromyographic (EMG) activities of the vastus lateralis (VL) muscle during the human dolphin-kicking. In a swimming pool, each subject (n =...

The purpose of the present study was to examine characteristics of muscle anatomical cross-sectional area (CSA) for different regions from proximal to distal parts of each muscle of the hamstring muscles in high-level sprinters, and to examine the relationship with those and the sprint performance. The CSA of the semitendinosus (ST), semimembranosu...

Background Patients who have had an Achilles tendon (AT) rupture repaired are potentially at higher risk for re-rupture than those without previous rupture. Little attention has been given to the neuromechanical modulation of muscle–tendon interaction and muscle activation profiles during human dynamic movements after AT rupture repair. Objective T...

It has been reported that advancing age causes tendons to become more compliant and fascicles lengths shorter. This could then lead to enhancement of movement efficiency provided that the elderly adults can activate their muscles in the same way as the younger adults (YOUNG) during dynamic movements. The present study was designed to examine the ag...

The present study examined the effects of repetitive hopping training on muscle activation profiles and fascicle-tendon interaction in the elderly. 20 physically active elderly men were randomly assigned for training (TG) and control groups (CG). TG performed supervised bilateral short contact hopping training with progressively increasing training...

Purpose Leg muscle activation profiles and muscle–tendon interaction were studied with eleven internationally high-level Kenyan and eleven national level Japanese distance runners. Methods Ultrasonography and kinematics were applied together with surface electromyography (EMG) recordings of leg muscles when subjects ran on treadmill at 9.0 (SLOW) a...

Aging is related to a variety of changes at the muscular level. It seems that the age-related changes in motor unit activation are muscle- and intensity dependent. The purpose of this study was to examine the motor unit discharge rate (MUDR) in both isometric and dynamic contractions of the aging soleus muscle. Eight elderly males participated in t...

The superior success of East-African endurance runners has stimulated a large amount of interest in exploring valid reasons for their performance, especially for neuromuscular mechanics. This review provides a brief overview of classic neuromuscular interaction during running; and, thereafter, describes a specific neuromuscular interaction alternat...

Understanding the detailed control of human locomotion and balance can be improved, when individual motor units can be isolated and their firing rates followed in natural movement of large, fuctionally important muscles. For this reason the present study investigated the motor unit discharge rate (MUDR) in isometric and dynamic contractions of the...

Increasing age can influence the interaction of muscle fascicles and tendon during dynamic movements. The object of the present study was to examine occurrence and possible reasons for the age-specific behavior of fascicles and tendons and their interaction during hopping with different intensities. Nine young and 24 elderly subjects performed repe...

It is well documented that increasing effort during exercise is characterized by an increase in electromyographic activity of the relevant muscles. How aging influences this relationship is a matter of great interest. In the present study, nine young and 24 elderly subjects did repetitive hopping with maximal effort as well as with 50%, 65%, 75% an...

IntroductionBackground of Performance Potentiation in SSCWhat is the Best Movement to Demonstrate SSC?Instantaneous Force-Velocity Relationship during SSCDemonstration of Stretch Reflex Intervention in SSCDo Stretch Reflexes Have Time to be Operative in SSC?What is the Functional Significance of Stretch Reflexes in SSC?Task-Dependent Modulation of...

The aim of this study was to examine the influence of exercise-induced muscle damage on elbow rhythmic movement (RM) performance and neural activity pattern and to investigate whether this influence is joint angle specific. Ten males performed an exercise of 50 maximal eccentric elbow flexions in isokinetic machine with duty cycle of 1:15. Maximal...

The strong association between body mass and skeletal robusticity has been attributed to increasing skeletal loading with increasing mass. However, it is unclear whether body mass is merely a coarse substitute for bone loading rather than a true independent predictor of bone strength. As indices of neuromuscular performance, impulse and peak power...

Diabetes leads to numerous side effects, including an increased density of collagen fibrils and thickening of the Achilles tendon. This may increase tissue stiffness and could affect stretch distribution between muscle and tendinous tissues during walking. The primary aim of this study was to examine stretch distribution between muscle and tendinou...

Bone response to a single bout of exercise can be observed with biochemical markers of bone formation and resorption. The purpose of this study was to examine the response of bone biochemical markers to a single bout of exhaustive high-impact exercise. 15 physically active young subjects volunteered to participate. The subjects performed continuous...

After repeated passive stretching, tendinous tissue compliance increases in the human soleus (SOL) muscle-tendon unit. During movement, such changes would have important consequences for neural and mechanical stretch responses. This study examined the existence of such effects in response to a 75 min walking intervention. Eleven healthy subjects wa...

During human walking, a sudden trip may elicit a Ia afferent fibre mediated short latency stretch reflex. The aim of this study was to investigate soleus (SOL) muscle mechanical behaviour in response to dorsiflexion perturbations, and to relate this behaviour to short latency stretch reflex responses. Twelve healthy subjects walked on a treadmill w...

The present study utilized high-impact supra-maximal landings to examine the influence of the pre-impact force level on the post-impact electromyographic (EMG) activity and, in particular, on the short latency EMG reflex (SLR) component. Unilateral-leg landings were performed in a sitting position on a sledge apparatus after release from high, but...

Eccentric exercise induced by electrostimulation increases mRNA expression of titin-complex proteins in rodent skeletal muscle. In this study, mRNA expression of titin, muscle LIM protein (MLP), cardiac ankyrin repeat protein (CARP), ankyrin repeat domain protein 2 (Ankrd2), diabetes-related ankyrin repeat protein (DARP), and calcium-activated prot...

High-speed ultrasonography has revealed that, in human locomotion, the nature of fascicle and tendon length changes varies depending on the task, contraction intensity, and the muscles involved. The findings emphasize that the active fascicles of the gastrocnemius muscle are suddenly stretched, although they are shortening. This short-lasting stret...

The aims of this study were to examine changes in the distribution of a stretch to the muscle fascicles with changes in contraction intensity in the human triceps surae and to relate fascicle stretch responses to short-latency stretch reflex behavior. Thirteen healthy subjects were seated in an ankle ergometer, and dorsiflexion stretches (8 degrees...

The present study characterized pole and ski forces in classical technique cross-country skiing. Eight elite junior cross-country skiers performed diagonal skiing at 65%, 75%, 90%, and 100% of maximum speed on a stable 100-m-low uphill (2.5 degrees ). : The ski and the pole forces (vertical (Fz) and horizontal (Fy) directions) on the right and left...

The excitability of short-latency stretch reflex can be improved after the stretch shortening cycle exercises. This can influence the force exerted by muscle during the shortening contraction phase. In addition, it could also cause changes of the Achilles tendon (AT) behavior in such a training. PURPOSE: The purpose of the present study was to exam...

IntroductionBiomechanical equipmentBiomechanical analysisExamples of biomechanical investigationsSummaryMultiple choice questions

This chapter contains section titled:

IntroductionMethods to study in vivo tendon loadingTensile loading and locomotionClinical relevance and significanceFuture directions

Effects of an exhaustive eccentric exercise (EE) on the motor control of maximal velocity rhythmic elbow extension/flexion movement (RM) were examined in eight male students. The exhaustive EE consisted of 100 maximal eccentric actions of the elbow flexor muscles. Movement range was 40-170 degrees in EE at an angular velocity of 2rads(-1). A direct...

High mechanical loading was hypothesized to induce the expression of angiogenic and/or lymphangiogenic extracellular matrix (ECM) proteins in skeletal muscle. Eight men performed a strenuous exercise protocol, which consisted of 100 unilateral maximal drop jumps followed by submaximal jumping until exhaustion. Muscle biopsies were taken 30 min and...

Repetitive impulsive forces during walking are claimed to result in joint osteoarthritis (OA). The aim of this study was to investigate impact loading and gait symmetry during level and stair walking in asymptomatic elderly subjects with knee OA. It was hypothesised that pre-activity of the quadriceps femoris muscle (QF) would be an important facto...

Recovery of force and stretch reflex from exhaustive stretch-shortening cycle (SSC) exercise is usually bimodal, characterized as immediate exercise-induced performance reduction, with its quick recovery followed by a longer-lasting reduction in performance. A clear parallel exists between the respective changes in performance, neural activation, a...

Neuromuscular fatigue has traditionally been examined using isolated forms of either isometric, concentric or eccentric actions. However, none of these actions are naturally occurring in human (or animal) ground locomotion. The basic muscle function is defined as the stretch-shortening cycle (SSC), where the preactivated muscle is first stretched (...

When the prestretch intensity and concentric work are increased in stretch-shortening cycle (SSC) exercises, the utilization of the elastic energy can increase during the concentric phase. In order to further understand this process during SSC exercises, the interaction between fascicle-tendinous tissues (TT) of the vastus lateralis (VL) muscle was...

In several explosive types of sport events the leg extensor muscles are subjected to very high impact loads. Thus, extreme requirements exist for the neuromuscular system to develop sufficient muscle stiffness in the lower extremities in order to tolerate these high impact loads. Therefore, it would be challenging to measure reflex modulation durin...

The aim of this study was to examine the effects of muscle-tendon length on joint moment and power during maximal sprint starts. Nine male sprinters performed maximal sprint starts from the blocks that were adjusted either to 40 degrees or 65 degrees to the horizontal. Ground reaction forces were recorded at 833 Hz using a force platform and kinema...

Neuromuscular fatigue has traditionally been examined using isolated forms of either isometric, concentric or eccentric actions. However, none of these actions are naturally occurring in human (or animal) ground locomotion. The basic muscle function is defined as the stretch-shortening cycle (SSC), where the preactivated muscle is first stretched (...

Electromyographic (EMG) activity of the leg muscles and the ground reaction forces were recorded in 17 elite male middle-distance runners, who performed isometric maximal voluntary contractions (MVC) as well as running at different speeds. Electromyograms were recorded from the gluteus maximus, vastus lateralis, biceps femoris, gastrocnemius and ti...

The present study was designed to explore how the interaction between the fascicles and tendinous tissues is involved in storage and utilization of elastic energy during human walking. Eight male subjects walked with a natural cadence (1.4 +/- 0.1 m/s) on a 10-m-long force plate system. In vivo techniques were employed to record the Achilles tendon...

The purpose of this study was to examine acute hormonal and neuromuscular responses in men and women to 3 heavy resistance but clearly different exercise protocols: (a) submaximal heavy resistance exercise (SME), (b) maximal heavy resistance exercise (HRE), and (c) maximal explosive resistance exercise (EE). HRE included 5 sets of 10 repetition max...

This study examined acute and long-lasting effects of fatigue and muscle damage on fast and accurate elbow flexion and extension target movements (TM) with eight male students. An isokinetic machine was used to perform 100 maximal eccentric and concentric elbow flexions at 4-week intervals. Movement range was 40-170 degrees in eccentric exercise (E...

Experiments were carried out to examine interaction between mechanical changes of the muscle-tendon unit and reduced reflex sensitivity after repeated and prolonged passive muscle stretching (RPS). There is some evidence that this interaction might be relevant also during active stretch-shortening cycle type of fatigue tasks. The results demonstrat...

This study examined whether the elasticity of the tendinous tissues plays an important role in human locomotion by improving the power output and efficiency of skeletal muscle. Ten subjects performed one-leg drop jumps (DJ) from different dropping heights with a constant rebound height. The fascicle length of the vastus lateralis muscle was measure...

Seven young patients were followed 52 weeks after intramedullary lengthening for limb length discrepancy (LLD). The mean LLD before surgery was 3.0 +/- 1.1 cm and 1 year after surgery at the time of the nail-removal it was 0.3 +/- 0.3 cm. The plantar pressures and the ground reaction forces (GRF) were recorded simultaneously with electromyographic...

The aim of this study was to assess the effects of a resistance exercise session (RES) on free amino acid concentrations and protein synthesis and breakdown of the vastus lateralis (VL) muscle during recovery in male subjects. Both the exercise group (EG) and the control group (CG) consisted of six healthy physically active men. On the experiment d...

PITKÄNEN, H. T., T. NYKÄNEN, J. KNUUTINEN, K. LAHTI, O. KEINÄNEN, M. ALEN, P. V. KOMI, and A. A. MERO. Free Amino Acid Pool and Muscle Protein Balance after Resistance Exercise. Med. Sci. Sports Exerc., Vol. 35, No. 5, pp. 784-792, 2003. Purpose: The aim of this study was to assess the effects of a resistance exercise session (RES) on free amino ac...

KYRÖLÄINEN, H., R. KIVELÄ, S. KOSKINEN, J. MCBRIDE, J. L. ANDERSEN, T. TAKALA, S. SIPILÄ, and P. V. KOMI. Interrelationships between Muscle Structure, Muscle Strength, and Running Economy. Med. Sci. Sports Exerc., Vol. 35, No. 1, pp. 45-49, 2003. Purpose: The present study was designed to investigate possible differences in running economy (RE) amo...

The present study was designed to investigate possible differences in running economy (RE) among elite middle-distance runners by examining muscle structure and maximal isometric force (MVC). Ten young male runners ran at six different running speeds. During the running bouts, respiratory gases, and blood lactate were measured. Muscle biopsies were...

Hormonal responses to an unaccustomed knee-extension exercise (E1; 5 times 10 repetitions with 40% load of 1RM [1 repetition maximum] followed by 2 sets until exhaustion) were compared in 6 men with the corresponding responses to an identical exercise performed 2 days later under the influence of delayed onset muscle soreness (DOMS) (E2). Both exer...

The purpose of this study was to examine power-type athletes to determine changes in amino acid and hormone concentrations in circulating blood following 2 different high-intensity exercise sessions before and after the 5-week training period. Eleven competitive male sprinters and jumpers performed 2 different running exercise sessions: a short run...

This study was designed to investigate the acute plasma catecholamine (CA) response to resistance exercise and its association with serum testosterone (TES), cortisol (COR), and growth hormone (GH) concentration changes. Six men, six women, and six adolescent boys (14 +/- 0 yr) performed five sets of 10 knee extensions with 40% of one-repetition ma...

The problems in comparing the performances of Olympic weightlifters arise from the fact that the relationship between body weight and weightlifting results is not linear. In the present study, this relationship was examined by using a nonparametric curve fitting technique of robust locally weighted regression (LOWESS) on relatively large data sets...

Stiffness has often been considered as a regulated property of the neuromuscular system. The purpose of this study was to examine the ankle and knee joint stiffness regulation during sprint running. Ten male sprinters ran at the constant relative speeds of 70, 80, 90, and 100% over a force platform, and ground reaction forces, kinematic, and EMG pa...

Different profiles of ski jumping hills have been assumed to make the initiation of take-off difficult especially when moving from one hill to another. Neuromuscular adaptation of ski jumpers to the different jumping hills was examined by measuring muscle activation and plantar pressure of the primary take-off muscles on three different sized hills...

Length changes in vastus lateralis fascicles were measured in vivo using ultrasonography during one-legged squat jumps (SJ), counter movement jumps (CMJ), and drop jumps (DJ) in the sledge apparatus (n = 9). Patellar tendon forces were recorded simultaneously with an optic fiber technique from 4 subjects. Fascicle length changes were compared with...

Central fatigue was investigated under an isolated active condition whereby the possible effects of supraspinal fatigue were minimized. Therefore, ten subjects were fatigued by simultaneously and repeatedly mechanically stretching and electrically stimulating their calf muscles for 1h. This was performed using an ankle ergometer. The active fatigue...

The effects of movement amplitude and contraction intensity on triceps surae and quadriceps femoris muscle function were studied during repetitive hopping. In vivo forces from Achilles and patellar tendons were recorded with the optic fibre technique from eight volunteers. The performances were filmed (200Hz) to determine changes in muscle-tendon u...

An optic fibre method was used to measure in humans in vivo Achilles (ATF) and patellar tendon forces (PTF) during submaximal squat jumps (SJ) and counter movement jumps (CMJ). Normal two-legged jumps on a force plate and one-legged jumps on a sledge apparatus were made by four volunteers. Kinetics, kinematics, and muscle activity from seven muscle...

Low exercise-induced plasma adrenaline (A) responses have been reported in resistance-trained individuals. In the study reported here, we investigated the interaction between strength gain and neural adaptation of the muscles, and the plasma A response in eight healthy men during a short-term resistance-training period. The subjects performed 5 res...

Knowledge of muscle actions is essential for understanding biomechanics in running. In this study, 17 young runners were investigated at 13 different running speeds. Telemetric surface electromyograms from lower leg muscles were recorded continuously, and they were synchronized with the recordings of 3-dimensional ground reaction forces from a 10-m...

The plasma adrenaline ([A]) and noradrenaline ([NA]) concentration responses of nine men and eight women were investigated in four resistance exercise tests (E80, E60, E40 and E20), in which the subjects had to perform a maximal number of bilateral knee extension-flexion movements at a given cycle pace of 0.5 Hz, but at different load levels (80%,...

Effects of a 12-week power training of upper limbs on neuromuscular performance and mechanical efficiency (ME) was studied in 7 women. Isometric maximum, pure concentric (Cone), pure eccentric (Ecc), and stretch-shortening cycle (SSC) exercises with maximal and submaximal efforts were undertaken. The results showed that improvement in maximal perfo...

It has been suggested that during repeated long-term stretch-shortening cycle (SSC) exercise the decreased neuromuscular function may result partly from alterations in stiffness regulation. Therefore, interaction between the short latency stretch-reflex component (M1) and muscle stiffness and their influences on muscle performance were investigated...

The plasma noradrenaline (NA) and adrenaline (A) concentration responses of seven young male athletes [15 (SD 1) years] and seven adult male athletes [25 (SD 6) years] were investigated together with the serum testosterone (Tes) concentration responses in four different half-squatting exercises. The loads, number of repetitions, exercise intensity...

Neural, mechanical and muscle factors influence muscle force production. This study was, therefore, designed to compare possible differences in the function of the neuromuscular system among differently adapted subjects. A group of 11 power-trained athletes and 10 endurance-trained athletes volunteered as subjects for this study. Maximal voluntary...