The validity and reliability of counter movement jump height measured with the Polar Vantage V2 sports watch.

The purpose of the present study was to assess the validity and reliability of the jump height measured by the Polar Vantage V2 sports watch in comparison to a gold-standard force plate measurement. Fifteen healthy adults, seven female, age 20-42 years participated in the study and performed six sets of three CMJs, on two consecutive days. The participants wore the Polar Vantage V2 sports watch (Polar Electro Oy, Kempele, Finland) whilst performing the jumps on two force plates (AMTI, Watertown, Massachusetts, United States).

The Validity and Reliability of Global Positioning System Units for Measuring Distance and Velocity During Linear and Team Sport Simulated Movements.

Huggins, RA, Giersch, GEW, Belval, LN, Benjamin, CL, Curtis, RM, Sekiguchi, Y, Peltonen, J, and Casa, DJ. The validity and reliability of GPS units for measuring distance and velocity during linear and team sport simulated movements. J Strength Cond Res 34(11): 3070-3077, 2020-This experimental study aimed to assess the validity and reliability of shirt-mounted 10-Hz global positioning system (GPS) units (Polar Team Pro) for measuring total distance (TD), constant velocity (VelC), and instantaneous velocity (VelI) during linear running and a team sport simulation circuit (TSSC).

Human running performance from real-world big data.

Wearable exercise trackers provide data that encode information on individual running performance. These data hold great potential for enhancing our understanding of the complex interplay between training and performance. Here we demonstrate feasibility of this idea by applying a previously validated mathematical model to real-world running activities of  ≈ 14,000 individuals with ≈ 1.

Triceps surae muscle-tendon properties in older endurance- and sprint-trained athletes.

Previous studies have shown that aging is associated with alterations in muscle architecture and tendon properties (Morse CI, Thom JM, Birch KM, Narici MV. Acta Physiol Scand 183: 291-298, 2005; Narici MV, Maganaris CN, Reeves ND, Capodaglio P. J Appl Physiol 95: 2229-2234, 2003; Stenroth L, Peltonen J, Cronin NJ, Sipila S, Finni T.

The effect of paired associative stimulation on fatigue resistance.

Unlabelled: Paired associative stimulation (PAS) is a non-invasive stimulation method developed to induce bidirectional changes in the excitability of the cortical projections to the target muscles. However, very few studies have shown an association between changes in motor evoked potentials (MEP) after PAS and behavioral changes in healthy subjects. In the present study we hypothesized that the functional relevance of PAS can be seen during fatiguing exercise, since there is always a central contribution to the development of fatigue.

Comparison of impact characteristics of four different ice hockey arena dasher boards.

During recent years the incidence of ice hockey related concussions has increased. Therefore, the main aim of this study was to determine how dasher board materials and structures affect impact characteristics and thereby concussion risk. The measurements were divided into two parts; 1.

Viscoelastic properties of the Achilles tendon in vivo.

It has been postulated that human tendons are viscoelastic and their mechanical properties time-dependent. Although Achilles tendon (AT) mechanics are widely reported, there is no consensus about AT viscoelastic properties such as loading rate dependency or hysteresis, in vivo. AT force-elongation characteristics were determined from 14 subjects in an ankle dynamometer at different loading rates using motion capture assisted ultrasonography.

Differences in contractile behaviour between the soleus and medial gastrocnemius muscles during human walking.

The functional roles of individual lower limb muscles during human walking may differ depending on walking speed or duration. In this study, 11 volunteers walked on a treadmill for 60 min at speeds corresponding to both optimal and 20% above optimal energetic cost of transport whilst oxygen consumption and medial gastrocnemius (MG) and soleus fascicle lengths were measured. Although energetic cost of transport was ∼12% higher at the faster speed, it remained constant over 60 min at both speeds, suggesting that humans can walk for prolonged periods at a range of speeds without compromising energetic efficiency.

Age-related differences in Achilles tendon properties and triceps surae muscle architecture in vivo.

This study examined the concurrent age-related differences in muscle and tendon structure and properties. Achilles tendon morphology and mechanical properties and triceps surae muscle architecture were measured from 100 subjects [33 young (24 ± 2 yr) and 67 old (75 ± 3 yr)]. Motion analysis-assisted ultrasonography was used to determine tendon stiffness, Young's modulus, and hysteresis during isometric ramp contractions.

Achilles tendon stiffness is unchanged one hour after a marathon.

Overuse-induced injuries have been proposed as a predisposing factor for Achilles tendon (AT) ruptures. If tendons can be overloaded, their mechanical properties should change during exercise. Because there data are lacking on the effects of a single bout of long-lasting exercise on AT mechanical properties, the present study measured AT stiffness before and after a marathon.

The optimal interstimulus interval and repeatability of paired associative stimulation when the soleus muscle is targeted.

Changes in the excitability of the cortical projections to muscles in the upper and lower limbs can be induced in the intact human by paired associative stimulation (PAS). An interstimulus interval (ISI) of 25 ms between peripheral nerve and transcranial magnetic stimuli has been found to be effective when targeting hand muscles. The optimal ISI to induce plasticity changes in the cortical projections to lower limbs is still not well established.

Neural compensation within the human triceps surae during prolonged walking.

During human walking, muscle activation strategies are approximately constant across consecutive steps over a short time, but it is unknown whether they are maintained over a longer duration. Prolonged walking may increase tendinous tissue (TT) compliance, which can influence neural activation, but the neural responses of individual muscles have not been investigated. This study investigated the hypothesis that muscle activity is up- or down-regulated in individual triceps surae muscles during prolonged walking.

In vivo mechanical response of human Achilles tendon to a single bout of hopping exercise.

Stiffness of the human Achilles tendon (AT) was determined in vivo before and after a single bout of hopping exercise. It was hypothesized, based on published data using in vitro specimens, that a reduction in AT stiffness may occur after just 1000 loading cycles at physiological stress levels. Ten healthy subjects performed two-legged hopping exercise consisting of 1150-2600 high impacts.

Achilles tendon length changes during walking in long-term diabetes patients.

Background: 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 tendinous tissues in the medial gastrocnemius muscle-tendon unit in long-term diabetes patients and control subjects during walking.

Neuromuscular fatigue induced by an isotonic heavy-resistance loading protocol in knee extensors.

The main aim of this study was to assess neuromuscular fatigue during a typical high-load, low-repetition loading protocol. Muscle stimulations were used to assess maximum voluntary contraction, resting single- and double-pulse twitch characteristics, and superimposed double-pulse twitch force (used to calculate voluntary activation) before and after an acute knee extension loading protocol. In our participants, who had previous resistance training experience, the mean voluntary activation level was 96.

Effect of time-of-day-specific strength training on maximum strength and EMG activity of the leg extensors in men.

In this study, we examined the effects of time-of-day-specific strength training on maximum strength and electromyography (EMG) of the knee extensors in men. After a 10-week preparatory training period (training times 17:00-19:00 h), 27 participants were randomized into a morning (07:00-09:00 h, n = 14) and an evening group (17:00-19.00 h, n = 13).

Effects of contraction intensity on muscle fascicle and stretch reflex behavior in the human triceps surae.

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 ; 250 degrees /s) were applied to the triceps surae at different moment levels (0-100% of maximal voluntary contraction). Surface EMG was recorded in the medial gastrocnemius, soleus, and tibialis anterior muscles, and ultrasound was used to measure medial gastrocnemius and soleus fascicle lengths.