Discipline-specific Torque-Velocity Profiles and Musculotendinous Morphology in Athletes.

OBJECTIVES: The aim of this study was to compare torque-velocity profiles, muscle architecture, tendon dimensions, and bilateral-symmetry between competitive cyclists (CY), competitive runners (RN), ice-hockey players (IH), basketball players (BP), and physically-active individuals (CN) (n=10 for each group). METHODS: Vastus lateralis (VL) muscle and patellar tendon (PT) structures were determined with B-mode ultrasonography, and maximal knee extensor isokinetic torque was assessed at three different velocities. RESULTS: Optimal torque and velocity were lower in runners than CY, BP and IH (p<0.05). Maximal power was similar between the athlete groups but greater than CN (p<0.05). Furthermore, RN and BP reached their peak-torque at longer muscle lengths compared to IH and CY (p<0.05). RN had the lowest VL muscle thickness and the greatest fascicle length, while CY had the greatest pennation angle (p<0.05). CY had the greatest PT thickness, particularly at the proximal and medial sites, while BP at the distal point (p<0.05), with similar trends observed for PT cross-sectional-area. CONCLUSIONS: Our findings show that even if power generating capacity is similar between athletic disciplines, there are discipline-specific muscle adaptations, where particularly runners appear to have muscles adapted for speed rather than torque development, while in cyclists, velocity is sacrificed for torque development.

Increasing the resting time between drop jumps lessens delayed-onset muscle soreness and limits the extent of prolonged low-frequency force depression in human knee extensor muscles.

PURPOSE: Unaccustomed eccentric contractions generally result in a long-lasting contractile impairment, referred to as prolonged low-frequency force depression (PLFFD), and delayed-onset muscle soreness (DOMS). We here used repeated drop jumps (DJs) as an eccentric contraction model and studied the effects of increasing the time between DJs from 20 s to 5 min. We hypothesized that both PLFFD and DOMS would be less marked at the longer DJ interval due to the longer time to restore structural elements between DJs. METHODS: Young men (n = 12) randomly performed 50 DJs with either 20-s (DJ-20 s) or 5-min (DJ-5 min) rest between DJs. Voluntary, 20 Hz and 100 Hz electrically stimulated isometric knee extension torques and muscle soreness were monitored before and for 7 days after DJs; serum CK activity was measured to assess muscle fibre protein leakage. In additional experiments, changes in mRNA levels were assessed in muscle biopsies collected before and 1 h after exercise. RESULTS: A marked PLFFD was observed with both protocols and the extent of 20 Hz torque depression was smaller immediately and 1 day after DJ-5 min than after DJ-20 s (p < 0.05), whereas the MVC and 100 Hz torques were similarly decreased with the two protocols. Markedly larger differences between the two protocols were observed for the muscle soreness score, which 1-4 days after exercise was about two times larger with DJ-20 s than with DJ-5 min (p < 0.01). CONCLUSIONS: The larger protective effect of the longer DJ interval against DOMS than against PLFFD indicates that their underlying mechanisms involve different structural elements.

Acute effects of high-intensity interval training on cognition and retinal microcirculation in experienced amateur boxers.

BACKGROUND: Limited and contradictory data are available regarding the acute effects of endurance exercises on cognition and retinal microcirculation. Thus, we aimed to evaluate the acute effects of sport-specific high-intensity interval training (HIIT) on cognition and retinal vessel diameters in experienced amateur boxers. METHODS: Eleven young (age 22.8±2.9 years) men with 10.7±4.8 years of boxing experience completed two sessions in random order: high-intensity intermittent punching load and passive rest. Cardiovascular response, retinal vessel diameters, and cognitive performance were evaluated at baseline, during exercise, and immediately after each session. RESULTS: Increased heart rate during intermittent punching load (P<0.05) reaching 91.2±3.7% of the maximal heart rate was observed. The HIIT improved cognitive flexibility and inhibitory control (P<0.05), while the working memory and motor speed were not affected. Significant dilatation of temporal retinal venules (P<0.05) was observed after the HIIT compared with the values before the HIIT, resulting in a decreased arteriolar-to-venular diameter ratio (P<0.05). CONCLUSIONS: At the functional level, an improvement in executive function due to intermittent high intensity punching load was observed, while at the physiological level, retinal venular dilatation was observed in experienced amateur boxers.

The contribution of low-frequency fatigue to the loss of quadriceps contractile function following repeated drop jumps.

NEW FINDINGS: What is the central question of this study? Why do some subjects recover slowly following a bout of eccentric exercise and why is recovery faster following a repeated bout? What is the main finding and its importance? The results are consistent with two major causes of the reduction of quadriceps torque, the onset of low-frequency fatigue which recovered relatively fast and a second, delayed form of damage. Differences in the delayed damage process largely accounted for the differences in the rate of torque recovery between subjects after a first bout and it was suppression of the delayed damage which accounted for the faster recovery following a repeated bout of eccentric exercise. ABSTRACT: The purpose of this study was to determine the extent to which low-frequency fatigue (LFF) accounts for the loss of quadriceps strength and time course of recovery following a series of drop jumps (DJs). Seventeen female subjects (20.8 ± 1.4 years) undertook 100 DJs, which were repeated 4 weeks later. Maximum isometric torque (MIT) and the ratio of torque generated by 20 and 100 Hz electrical stimulation (20/100), as a measure of LFF, were measured over 7 days following each series of DJs. After the first series the 20/100 ratio fell to a greater extent than MIT (to 35 ± 8.7% and 69 ± 11%, respectively) but recovered over 2-3 days, while MIT showed little recovery over this time. Changes of the 20/100 ratio were similar between subjects with fast or slow MIT recovery. Following the second series of DJs, changes in the 20/100 ratio were similar to those of the first bout and there were no differences between fast and slow recovering subjects. MIT, however, recovered more rapidly than after the first bout; the faster recovery was confined to the subjects who recovered slowly following the first bout. The results are consistent with two major causes of the reduction of quadriceps torque, the onset of low-frequency fatigue which recovered relatively fast and a second, delayed, form of damage. The latter largely accounted for the differences in MIT recovery between subjects after the first bout, while suppression of the delayed damage accounted for the faster recovery following the repeated bout.

Acute and chronic effects of soccer game on the retinal vessel diameters in middle-aged adults.

BACKGROUND: Although changes in retinal vessel diameter is a new biomarker for the evaluation of cardiovascular risk factors, limited information is available regarding the effects of endurance exercises on retinal microcirculation. Thus, we aimed to evaluate both chronic and acute effects of soccer game on the diameters of retinal vessels in middle-aged players. METHODS: Retinal vessel diameters were measured in 12 middle-aged amateur players (44.4±7.0 years of age) with more than four years of soccer playing experience and 12 age-matched sedentary adults (49.7±7.1 years of age). In soccer players, diameters were also measured immediately after the soccer game. Cardiovascular risk profiles (anthropometry and body composition and blood pressure [BP]) and physical activity levels were also measured. RESULTS: Soccer players had wider retinal vessels than controls (P<0.05), resulting in greater arteriolar-to-venular diameter ratio (AVR) (P<0.05). Greater sports-related physical activity, lower body mass index (BMI) and fat mass were observed for soccer players compared to the controls (P<0.05), whereas BP did not differ. Physical activity level correlated positively with temporal retinal arteriolar (TRA) diameter and with AVR (P<0.05), whereas TRA diameter correlated negatively with BMI and fat mass (P<0.05). A significant correlation between temporal retinal venule (TRV) diameter and TRA diameter (P<0.05) was observed. The acute soccer game increased BP (P<0.05) and induced TRV dilatation (P<0.05). CONCLUSIONS: In middle-aged amateur soccer players, improvement of the retinal microcirculation was observed. Cardiovascular risk factors and physical inactivity were associated with adverse retinal microvascular alterations. In terms of acute effects, soccer play causes venular, but not arteriolar dilatation for middle-aged adults.

Effects of age and sex on fatigability and recovery from a sustained maximal isometric voluntary contraction.

The aim was to assess the effects of sex and age on fatigability and recovery from sustained maximal voluntary contraction (MVC) of the knee extensor muscles. The central (central activation ratio (CAR) and electrical activity amplitude) and peripheral (electrically evoked torque and muscle contractile properties) factors contributing to fatigue and recovery of 24 young adults (12 males) aged 23.2±3.6years and 20 older adults (12 males) aged 70.6±4.4years were compared. The increase in central and peripheral fatigue was greater (p⩽0.01) in the young adults vs the older adults. Sex differences (p=0.002) regarding MVC were attributed to the greater (p<0.01) peripheral fatigue of males vs females. The recovery rate of MVC was greater (p<0.001) in the young adults vs the older adults, with no sex effect. The recovery of MVC was correlated with the CAR in older adults (p=0.001). Thus, the greater endurance observed with age is caused by differences in central and peripheral mechanisms, whereas the greater endurance in females is caused by a difference in a mechanism located within the muscle. The impaired recovery from fatigue in older adults relied more on the recovery of central factors.

Interval Running Training Improves Cognitive Flexibility and Aerobic Power of Young Healthy Adults.

Venckunas, T, Snieckus, A, Trinkunas, E, Baranauskiene, N, Solianik, R, Juodsnukis, A, Streckis, V, and Kamandulis, S. Interval running training improves cognitive flexibility and aerobic power of young healthy adults. J Strength Cond Res 30(8): 2114-2121, 2016-The benefits of regular physical exercise may well extend beyond the reduction of chronic diseases risk and augmentation of working capacity, to many other aspects of human well-being, including improved cognitive functioning. Although the effects of moderate intensity continuous training on cognitive performance are relatively well studied, the benefits of interval training have not been investigated in this respect so far. The aim of the current study was to assess whether 7 weeks of interval running training is effective at improving both aerobic fitness and cognitive performance. For this purpose, 8 young dinghy sailors (6 boys and 2 girls) completed the interval running program with 200 m and 2,000 m running performance, cycling maximal oxygen uptake, and cognitive function was measured before and after the intervention. The control group consisted of healthy age-matched subjects (8 boys and 2 girls) who continued their active lifestyle and were tested in the same way as the experimental group, but did not complete any regular training. In the experimental group, 200 m and 2,000 m running performance and cycling maximal oxygen uptake increased together with improved results on cognitive flexibility tasks. No changes in the results of short-term and working memory tasks were observed in the experimental group, and no changes in any of the measured indices were evident in the controls. In conclusion, 7 weeks of interval running training improved running performance and cycling aerobic power, and were sufficient to improve the ability to adjust behavior to changing demands in young active individuals.

Changes in Indirect Markers of Muscle Damage and Tendons After Daily Drop Jumping Exercise with Rapid Load Increase.

The aim of this study was to assess changes in indirect markers of muscle damage and type I collagen degradation, as well as, patellar and Achilles tendon morphological differences during nine daily drop-jumps sessions with constant load alternated with rapid increases in load to test the hypothesis that frequent drop-jump training results in negative muscular and tendon adaptation. Young men (n = 9) performed daily drop jump workouts with progression every 3 days in terms of number of jumps, platform height and squat amplitude. Voluntary and electrically evoked knee extensor torque, muscle soreness, blood plasma creatine kinase (CK) activity and carboxyterminal cross-linked telopeptide (ICTP), patellar and Achilles tendon thickness and cross-sectional area (CSA) were assessed at different time points during the training period and again on days 1, 3, 10 and 17 after the training. The findings were as follows: (1) steady decline in maximal muscle strength with major recovery within 24 hours after the first six daily training sessions; (2) larger decline in electrically induced muscle torque and prolonged recovery during last three training sessions; (3) increase in patellar and Achilles tendons CSA without change in thickness towards the end of training period; (4) increase in jump height but not in muscle strength after whole training period. Our findings suggest that frequent drop-jump sessions with constant load alternated with rapid increases in load do not induce severe muscle damage or major changes in tendons, nonetheless, this type of loading is not advisable for muscle strength improvement. Key pointsFrequent drop jump training induces activation mode dependent muscle torque depression late in the training period.No significant changes in the thickness of patellar and Achilles tendons are observed during frequent training, while CSA increases towards the end of training period.Longitudinal effect for jump height but not for muscle strength is evident after the whole training period.

Effect of the time of day on central and peripheral fatigue during 2-min maximal voluntary contractions in persons with multiple sclerosis: gender differences.

There is a lack of data on fatigue changes within 24h among patients with multiple sclerosis. The purpose of this study was to evaluate the effect of time of day on central and peripheral fatigue during a continuous 2-min maximal voluntary contraction of the quadriceps muscle in women and men with multiple sclerosis (MS). We studied age-matched MS patients (range, 40-50years). The inclusion criteria for patients were: a Kurtzke Expanded Disability Status score and a Fatigue Severity Scale score. We found a significant gender difference in central activation ratio (CAR) in the evening. At the end of the 2-min maximal voluntary contraction (MVC), the voluntary torque decreased by about 65% in men and women with MS in both the morning and evening. We also observed that, in women, CAR decreased markedly during the first 30s in the evening test. The most interesting finding of our study is that central fatigue increased, whereas peripheral fatigue decreased markedly in the evening only in women. It remains unclear why women's central fatigue is greater in the evening than in the morning.

Repeated bout effect was more expressed in young adult males than in elderly males and boys.

This study investigated possible differences using the same stretch-shortening exercise (SSE) protocol on generally accepted monitoring markers (dependent variables: changes in creatine kinase, muscle soreness, and voluntary and electrically evoked torque) in males across three lifespan stages (childhood versus adulthood versus old age). The protocol consisted of 100 intermittent (30 s interval between jumps) drop jumps to determine the repeated bout effect (RBE) (first and second bouts performed at a 2-week interval). The results showed that indirect symptoms of exercise-induced muscle damage after SSE were more expressed in adult males than in boys and elderly males, suggesting that the muscles of boys and elderly males are more resistant to exercise-induced damage than those of adult males. RBE was more pronounced in adult males than in boys and elderly males, suggesting that the muscles of boys and elderly males are less adaptive to exercise-induced muscle damage than those of adult males.

Reliability and validity of DPA-1 testing after anterior cruciate ligament reconstruction.

There is a lack of equipment and methods for the reliable and valid measurements of human neuromuscular control. To overcome this limitation, an analyzer of dynamic parameters (DPA-1) of human hand and leg movements was constructed by Kaunas University of Technology and "Katra" engineers in collaboration with the Lithuanian Academy of Physical Education. The aim of the study was to determine the reliability and validity of the tests performed on the DPA-1 in healthy and injured subjects after the anterior cruciate ligament (ACL) reconstruction surgery. MATERIAL AND METHODS. The men who had undergone a unilateral ACL reconstruction (n=17, on the average 3.8 months [SD, 2.1] after the surgery) and healthy untrained men (n=17) performed the research protocol twice within 24 hours in between. Average reaction time, mean and maximal movement speed, time to reach maximal speed, and movement distance of the right and left feet for the patients and of the dominant foot for the healthy subjects using the DPA-1 as well as the scores of isokinetic muscle strength and self-assessment tests were registered. RESULTS. There was a significantly reduced concentric peak torque on the injured knee compared with the uninjured knee during knee extension, and the mean score of the Lysholm scale for the injured knee was 69.1 (SD, 13.7) (P<0.05, compared between legs). The test-retest reliability for all the DPA-1 tests varied from 0.68 to 0.94 (P<0.05). However, there were no significant differences in most variables measured by the DPA-1 between injured knee, uninjured knee, and control knee. CONCLUSIONS. The results revealed low validity of the DPA-1 tests for the evaluation of patients following ACL surgery, despite the reliability of these tests varied from moderate to very high.

Arthroscopic coracoid transposition for recurrent shoulder anterior instability: an operative technique.

We report a technique of an arthroscopic concomitant Bankart repair with a transfer of the coracoid bone block and conjoint tendons for revision anterior shoulder instability. The operative procedure consists of an arthroscopic transfer of the conjoined tendon with a coracoid and arthroscopic Bankart repair. First, a typical Bankart suture anchor procedure with two suture anchors was performed into the antero-inferior part of the glenoid rim. After, tenodesis of the coraco-biceps tendon was performed in the middle of the subscapularis tendon fixing the coracoid bony fragment into a glenoid socket with a bioabsorbable interference screw. This operative technique is an alternative in the treatment of revision anterior shoulder instability in patients with deficient anterior capsule.

The effect of multiple sclerosis and gender on central and peripheral fatigue during 2-min MVC.

OBJECTIVE: The aim of this study was to evaluate the effect of secondary progressive MS disease on central and peripheral fatigue in women and men during continuous 2-min maximal voluntary contractions (MVC) of the quadriceps muscle. METHODS: We studied age-matched (40-50-years of age) healthy individuals (men, n=9; women, n=10) and MS patients (men, n=9; women, n=9). The inclusion criteria for MS patients were a Kurtzke Expanded Disability Status Score <4 and a Fatigue Severity Scale Score >5. RESULTS: The electrically-induced torque, MVC, and voluntary activation (VA) values were significantly greater in healthy persons than in MS patients. At the end of exercise, the fatigue index of MVC and VA was greater in MS patients than in the healthy cohort, whereas the electrically-induced torque was significantly decreased in healthy individuals. Peripheral fatigue was directly correlated with VA in MS patients; in contrast, it was inversely correlated with VA in healthy men. The variability of torque increased significantly during exercise and did not depend on MS and gender. CONCLUSIONS: MS increased central fatigue and diminished peripheral fatigue significantly during 2-min MVC; however, only peripheral fatigue was significantly greater in healthy men than in healthy women. SIGNIFICANCE: These results suggest the specified pattern of central and peripheral fatigue in MS patients and could be further exploited for potential therapeutic uses, for instance, to model exercise-induced less central fatigue, and this may not be differentiated between men and women.

Leg immersion in warm water, stretch-shortening exercise, and exercise-induced muscle damage.

CONTEXT: Whether muscle warming protects against exercise-induced muscle damage is unknown. OBJECTIVE: To determine the effect of leg immersion in warm water before stretch-shortening exercise on the time course of indirect markers of exercise-induced muscle damage. DESIGN: Crossover trial. SETTING: Human kinetics laboratory. PATIENTS OR OTHER PARTICIPANTS: Eleven healthy, untrained men (age = 21.5 +/- 1.7 years). INTERVENTION(S): Participants' legs were immersed in a water bath at 44 +/- 1 degrees C for 45 minutes. MAIN OUTCOME MEASURE(S): Creatine kinase changes in the blood, muscle soreness, prolonged (within 72 hours) impairment in maximal voluntary contraction force and height of drop jump, and electrically evoked muscle force at low and high stimulation frequencies at short and long muscle lengths. RESULTS: Leg immersion in warm water before stretch-shortening exercise reduced most of the indirect markers of exercise-induced muscle damage, including creatine kinase activity in the blood, muscle soreness, maximal voluntary contraction force, and jump height. The values for maximal voluntary contraction force and jump height, however, were higher during prewarming than for the control condition at 48 hours after stretch-shortening exercise, but this difference was only minor at other time points. Muscle prewarming did not bring about any changes in the dynamics of low-frequency fatigue, registered at either short or long muscle length, within 72 hours of stretch-shortening exercise. CONCLUSIONS: Leg immersion in warm water before stretch-shortening exercise reduced most of the indirect markers of exercise-induced muscle damage. However, the clinical application of muscle prewarming may be limited, because decreasing muscle damage did not necessarily lead to improved voluntary performance.

Children are more susceptible to central fatigue than adults.

Performance in high-intensity exercise is dependent on the ability to activate motor units. The main aim of this study was to test the hypothesis that adult men and women (age 19-27 years) are able to maintain higher levels of voluntary activation (VA) in knee extensor muscles than boys and girls (age 12-14 years). The volunteers (n = 7 in each group) performed three 5-s maximal voluntary contractions (MVCs) and a continuous 2-min MVC. The VA and fatigue of the muscles was assessed by applying 250-ms 100-HZ test tetani (TT100HZ). During brief MVCs girls showed lower VA than women, but the difference between boys and men was not significant. During the 2-min MVC, VA in boys and girls was more depressed than in adults. The end-exercise values of the relative TT100HZ torque correlated with the average VA during the exercise. Thus, the results of the study support the hypothesis that children are more susceptible to central fatigue than adults. This should be taken into account when evaluating results of fitness tests that require high levels of motor unit activation.

[Impact of intensive and traditional rehabilitation on quadriceps strength after anterior cruciate ligament reconstructive surgery]. / Intensyviosios ir iprastines reabilitacijos poveikis blauzdos tiesiamuju raumenu jegai atlikus priekinio kryzminio raiscio rekonstruojamaja operacija.

UNLABELLED: After knee anterior cruciate ligament reconstructive surgery, the recovery of the former level of physical activity takes from 3 to 12 months. Such a wide range of recovery period of physical activity suggests that rehabilitation in most cases is not optimal. According to the majority of authors, after the surgery, a patient can resume intensive physical activity, when the difference in muscle strength between the operated lower extremity and another extremity is not greater than 10-15%. The aim of this study was to compare the impact of intensive and normal rehabilitations on the recovery of knee extensor muscle strength after the surgery. MATERIAL AND METHODS: A total of 40 patients were enrolled in this study. The subjects were divided into two groups. Both groups were engaged in physical activity. The mean age of patients (16 men and 4 women) in the first group at the time of surgery was 26.4+/-8.1 years, mean height - 179.8+/-8.5 cm, and mean weight - 76.0+/-14.0 kg. An intensive rehabilitation was applied for the first group of the patients studied. The second group consisted of 13 men and 7 women who were engaged in moderate physical activity. Their mean age at the time of surgery was 27.0+/-9.3 years, mean height - 173.2+/-6.2 cm, and mean weight - 71.0+/-9.0 kg. A traditional rehabilitation was applied to this group. Muscle strength was measured in the patients of both groups studied approximately 5.2 months following surgery using the Biodex isokinetic dynamometer. RESULTS: The patients undergoing an intensive rehabilitation achieved higher levels of knee extensor muscle strength than those patients undergoing a traditional rehabilitation program. Applying an aggressive rehabilitation program, knee extensor muscles recover more quickly than using a traditional rehabilitation program. The comparison of intensive and traditional rehabilitation programs applied to the operated and unoperated lower extremities has shown that the indexes of knee extensor muscle strength differed by 11.51-12.74%. Applying a traditional rehabilitation, a 23.68-49.42% difference in knee flexor muscle strength between operated and unoperated extremities was noted. CONCLUSIONS: The effect of intensive rehabilitation aimed at strength recovery of knee extensor muscles after anterior cruciate ligament reconstructive surgery is greater than after ordinary rehabilitation.

The Time-Course of Voluntary and Electrically Evoked Muscle Performance During and After Stretch-Shortening Exercise is Different.

The aim of the study was to establish the dynamics of maximal voluntary contraction force (MVCF), height of drop jump (DJ) and electrically evoked quadriceps muscle force at different stimulation frequencies during and after 100 DJs (stretch-shortening exercise, SSE). Healthy untrained men (n = 11; age = 21.8 ± 1.7 years) participated in the study. DJs were performed with 30 s intervals between jumps from the height of 0.5 m with counter-movement to 90 degrees angle in the knee and immediate maximal rebound. The force of the quadriceps muscle, evoked by electrical stimulation at 1 Hz (Pt), 20 Hz (P20) and 100 Hz (P100) frequencies (electrically evoked performance, EEP), MVCF and height of DJ (voluntary evoked performance, VEP) were established during SSE (after 10, 50, 100 DJ) as well as at 1, 4, 8, 24, 48 and 72 h after SSE. Time-course of P20 and P100 during and after SSE was time (ANOVA: p < 0.001) and frequency dependent (ANOVA: p < 0.001) The Pt, P20 and P100 decreased significantly (p < 0.01) more than MVCF and H of DJ during SSE. At the beginning of SSE (during 1-10 DJs) P20 and P100 decreased significantly (p < 0.001) more than during 11-50 and 51-100 DJs. There was a significant (p < 0.05) increase in Pt, P20 and P100 from 8 h to 48 h, whereas height of DJ and MVCF significantly decreased at that time. In conclusion, the differences in time course of VEP and EEP are most evident at beginning of SSE, where VEP does not change as EEP decreases, and within 8-48 hours after SSE, where VEP decreases as EEP increases. Key pointsThere was no change in voluntary muscle performance while electrically evoked performance decreased significantly during first 10 drop jumps.There was a significant increase in electrically evoked muscle performance from 8 h to 48 h after 100 drop jumps, whereas voluntary contraction force, decreased significantly.The secondary decrease in the height of drop jump as well as in maximal voluntary contraction force correlated significantly with muscle soreness within 24-48 h after exercise.