Isokinetics and Exercise Science

Few studies have reported contribution of isometric specific training of abdominal muscles to low back and pelvic stability using a modified crook-lying (C-L) posture with and without a labile surface.

To investigate activation amplitude of rectus abdominis (RA), external oblique (EO), and internal oblique (IO) in C-L posture based on various foot and trunk supporting surfaces.

Participants were 32 healthy adults. Abdominal muscles activities were measured using surface electromyography while performing an exercise with a straight one-leg hold in C-L posture with four different exercise conditions. Two-way repeated measures analysis of variance (ANOVA) with Bonferroni’s correction was used to determine effects of exercise tasks of different conditions on the activation of RA, EO, and IO.

Significant differences in abdominal muscle activities were found between supporting surface conditions for all muscles ( p < 0.05). RA showed significantly higher muscle activity on more unstable supporting conditions ( p < 0.05). EO and IO showed significantly higher muscle activities on trunk support and trunk plus foot support conditions than those with other conditions ( p < 0.05). However, there were no significant differences in muscle activities between trunk support and trunk plus foot support conditions in C-L posture ( p > 0.05).

Application of unstable trunk and foot support surface while performing straight one-leg hold exercise in C-L posture could be useful for improving the endurance and strength of each abdominal muscle.

Shooting accuracy and ball speed are important factors relating to scoring in handball that could be affected by skeletal muscle fatigue.

To explore the effects of muscle fatigue on male handball players’ shooting accuracy and ball speed.

Sixteen elite handball players ( M age = 17.1 ± 1.7 years) participated in the laboratory and the field-testing sessions. Running speeds equal to 75% of participants’ maximal oxygen uptake (VO2max) values from laboratory tests were used as the initial velocity for the 30–15 intermittent fitness test (30–15 IFT ) in the fatigue protocol. Participants shot to the target at random visual signals placed behind the target before and after fatigue. In order to measure wrist acceleration and ball speed, an accelerometer and a radar gun are used respectively and numbers of accurate and inaccurate shots also recorded.

There were no significant differences between pre-fatigue and post-fatigue protocols in terms of accurate and inaccurate shots, and ball speed. Only wrist acceleration in the Y axis ( M pre - fatigue = 33.12, SD = 1.17msec; M post - fatigue = 34.50, SD = 1.21msec) was affected by the fatigue protocol in inaccurate shots ( p = 0.042).

Muscular fatigue does not affect shooting accuracy and ball speed in male handball players.

The ability to train unilaterally and experience contralateral strength gains, a phenomenon known as cross-education, has been well documented in the lower extremity but not the upper. Additionally, short-term training of one to two weeks has shown neural adaptations in strength.

To examine the effects of a short-term cross-education strength-training program on contralateral shoulder strength.

Twenty-seven healthy college students (age: 21.37 ± 2.02 years; height: 167.85 ± 7.63 cm; mass: 74.42 ± 16.73 kg) were randomly assigned to either an experimental ( n = 13) or control group ( n = 14). All participants completed a pre and post-test separated by two weeks. Testing consisted of 6 maximal repetitions of shoulder internal/external rotation, at each of three speeds (60 and 180 ∘ /s). The experimental group underwent right arm unilateral training (3 × 10 repetitions at all 3 speeds) two times a week for the next two weeks on the same dynamometer. Control group did not train.

A 2 × 2 × 2 × 2 (time × arm × speed × group) ANOVA revealed no significant interactions by group, however there main effects of time and arm. For internal rotation, peak moment was significantly greater in the right arm and at 60 ∘ /s, and average power was significantly greater in the right arm and at 180 ∘ /s. For external rotation; peak moment, average power and total work, were significantly greater in the right arm and at 60 ∘ /s.

Short-term cross education training showed no increase in contralateral shoulder strength. Therefore, short-term cross education strength training should not be considered a useful tool in shoulder rehabilitation at this time. However, future research should investigate contrasting training programs.

Effects of whole-body-vibration (WBV) training have been claimed to depend on individual characteristics and vibration frequency; however, there have not been any studies focusing on effects of different WBV frequencies on flexibility, jump performance, and dynamic balance ability in the same group.

Twenty healthy men participants were randomly assigned to three conditions [0 Hz, 25 Hz, 40 Hz] prior to the study. They stood barefoot on the non-dominant leg and performed WBV of 5 sets × 30 seconds. In pre- and post-WBV in each condition, the participants measured ankle dorsiflexion angle; single leg squat jump (SLSJ) height; and dynamic postural stability index (DPSI), anterior-posterior stability index (APSI), medial-lateral stability index (MLSI), and vertical stability index (VSI).

Ankle dorsiflexion angle at 25 and 40 Hz and SLSJ height at 25 Hz significantly increased after WBV ( p < 0.01). DPSI and APSI at 25 Hz and 40 Hz significantly decreased, except VSI, which was significant only at 25 Hz ( p < 0.05).

The acute effects of exposure to WBV on flexibility, jump performance, and dynamic balance ability differ by the selected vibration frequencies.

Basketball players playing for the University of Hawai’i Hilo are subjected to well above normal physiological and psychogenic stressors with their exposure to significant amounts of easterly-bound air travel that include time zone and seasonal changes throughout one season.

The aim of this study was to investigate the effects of a basketball season on physiological, anthropometrical, biometric markers, strength and power of men’s collegiate basketball team who play their away matches after a relatively long (up to 6 h) eastward flight.

Thirty-six men collegiate basketball players and a control group of thirty-seven university students, were included in this study. Measurements were commenced at the beginning of the season and concluded immediately post-season.

Post-season, players presented with significant gains for resting levels of salivary cortisol; significant gains in visceral trunk fat, total body fat percent or body weight, in resting heart rate and mean arterial blood pressure; and diminishment in leg muscle isokinetic force, most noticeably in knee flexion strength. Vertical jump height also decreased significantly post-season. These changes were not found in the control group.

A flight-travel-heavy basketball season resulted in broad-spectrum declinations in variables related to overall health and well-being in men collegiate basketball players. It is concluded that the prolonged intermittent stress of such a season resulted in measureable stress such as increased cortisol levels, increased blood pressure and heart rate, and selective increase in visceral trunk fat, total percent body fat thus total body weight.

Some disabled persons especially those with Down syndrome have cardiorespiratory disorders that negatively influence their daily life. Strength training for respiratory muscles may positively affect daily life of such disabled persons.

The purpose of the study was to investigate the effects of inspiratory muscle training on respiratory functions and respiratory muscle strength in individuals with Down syndrome.

Sixteen individuals were enrolled and divided into experimental ( n = 9) and control ( n = 7) groups. The experimental (40% of maximal inspiratory pressure) and control (0% of maximal inspiratory pressure) groups were trained 5 days per week for 4 weeks with an inspiratory muscle training device. In both groups, respiratory functions (slow vital capacity and forced vital capacity) and respiratory muscle strength (maximal inspiratory pressure and maximal expiratory pressure) were measured one day before and after the 4-week training period.

Significant pre-post changes were found in the respiratory functions and respiratory muscle strength of the experimental group ( p < 0.05) while no took place in the control group ( p > 0.05). All the measurements, including maximal inspiratory pressure, maximal expiratory pressure (as respiratory muscle strength), forced vital capacity, forced expiratory volume in one second, forced vital capacity to expiratory volume ratio (FEV1/FVC), peak expiratory flow, peak inspiratory flow, maximal voluntary ventilation, vital capacity, and inspiratory vital capacity increased significantly.

Inspiratory muscle training is likely to have a positive effect on respiratory functions and respiratory muscle strength in individuals with Down syndrome.

Warm up exercises are common practice before training and competition in almost every sport. Although, swimming is a popular sport throughout the world, studies on the effects of warm-up are scarce.

The purpose of this study is to compare the effects of different stretching warm-up and exercise protocols on swim performance.

Fourteen sub-elite college women swimmers volunteered to participate in the study. The four stretching and warm-up protocols they followed were; (I) without stretching (WS); (II) static stretch (SS); (III) in-water (IW); and (IV) dry land (DL).

There was a significant main effect for 50-meter front crawl (F = 70,453; p = 0.00) and breaststroke swimming performances (F = 145.504; p = 0.000). The best 50-meter front crawl and breaststroke performance detected immediately after IW was 28.1 and next, 39.9 seconds. Pairwise comparison indicated that the best 50-meter front crawl performance monitored after IW protocol was 28.0 ± 2.9 ( p = 0.000) compared with that after WS – 29.8 ± 2.3 ( p = 0.000) and after SS – 30.7 ± 2.2 ( p = 0.000).

Pre-event low-intensity IW warm-ups may be optimal for 50-meter front crawl and breaststroke swimming performance.

Extensive research has been conducted related to muscle fatigue, but little attention has been given to shoulder rotator muscles. Many different formulas have been used to calculate fatigue. Therefore, there is a need for establishing a reliable fatigue assessment protocol to further assess shoulder rotators using a suitable fatigue formula.

To study the reproducibility of two different isokinetic set-ups for assessing shoulder rotators fatigability properties and explore a possible clinical implication when different fatigue calculation formulas are used.

Forty sedentary subjects took part in this study. They were randomly assigned to either the “45 ∘ group” or the “90 ∘ group”, where the upper limb was either abducted to an angle of 45 ∘ or 90 ∘ in the frontal plane, respectively. All participants completed two testing sessions, consisting of 30 maximal concentric contractions on dominant shoulder IR and ER muscles at 180 ∘ /s. Relative reproducibility, absolute reproducibility and fatigue indices were assessed.

ER was different ( p < 0.05) between trials (5%). Relative reproducibility was high for both muscles (ICC 0.97–0.99). Absolute reproducibility remained homogeneous with a SEM of 4–6% while the MDC varied between 11% and 16%. Fatigue formulas estimated no difference between trials (0–2%) for any muscle groups.

Based on this study of reproducibility, both abduction set-ups may be used for assessing fatigue performance without indicating a superiority for either.

An enthusiasm for physical exercise is often developed in the paediatric age group through collective game-based sporting activities. Regular exercise via sports can create positive effects on the respiratory systems of boys as well as on their overall growth and development. To help identify deviations from positive trends in these areas, respiratory function tests have become an essential part of the diagnosis and assessment of pulmonary disease.

To investigate the effect of different types of sports on pulmonary functions and respiratory muscle strength and to help establish baseline reference values in healthy Turkish boys aged 8–12 years.

A total of 624 healthy boys, who train at least twice a week for football (128), basketball (105), archery (60), swimming (111) and wrestling (74), as well as 146 boys who do not perform regular physical activities voluntarily, participated in the study. To evaluate and potentially differentiate amongst the merits of these several sports, we obtained a variety of baseline measurements from our subjects, including forced vital capacity (FVC), forced expiratory volume in one second (FEV1), FEV1/FVC, maximal peak expiratory flow (PEF max), maximal voluntary ventilation (MVV), maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP).

There were statistically significant differences amongst the types of sports regarding the various metrics we examined: FVC, FEV1, FEV1/FVC, PEF max, MVV, MIP and MEP ( p < 0.05). The active boys showed higher mean values for pulmonary functions and respiratory muscle strength than the passive ones. Also, the wrestlers generally had better respiratory parameters than those of athletes in the other four sports we investigated.

It was clear that exercise, especially regarding pulmonary function and respiratory muscle strength, produced better outcomes in the active boys compared with our control group of relatively passive boys. The mechanisms responsible for this difference are likely due to the resistance effect of exercise.

In recent years, power assist suits have been used in nursing and rehabilitation scenarios. The external assistive force might disturb the user’s motor control system during the process of assisted training using power assist suit, thus affect the progress of rehabilitation. With the consideration of the non-negligible physiological differences between upper limbs, this study focused on the physiological responses of the two arms against the external assistive force.

To investigate and contrast the impact of assistive force on dominant and non-dominant arms during unilateral isometric elbow flexion.

Participants were instructed to adjust force exertion to a target value based on the visual feedback. Task performances including muscle activity of agonist and antagonist muscles, force steadiness and rated perceived exertion were evaluated at multiple workload and assistive load conditions.

No significant differences in muscle activity of agonist and antagonist muscles between the two arms. In contrast, the dominant arm showed a higher assist efficiency at a low assistive level, whereas the non-dominant arm had a lower level of force fluctuation during a unilateral force matching task.

Both arms could utilize the assistive force to reduce muscle activity. However, the two arms showed different abilities in response to external assistive force. This indicates distinct motor control strategies for each arm and implicates the necessity of side-individualized rehabilitative approach for achieving a better training effect.

In countries where water polo is a minority sport, coaches often recruit young players to senior teams.

To explore whether young water polo players are ready to train and play with older players from a physical and strength perspective.

Forty-four adolescent and senior water polo players (20 women and 24 men) were evaluated on full anthropometry, absolute and relative isokinetic muscle strength of shoulder internal and external rotator muscles (60 and 240 ∘ /s) and hand grip strength.

The strength of the internal rotators was significantly greater than that of the external rotators in both sexes and age groups. Senior male players had significantly higher values for variables related to body size and absolute strength in these muscle groups compared to their adolescent counterparts but these differences were not observed among women.

Adolescent female players but not male players may be physically prepared to compete and train with senior teams.

The circadian rhythm (CR) is a 24-hour cyclic period that influences a wide array of physiological systems and performance sports. However, its specific effect on drop jump (DJ) scores have not been studied.

To investigate the effect of circadian rhythm on DJ performances.

Thirty-three healthy university students (men, n = 16, age: 23.47 ± 2.9 years; fewomen, n = 17, age: 22.25 ± 2.27 years) participated in this study. Subjects were tested twice, over two separate days, once in the morning and once in the evening. Subjects started from a drop height of 20 cm and continued until the height where the reactive strength index (RSI) started to decrease. This height was recorded as the optimal drop height (ODH). Ground contact time (GCT) and jump height were also recorded.

The ODH values were similar between testing sessions for both genders ( p > 0.05). A significant increase in jump height during the evening session was observed in men ( p = 0.005, d = 0.80). The RSI values increased significantly in men ( p = 0.006, η 2 = 0.77) while GCT was similar in both genders ( p > 0.05).

In men, the optimal time of day for DJ explosive training is the evening. Women may benefit from this type of training both during morning and evening sessions.