Isokinetics and Exercise Science

Postactivation potentiation (PAP) is an acute and temporary enhancement of muscular performance resulting from previous muscular contraction. Extensive research exists examining the PAP effect after a heavy resistance exercise but there is limited research examining the PAP effect after a plyometric stimulus to the pre-competition practices (e.g., warm-up) of well-trained athletes.

The purpose of this study was to investigate the acute effects of plyometric warm-up with different box heights on sprint and agility performance in national-level field hockey athletes at recovery time of immediately, 5 minutes and 10 minutes.

In a randomized crossover design, ten male national-level field hockey athletes performed 30-m sprint (with 10-m split) and agility test at baseline, immediately ( ∼ 15 sec), 5 minutes and 10 minutes after a high-intensity plyometric warm-up (HIPW), a low-intensity plyometric warm-up (LIPW) and a control trial (CT).

Mean 10-m sprint times, 30-m sprint times and agility times were similar between trials at baseline ( p > 0.05). Significant trial x time interactions ( p ⩽ 0.05) were observed for 10-m sprint time, 30-m sprint time and agility time. 10-m sprint times were significantly decreased after HIPW at all time-points and LIPW at immediately time-point, relative to baseline ( p ⩽ 0.05). HIPW 10-m sprint times were faster at all time-points and LIPW sprint time was faster at 10 minutes when compared with CT ( p ⩽ 0.05). Thirty-meter sprint times were significantly decreased after HIPW and LIPW at all time-points, relative to baseline ( p ⩽ 0.05). HIPW 30-m sprint times at all time-points and LIPW at both the 5 and 10 minute time-points were faster than CT ( p ⩽ 0.05). Agility times were significantly decreased after HIPW at all time-points and LIPW at both the immediately and 5 minutes time-points, relative to baseline ( p ⩽ 0.05). HIPW and LIPW agility times were faster than CT, at all time-points ( p ⩽ 0.05).

Both HIPW and LIPW may be effective in enhancing the pre-training or pre-competition practices in off-season for national-level field hockey athletes. However, the individualization of HIPW is highly recommended in order to maintain PAP effects for 10-m sprint times, 30-m sprint times and agility times throughout the 10 minutes when compared to LIPW.

Traditional and rest-pause systems are commonly used during resistance training. These systems have different rest times between repetitions that might affect neuromuscular status and fatigue level.

This study compared the acute effects of traditional and rest-pause resistance exercise done to muscular failure on countermovement jump (CMJ) performance.

Twenty-nine recreationally strength-trained adults of both sexes aged from 18 to 33 years old performed four experimental resistance exercise sessions (half back-squat exercise) in a randomized order. The experimental conditions were: Traditional system to muscular failure (TR-F; 4 × 15 [15RM]) or non-failure (TR-NF; 5 × 12 [15RM]), and rest-pause system to muscular failure (RP-F; 60 reps with 30 s rest between each failure) or non-failure (RP-NF; 60 reps with 10.2 s rest between each repetition). CMJ height was measured at pre-experiment, Post-15 s, and Post-30 min. Perceived recovery was assessed at pre-experiment, lactate concentration Post-2 min, and rating of perceived exertion Post-30 min.

CMJ height decrease occurred at Post-15 s and 30 min for the TR-F, TR-NF, and RP-F sessions ( p < 0.05). Interaction effects ( p < 0.05) showed exercise to muscle failure (TR-F and RP-F) induced greater neuromuscular decrement at Post-15 s, with RP-F leading to a higher CMJ performance impairment at Post-30 min ( p < 0.001). Higher blood lactate concentrations were found following TR-F, TR-NF, and RP-F ( p < 0.05) than RP-NF conditions, whereas greater internal training load perception was reported after training to muscular failure ( p < 0.05) than non-failure exercise.

Resistance exercise to muscular failure induced greater CMJ height decrement and internal training load perception than non-failure exercise, with RP-F leading to a higher acute neuromuscular performance impairment.

The scapular dyskinesis has been described as a sign of scapular instability due to weakness or imbalance of scapular muscles.

The aim of this study was to compare the EMG activity of the periscapular and abdominal muscles of asymptomatic subjects without and with scapular dyskinesis type II during a push-up exercise performed on different surface stability conditions.

Twenty-seven physically active men were allocated into two groups: the Control group ( n = 14); and the Dyskinesis group ( n = 13). All participants performed three variations of the push-up exercise: Stable, Push-up with hand instability, and Push-up with hand and feet instability. The EMG activity of serratus anterior, upper (UT), middle (MT) and lower (LT) trapezius, external oblique (EO) and rectus abdominis (RA) was recorded during each task.

The control group showed an increase in MT activity (mean difference - 3.46 to 8.66) under both instability conditions compared to stable push-ups ( p < 0.001). The comparison between groups showed that the control group had higher MT activity (mean difference - 10.07 to 13.82) compared to the dyskinesis group under unstable conditions ( p < 0.012).

The insertion of unstable surfaces increased MT activity in the control group only. The insertion of the unstable surface, either the hands or the footrest, did not provide significant effects for the other muscles.

The effects of abdominal exercises on the inter-rectus distance are unclear.

To compare the inter-rectus distance at rest and during different abdominal exercises: abdominal crunch, abdominal crunch with transversus abdominis pre-activation and hypopressive exercise.

A transversal experimental study was carried out in 98 healthy adults without diastasis recti abdominis were recruited. Measurements were assessed using ultrasound imaging, and two points were evaluated: just above the umbilicus (U point) and halfway between the U point and the xiphoid (UX point). The inter-rectus distance was measured at rest and during the abdominal exercises.

The abdominal crunch with transversus abdominis pre-activation increases the inter-rectus distance in comparison with rest and with abdominal crunch in the U point.

These results increase the knowledge about the behaviour of the linea alba and inter-rectus distance during abdominal exercises, with practical applications in the rehabilitation of the abdominal wall and low back.

Blood flow restriction (BFR) resistance training (RT) has garnered recent interest, but female-specific data remains scarce.

The purpose was to examine the effects of 2-wks of low-load concentric, isokinetic, reciprocal forearm flexion and extension training, with and without BFR on perceptual responses, performance fatigability, and muscular strength.

Twenty women were assigned to a BFRT or a non-BFRT group. Each group trained at 30% of concentric peak moment. Each session consisted of 75 concentric, isokinetic, reciprocal forearm flexion extension muscle actions. RPEs were recorded following each set. Pretest and posttest maximal voluntary isometric contraction (MVIC) force was measured, and percent decline was defined as performance fatigability.

The RPE values ( p < 0.05) increased across sets. Strength (collapsed across muscle action) increased ( p < 0.05) from 0-wk (23.7 ± 3.2 Nm) to 2-wk (26.8 ± 2.7 Nm). Independent of group and muscle action, performance fatigability ( p < 0.05) increased from 0-wk (10.9 ± 5.0%) to 2-wk (14.1 ± 4.4%).

2-wks of low-load concentric, reciprocal forearm flexion and extension training resulted in similar training-induced changes in perceptual responses, performance fatigability, and muscular strength between BFRT and non-BFRT. These findings may reduce concerns of increased perceptual responses following BFRRT compared to non-BFRRT.

Aging-related deterioration of the lower limb muscle strength could highly influence the functional performance of elderly individuals.

To investigate how advancing age impacts the lower limb muscle strength and consequently affects the balance and walking performance.

Twenty-seven community-dwelling elderly females underwent isokinetic ankle dorsi/plantar flexion (ADF/APF), inversion/eversion (AIN/AEV), knee flexion/extension (KFL/KEX), hip flexion/extension (HFL/HEX), and abduction/adduction (HAB/HAD) tests, the six-minute walk test, open-eyed biped balance test on foam rubber and the performance-oriented mobility assessment (POMA).

The Pearson’s product-moment correlation coefficients demonstrated that advancing age negatively influenced the relative work and moment produced in all the muscle groups, the POMA score ( r = - 0.51), walking speed ( r = - 0.62), and the vertical ( r = 0.55) and anteroposterior ( r = 0.54) postural sway velocities. The peak moment and work values of AINs and APFs; KFLs and KEXs; and HABs, HFLs, and HEXs showed a significantly positive correlation with the walking speed ( α ⩽ 0.05).

The strength of HFLs, HEXs and HABs, as the important contributors to the walking performance, underwent attenuation as the age increased, consequently resulting in impairments of stepping profiles of elderly females. Elderly females are needed to be trained to reach the optimum levels of lower limb muscular strength to overcome premature incapacitation and have control over their independence in daily activities.

Few studies have examined sex differences in performance fatigability and the bilateral deficit in a dynamic modality.

The purpose of this study was to examine: 1) Leg-, mode-, and sex-specific differences in performance fatigability during maximal, dynamic leg extension muscle actions and; 2) the time course of fatigue-induced changes in the bilateral deficit for both men and women.

Eleven men and 11 women participated in 3 test visits consisting of 50 maximal, concentric, isokinetic leg extensions at 60 ∘ /s. Each visit was randomized to perform either unilateral right leg only (RL), unilateral left leg only (LL), or bilateral (BL) leg extensions.

The BL performance fatigability was significantly ( p < 0.001) less than RL and LL. Both men and women demonstrated significant ( p < 0.001) declines in moment and an attenuation of the bilateral deficit throughout the fatiguing task. There were no differences between sex for performance fatigability ( p = 0.128) or the bilateral deficit ( p = 0.102).

Unilateral muscle actions were more susceptible to fatigue than BL muscle actions. Men exhibited an earlier decline in moment than women, however, men and women exhibited similar magnitudes and patterns of decline in the bilateral deficit.

Life expectancy among older adults has dramatically increased and they are one of the fastest growing populations worldwide. Maintaining quality of life and the ability to live independently are often of greater importance than overall life expectancy.

To present reference values for tests of muscle function, and to study the relationship to a commonly used tool of generic health related quality of life (HRQL) in older Swedish adults.

The study consisted of 192 individuals (105 women) aged between 65 and 80. The tests included hand grip and isometric knee extension strength measurements, the standing heel rise test and a 30 m walking test. Health-related quality of life (HRQOL) was evaluated using the SF-36.

Reference values for the measured parameters are presented. There were high correlations ( n = 192) between handgrip and leg extension strength ( r = 0.72–0.75; p < 0.01). The walking test’s self-selected speed demonstrated the strongest correlation with the physical component summary of the SF-36 ( r = 0.57; p < 0.01) and with maximal speed, moderate correlations were demonstrated with muscle strength ( r = 0.43–0.56; p < 0.01) and the heel rise test ( r = 0.45; p < 0.01).

This study presents reference values for simple tests of muscle function which are relatively easy to perform, used in a Swedish clinical setting performing screening for older adults.

Scoliosis affects mainly women and even if its diagnosis relies on clinical evaluation and radiographic assessment, muscular involvement is undeniable impacting possibly on strength and daily activities.

To assess the strength of sagitally operating trunk muscles in women with scoliosis (WwS) and apparently healthy women (AH) with a similar mean age.

The two groups consisted 114 WwS and 42 AH women. The concentric isokinetic evaluation related to the peak moment (PM) of the trunk flexors and extensors at 30 and 90 ∘ /s. Division into subgroups was based on the location of the scoliosis and magnitude of the Cobb angle.

The PM of both muscle groups was not correlated with the location of the scoliosis. However, these muscles manifested a highly significant weakness in WwS compared to the AH group, in both test velocities. In terms of the general severity of the weakness, the PM scores in WwS with Cobb angle > 30 ∘ were significantly lower compared to their healthy counterparts in both ‘muscle’ and ‘velocity’ whereas save the flexors at 90 ∘ /s, there was no difference between the lesser compromised WwS (Cobb ⩽ 30 ∘ ) and AH women. The PM-based extension/flexion ratios in WwS were respectively 1.34 ± 0.28 and 1.23 ± 0.27 at 30 ∘ /s and 90 ∘ /s, with no significant difference between subgroups, nor with control values.

In view of the results, trunk muscles strength should definitely be taken into account when planning therapeutic options for WwS.

Volleyball player’s performance depends on a combination of technical-tactical skills and an optimum level of general and specific physical fitness.

The purpose of the study was to compare the results of three isometric strength tests with the results of four specific volleyball performance tests using a novel Multidimensional Modelling Approach.

In a cross-sectional study 80 male (age = 16.2 ± 1.7 yrs.) and 116 female (age = 16.1 ± 1.5 yrs.) volleyball players performed two testing sessions consisting of ankle extensor, handgrip, and lumbar isometric strength tests, followed by countermovement tests, modified X test and medicine ball throw.

Principal Component Analysis, with 51.38% to 64.87% of variances explained, was used to group results from multiple tests into a single score: isometric force (F max Score), rate of force development (RFD max Score), and specific performance tests (Specific Score). Calculated F max Score, and RFD max Score values showed low ( r = 0.310–0.416), but statistically significant ( p < 0.01) correlations with Specific Score. Regression analysis showed 17.3% and 9.6% influence of F max and 16.9% and 10.1% influence of RFD max on specific abilities for male and female sample respectively.

The findings derived from the isometric strength tests are not related to those obtained from specific volleyball performance tests. However, the advantages of isometric tests and their findings may be of a comparative clinical value in management of sports injury in volleyball players.

Cycling has been the subject of numerous studies. Among these, measuring muscular performance during cycling has attracted much interest.

To investigate the relationship between Wattbike ® and isokinetic findings in a group of cyclists.

Thirty-seven male cyclists performed a 30-s anaerobic power test on a Wattbike ® and then were tested concentrically for knee extensor and flexor strength using isokinetic dynamometry.

There was a positive fair-to-moderate correlation between the peak moment, peak power, and total work derived from the Wattbike ® and the respective parameters evaluated isokinetically.

While the findings exclude interchangeability of the two methods, the fact that total work is the most closely associated parameter among the measurements highlights its importance as an outcome measure in muscle performance in cyclists.

Small-sided games are a popular training method that have shown its effectiveness in improving athletic performance in football players.

To compare the acute physiological and neuromuscular responses and time-motion characteristics during small-sided games played with and without wildcard players.

Sixteen amateur male football players completed two small-sided games protocol: 4-a-side and 4-a-side with wildcard players. Time-motion characteristics during games, muscular performance parameters before and after small-sided games protocols, physiological response in terms of heart rate and muscle oximetry and rate of perceived exertion were collected.

Both small-sided games formats induced changes in sprint performance (before-after comparison), in the rate of perceived exertion, heart rate-related variables and time-motion parameters ( p < 0.05). In a comparison between small-sided games formats, lower values of oxygen saturation, heart rate, rate of perceived exertion and time-motion parameters ( p < 0.05) were reported during small-sided games with wildcard players in both working and recovery periods.

The inclusion of wildcard players during small-sided games cause a reduction in perceptual, physiological demands and time-motion parameters when compared to control condition.