Isokinetics and Exercise Science

Simple field tests are often used to assess functional mobility in clinical settings. Despite having many benefits, these tests are susceptible to measurement error and individual variation.

To examine the test-retest and absolute reliability of timed up and go test (TUG), five times sit-to-stand (FTSTS), stair climb test (SCT) and 6 minute walk (6MWT).

Over two sessions, thirty-five subjects (30-74 years), repeated the five tests approximately four weeks apart. Test-retest reliability (intraclass correlations [ICC]) and absolute reliability (95% limit of agreements [95% LOA]; standard error of measurement [SEM] and minimum detectable change [MDC]) were calculated.

All five tests had high test-retest reliability (ICC > 0.95) although significant between session changes were present for the TUG and FTSTS (p < 0.05). FTSTS displayed the greatest measurement error whilst 95% LOA was the most conservative measure of absolute reliability.

The results of this study indicate that the TUG, FTSTS, SCT and 6MWT are reliable when performed four weeks apart. Furthermore, the inclusion of SEM, MDC and 95% LOA provides reference values to aid in identifying changes over time above those of measurement error and individual variation.

Gender-based delta blood lactate concentration (Δ [BLa ^- ]) differences may be impacted by the volume of work performed during exercise. Thus workload can act as a confounding influence when data from men and women are compared.

To examine workload's impact on gender-based disparities in delta blood lactate concentration (Δ [BLa ^- ]) values from supramaximal exercise.

Subjects (49 women, 31 men) did two workouts on an exercise device (Impulse Technologies; Newnan, GA) comprised solely of either tonic or phasic repetitions. Total work (TW) and Δ [BLa ^-] were quantified from each workout. TW and raw Δ [BLa ^- ] values were each examined with 2 × 2 ANOVAs, with repeated measures for workout. Δ [BLa ^- ] values were also examined with TW as a covariate using a 2 × 2 ANCOVA and repeated measures for workout.

Raw Δ [BLa ^- ] and TW results each yielded predictable inter-gender differences. However our ANCOVA data produced a two-way interaction and the following significant differences: men-phasic, women-phasic > women-tonic > men-tonic.

Our results support the idea that the volume of TW performed exacerbates inherent metabolic differences among men and women that heighten gender-based blood lactate differences. Future research on inter-gender lactate differences should consider workload as a covariate.

The prone bridge is one of core stability exercises, which is important to maintain pelvic position as neutral. Elevated feet position is simple way to increase the external load, but have not been investigated the effect for muscle activity and pelvic position.

Present study is to investigate the effect of feet height on muscle activity and pelvic tilt angle during the prone bridge exercise.

Surface electromyographic responses of the rectus abdominis, internal oblique, erector spinae, serratus anterior, and pelvic anterior tilt angles were investigated during the prone bridge exercise with step boxes of different heights under the feet. A total of 18 healthy, physically active female volunteers completed the normal prone bridge exercise (NP), prone bridge exercise with a low step box (PL), and prone bridge exercise with a high step box (PH).

The PL condition caused significant increases in the activity of the internal oblique muscles compared with the NP condition (P < 0.05). PL and PH, which used step boxes, showed significantly greater activation in the serratus anterior compared to the NP (P < 0.05). The pelvic anterior tilt angle during PH was significantly greater than that during PL or NP (P < 0.05).

The high step box increased the pelvic anterior tilt angle with no additional abdominal muscle activity. The prone bridge exercise could be effective by adopting horizontal position between upper and lower body, compared to inclined lower body and general position.

To investigate the influence of two different active ankle positions during training on the strengths of knee extensors and flexors.

A sample of 21 healthy adults was randomized into ankle dorsiflexion (AD, N= 11) and ankle plantarflexion (AP, N= 10) training groups. Subjects were trained isokinetically and concentrically in knee extension and flexion under these two actively fixed, contracted ankle conditions, four times a week for three weeks.

AD group showed significant strength improvements in both peak moment and total work. These improvements were also higher significantly, between 29-59% compared to those gained by AP group.

Active ankle dorsiflexion during concentric isokinetic knee strength training may be more efficient for improving knee extensors and flexors strength than a plantarflexed position.

Regular physical activity is an important health factor, but intense physical stress can increase the risk of heart disease.

Our aim was to determine the potential cardiac repercussions of, and the oxidative stress resulting from a maximal eccentric isokinetic exercise and a 1-hour treadmill run at 75% V ˙ O₂ max (maximal exercise done 6 weeks before).

Twelve young sedentary healthy subjects randomly performed two tests separated by 6 weeks: 1) 3 sets of 30 maximal eccentric isokinetic contractions of the quadriceps; 2) a 1-hour running on treadmill at 75% V ˙ O_2max max. We drew blood samples just before each exercise (T1), and just after (T2), 3 hours after (T3), and 24 hours after (T4) the end of each exercise to measure cardiac and oxidative stress biomarkers.

In the running group, we observed significant differences for myoglobin (T3: 145 ± 80 μ g/L), creatinine kinase(T4: 593 ± 350 mg/L), oxidized glutathione (T2: 22 ± 15.6 μmol/L), and highly sensitive cardiac troponin T, (T3: 0.051 ± 0.038 ng/mL). In the isokinetic group, we observed significant differences for myoglobin (T3:1419 ± 2533 mg/L), creatine kinase (3303 ± 7159 mg/L), and oxidized glutathione (T4:24 ± 14 μ mol/L). Between isokinetic exercise and running, we observed significant differences for uric acid(p< 0.05, running > eccentric), myoglobin (p< 0.05, ditto), NT-proBNP (p< 0.05, ditto), hsTnT (p< 0.01, ditto), and oxidized glutathione(p< 0.05).

As cardiac biomarkers appear practically unmodified after the isokinetic exercise, despite the considerable oxidative stress, we suggest that the application of intense maximal eccentric isokinetic exercise, when indicated, should be safe for most patients including those whose cardiac status is unknown. On the other hand, the increase in cardiac biomarkers observed after running, could reflect leakage of these biomarkers from the cytosolic pool of cardiac cells, linked to membrane damage, rather than the result of a major injury and hence running is supposed to be a safe practice. However, since sudden death during running has been previously described, assesment of the cardiac biomarkers and a follow-up by a sport doctor is important especially if there is a cardiac family history.

A single measure to characterize overall muscle strength is advantageous because it saves time and costs of evaluation. For this reason, the back-leg-chest (BLC) strength might be an appropriate single measure in characterizing total body strength.

To assess the test-retest reproducibility and smallest real difference (SRD) of the BLC dynamometer in healthy adults and adolescents and to examine whether handgrip, knee-extensor and knee-flexor strength predict BLC strength in healthy adults.

Forty-five adults and 58 adolescents were recruited. In a first session back-leg-chest strength, handgrip strength, and additionally, in adults, isometric knee-extensor strength, and knee-flexor strength were measured. In a second session, 2-5 days later, BLC strength was measured again for test-retest reproducibility.

Inter-session correlations of BLC strength were high (all r's and ICC's > 0.92). Bland-Altman-plots showed high agreement. The SRD and SRD% were between 14-26, and 19% and 26% respectively. Strength variables (handgrip, knee-extensor, and knee-flexor strength) explained 87% of the variance in BLC strength. A stepwise linear regression showed that dominant knee extensor and flexor strength were the most important significant predictors of BLC strength (r² = 0.86).

This study demonstrated that the BLC dynamometer has reasonably high test-retest reproducibility and hence may serve in some pertinent situations to be an appropriate tool for clinical, basic and applied research.

The purpose of this study was to compare activation of the upper body musculature during the barbell bench press at varying training intensities.

Twelve young, resistance-trained men performed sets of the bench press to momentary muscular failure with two different loads: a high-load(HIGH) set at 80% of 1RM and a low-load (LOW) set at 50% 1RM. Exercise order was counterbalanced so that half the subjects performed the LOW condition first and the other half performed the HIGH first. Surface electromyography (EMG) was used to assess mean, peak, and iEMG muscle activation of the anterior deltoid, triceps brachii, and sternal and clavicular heads of the pectoralis major.

The main effects for trials were significant for mean EMG (p < 0.001) and iEMG matched (p < 0.001) favoring HIGH and iEMG total favoring LOW(p = 0.001) across all muscle groups in both conditions with varying effect sizes. All other main effects and interactions were not statistically significant.

Despite similarities in peak EMG amplitude, the greater results for mean and iEMG matched in HIGH suggests that heavier loads may produce greater muscle activation.

Respiratory muscles are important for exercise tolerance. Respiratory muscle fatigue (RMF) has a negative influence on exercise performance.

The aim of the present study was to examine the effects of a core strength training (CST) program on the RMF following incremental exercise.

Thirty male volleyball players participated in the study. The subjects were divided into two groups as experimental group (EG, n = 15) and control group (CG, n = 15). An eight-week CST program was implemented in the EG. The CG subjects participated in their respective sport training routine. The maximal inspiratory pressure (MIP) was measured twice at the baseline and endline incremental exercise both before (pre-test) and after(post-test) the eight weeks. A reduction in the MIP between the baseline and endline incremental exercise was considered to be indicative of the RMF.

There was a significant decrease in the MIP at the baseline and endline between the pre- and post-tests of both groups (p < 0.05). An increment in the MIP was found at the baseline between the pre- and post-tests in the EG (p < 0.05). There was no change in the RMF between the pre- and post-tests in the CG (p > 0.05). A significant decrease in the RMF was observed between the pre- and post- tests in the EG after the eight-week CST program (p < 0.05).

These variations indicate that core strength training may positively affect both the strength and fatigue of respiratory muscles.

Variations in both afferent proprioceptive information and efferent motor responses of the shoulder have been separately reported in overhead athletes.

We used a validated force platform method to examine shoulder sensorimotor control adaptation to overhead sports by analysing the change in Center of Pressure (CoP) in overhead athletes compared to control subjects.

Thirty healthy subjects were divided into four groups: squash players (SG), javelin throwers (JG) and two representative matched control groups of nonathletic healthy subjects, respectively. CoP displacements were measured by a force platform in the upper limb weight-bearing position with the lower limbs resting on a table up to the anterior superior iliac spines.

There were significant side-to-side differences for SG(P< 0.05); while not for JG and control groups. There were higher stabilometric values on the dominant side for SG and JG than their respective controls (P< 0.05).

These preliminary results suggest that the thrower's shoulder variations could include and/or induce a deficiency in shoulder sensorimotor control of the throwing side.

Patients with end-stage renal disease (ESRD) have poor physical performance and reduced exercise capacity due to frequent haemodialysis treatments.

The aim of the study was to determine the effectiveness of a three-month endurance training programme in patients with ESRD.

In order to improve both functional fitness and skeletal muscle properties, movement therapy-cycle ergometer, was applied in eligible ESRD patients during dialysis. The study included 40 dialysis patients, but only 27 patients completed the full three-month training during each haemodialysis treatment. Before and after training, all patients underwent observations according to the established protocol: functional capacity - Six-Min Walk Test, agility - Timed Up and Go test, and muscle strength testing under isokinetic conditions at 60, 180 and 300°/s.

Patients covered significantly longer distances in the 6MWT with a higher gait intensity after the 3 months training programme: the 6MWT increased from 360.8 to 390.2 m and metabolic equivalent from 2.74 to 2.85. The TUG significantly decreased in both women and men: from 9.07 to 7.51 s, and from 9.64 s to 7.4 s, respectively. The knee extension peak moment at 60 and 180°/s was significantly higher in women than in men following training. In addition, the women demonstrated more significant changes in flexor muscles at all angular velocities.

Three-month endurance training was effective in patients with ESRD in improving both functional fitness and skeletal muscle properties.

Worksite exercise to promote health is a relatively new concept in the industries of developing countries.

The aim of this study was to investigate the first-time feasibilities and effects of worksite exercises on physical capabilities of workers in an industry with limited sport facilities.

A randomized controlled-study was conducted. Ninety-one female workers were randomly assigned to one of the three study groups: two exercise groups and a control group. The workers in the exercise groups participated in group exercises 3 times per week. Maximal oxygen consumption (VO₂max), the level of hand skill, and hand grip strengths of the workers were measured before and after the 8-week intervention.

Approximately 75% of the workers (n= 68) completed the study. Adherence was higher in the exercise groups. Overall, no improvement was observed in the control group. VO₂max increased in both exercise groups (p< 0.05) but no difference was recorded between the groups. The level of hand skill was the least affected in all groups. Strengthening exercises conducted with elastic bands were superior to the repetitive movements in terms of strength gains.

Exercises capable of improving physical fitness and strength can be integrated into the usual workflow of an industrial workplace with minimal cost. Ensuring sport facilities and instruments during all working hours may improve adherence to worksite exercises.

Hamstring:quadriceps ratios (HQRs) have been studied as potential markers for an athlete's risk of injury, but little is known about how sport-specific experience affects HQRs.

This study compared isokinetic and isotonic strength measures, including determining HQRs, between American collegiate male rugby athletes with at least two years of experience (XP; n= 10) and those with less than two years of experience (IN; n= 14).

Isokinetic concentric (ConH) and eccentric (EccH) hamstring and concentric only quadriceps (ConQ) strength was measured at 60 and 180°/s. The strength ratio: Hcon/Qcon (HQR), was calculated for both velocities, HQR₆₀, HQR₁₈₀, while the strength ratio: Hecc/Qcon, the dynamic control ratio (DCR), was likewise calculated, DCR₆₀ and DCR₁₈₀. The isotonic strength was assessed via squat 1-repetition maximum. Analysis of covariance was used to examine differences between IN and XP while body weight and age served as the covariates.

No significant differences were noted between groups in isokinetic or isotonic strength. However, a significant difference was observed in DCR₆₀ (p = 0.047) between the two groups, with XP (0.94 ± 0.11) being greater than IN (0.81 ± 0.16).

In view of the preliminary nature of this study, the implication of this finding is yet obscure. However, given the role of the DCR in an underlying proneness to injury, we suggest that a more comprehensive study with a substantial follow-up period is undertaken for uncovering the potential importance of this ratio vis-à-vis other major functional parameters as well as injury prediction and assessment of rehabilitation.

Typical judo exercise consists of many acyclic, intermittent activity involving different types of muscle contractions, which makes monitoring judo trainings' process effectiveness challenging. The following study applied the near-infrared spectroscopy(NIRS) as a diagnostic tool in highly-trained judo athletes during an interval exercise, simulating the intermittent physical activity of a judo match. It was also designed to examine, whether muscle oxygenation, cardio-respiratory fitness capacity, and acid-base status differs between female (FJT) and male (MJT) athletes.

Judokas completed the same exercise protocol - a triple Wingate test separated by 4-minute rests. Before, directly after each WAnT as well as 15 minutes and 1 hour after the third WAnT, blood lactate (LA) and acid-base balance were determined. During the testing session the breath-by-breath pulmonary gas exchange method was used.

Recorded values of concentration changes in oxyhemoglobin (O₂Hb), deoxyhemoglobin (HHb) and absolute measure of O₂Hb saturation represented as tissue oxygenation index (TOI) revealed significant differences between groups (p≤ 0.05). Significant differences among cardio-respiratory factors were only noted between minute ventilation, and respiratory exchange ratio. Differences in blood lactate, HCO3 ^- , and arterial pH were noted after the second and third test as well as 15 minutes after the protocol's completion.

Collected data indicate that muscle oxygenation during the supramaximal exercise differed between genders, likely due to the influence of blood lactate accumulation on oxygen unloading and reduction in blood flow. Using NIRS, metabolic differences between groups were non-invasively determined, with the recorded data confirming the significance of an aerobic metabolism in judo, even during high-intensity exercise.

Despite widespread use of 6 and 30 second Wingate anaerobic tests (WAnT), performance reliability of these protocols over repeated trials in active males and females has not been determined.

This study assessed the performance reliability and test sensitivity of the 6 s and 30 s WAnT.

Twenty physically active participants (10 males and 10 females) completed a 6 s and 30 s WAnT against 7.5% body mass resistance on four occasions.

Peak power output (PPO) and mean power output (MPO) did not differ across trials for either gender. Male PPO in both sprint durations demonstrated random variation (standard error of measurement (SEM)) ≤ 3.9% in all between-trials comparisons. For MPO, SEM was ≤ 2.9% in all comparisons. For females, random variation in PPO in both sprint durations was lower in trial 3-4 than earlier pairs of trials. MPO between trials in the 6 s sprint was variable, with the smallest variation between trials 1-2. For the 30 s sprint, MPO was more stable across trials. Across all four trials, only MPO in the 30 s test for males displayed good test sensitivity.

In conclusion, familiarisation may not be required to establish consistent performance in physically active males or females during the 6 and 30 s WAnT. Furthermore, general marginal test sensitivity in both tests and genders suggests that results of WAnT in physically active participants should not be used to investigate the genuine effect of an intervention.