Jaan Ereline

Functional Performance, Maximal Strength, and Power Characteristics in Isometric and Dynamic Actions of Lower Extremities in Soccer Players

Requena, B, González-Badillo, JJ, Saez de Villareal, ES, Ereline, J, García, I, Gapeyeva, H, and Pääsuke, M. Functional performance, maximal strength, and power characteristics in isometric and dynamic actions lower extremities in soccer players. J Strength Cond Res 23(5): 1391-1401, 2009-The purposes of the present study were to determine muscle strength and power output characteristics in a group of professional soccer players and to identify their relationships with 2 functional performance tests (vertical jumping height and 15-m sprint time). Maximal strength and power indices attained against different loads in barbell back squat exercise, isometric maximal force of the knee extensor and plantar flexor muscles, isokinetic peak torque of the knee extensors muscles, vertical jumping height in squat and counter-movement jumps, and 15-m sprint time tests were assessed in 21 semiprofessional soccer players (age 20 ± 3.8 years). Correlation analyses were performed to examine the relationship between each of these measures. The main results of the present study were that (a) maximal power in concentric half-squat exercise was attained with a load of 60% of 1 repetition maximum, representing 112% of body weight; (b) the performance in the functional tests selected was significantly related with all the half-squat variables measured, especially with loads of 75-125% of body weight; and (c) low to nonsignificant correlations were found between functional tests performance and isometric and isokinetic muscle strength measures. It was concluded that in semiprofessional soccer players (a) isometric and isokinetic muscle strength assessed in an open kinetic chain were not movement-specific enough to predict performance during a more complex movement, such as jump or sprint and (b) concentric half-squat exercise was principally related with the functional tests selected when it was performed against external loading within the range of the load in case of which the maximal power output was attained.

Twitch contraction properties of plantar flexor muscles in pre- and post-pubertal boys and men.

Abstract This study compared electrically evoked twitch contraction characteristics of the plantar flexor muscles in pre-pubertal (11-year-old) and post-pubertal (16-year old) boys, and young (19- to 23-year-old) men. The posterior tibial nerve was stimulated by supramaximal square-wave pulses of 1 ms duration at rest and after brief (5 s) isometric maximal voluntary contraction (MVC) of the plantar flexor muscles, i.e. during post-activation potentiation. Men had higher MVC force than boys and post-pubertal boys higher than pre-pubertal boys. Pre-pubertal boys had lower peak twitch forces (Pt) at rest and when potentiated compared with post-pubertal boys and men, whereas no significant differences were found between post-pubertal boys and men. Pre-pubertal boys had higher ratios of Pt at rest and potentiated Pt to MVC force than post-pubertal boys and men. No age-related differences were obtained in post-activation potentiation, rest and potentiated twitch contraction and half-relaxation time, and MVC force relative to body mass. The main findings of the study were that puberty is characterized by increased muscle force-generating capacity with no change in twitch potentiation and time-course characteristics, and that twitch force-generating capacity develops in an adult-like pattern after puberty.

RELATIONSHIP BETWEEN POSTACTIVATION POTENTIATION OF KNEE EXTENSOR MUSCLES, SPRINTING AND VERTICAL JUMPING PERFORMANCE IN PROFESSIONAL SOCCER PLAYERS

Requena, B, de Villarreal, ESS, Gapeyeva, H, Ereline, J, García, I, and Pääsuke, M. Relationship between postactivation potentiation of knee extensor muscles, sprinting and vertical jumping performance in professional soccer players. J Strength Cond Res 25(2): 367-373, 2011-Little is known about the relationship between postactivation potentiation (PAP) in human muscles, assessed by enhancement of twitch torque after a conditioning maximal voluntary contraction (MVC), and performance in activities requiring power and speed. Moreover, no studies have assessed PAP in soccer players who train power and endurance simultaneously. The purpose of the present study was to examine the relationship between twitch PAP in knee extensor (KE) muscles, and sprinting and vertical jumping performance in soccer players. Fourteen professional male soccer players with mean (SD) age 20.0 (3.6) years, height 177.9 (6.9) cm and body mass 70.5 (5.7) kg) were tested for 15-m sprint time, vertical jump height in countermovement (CMJ) and squat (SJ) jumps. PAP in KE muscles was induced by a 10-s isometric MVC. Electrically evoked twitches of KE muscles were evoked before and after the conditioning MVC. Immediately after the conditioning MVC, twitch peak torque (PT) and maximal rates of torque development and relaxation were significantly potentiated. A significant negative correlation was found between 15-m sprint time and jump height in CMJ (r = −0.63) and SJ (r = −0.57). PAP of twitch PT correlated significantly positively with jump height in CMJ (r = 0.61) and SJ (r = 0.64), and negatively with 15-m sprint time (r = −0.59). In conclusion, twitch PAP in KE muscles was significantly correlated with performance in vertical jumping and sprinting in male professional soccer players, whereas the magnitude of PAP in soccer players was similar to that observed previously in power-trained athletes.

Effect of creatine supplementation during rapid body mass reduction on metabolism and isokinetic muscle performance capacity.

Abstract Well-trained subjects (n=6) were studied before and after losing a mean 3.0%–4.3% of body mass to determine whether muscle performance could be maintained or even enhanced by dietary creatine supplementation. During a 5-day period of loss of mass the subjects were randomly assigned to a creatine or placebo supplemented diet. All the subjects were measured before and after loss of mass on both supplements for isokinetic peak torque (PT) and work at peak torque (WPT) of knee extensors, also for intermittent high intensity working capacity of the same muscle group. The latter test consisted of submaximal isokinetic knee extensions at an angular velocity of 1.57 rad · s−1 for 45 s at the rate of 30 contractions each min (submaximal work, Wsmax) followed by 15-s maximal effort (maximal work, Wmax). Total duration of the test was 3 min. Haematocrit was measured and haemoglobin, ammonia, lactate, glucose and urea concentrations were analysed in blood samples obtained at rest and after cessation of muscle performance tests. The results indicated that creatine supplementation in comparison with placebo treatment during rapid body mass reduction may help to maintain muscle PT and WPT at high angular velocities, not influencing Wmax and the rate of fatigue development during Wmax, but affecting adversely Wsmax. Within the limitations of the present study the reasons for the partially detrimental effect of creatine administration remain obscure, but it is suggested that impaired creatine uptake in muscle during body mass loss as well as creatine induced changes in muscle glucose and glycogen metabolism may be involved.

Twitch contractile properties of plantar flexor muscles in power and endurance trained athletes.

Abstract This study compared twitch contractile properties of plantar flexor muscles among three groups of 12 subjects each: endurance and power trained athletes and untrained subjects. The posterior tibial nerve was stimulated by supramaximal square wave pulses of 1-ms duration. Power trained athletes had higher twitch maximal force, maximal rates of force development and relaxation and also maximal voluntary contraction (MVC) force. The trained subjects had a smaller twitch maximal force: MVC force ratio and shorter twitch contraction and half-relaxation times than the untrained subjects with no significant differences between the two groups. Thus, the short time for evoked twitches in the athletes compared to the untrained subjects would seem unrelated to the type of training. It is concluded that power training induces a more evident increase of muscle force-generating capacity and speed of contraction and relaxation than endurance training.

Lower limb performance in older female patients with Parkinson’s disease

Aims: This study examined lower limb performance in older sedentary patients with Parkinson’s disease (PD). Methods: Fourteen female patients with mild to moderate PD and 12 age-matched controls were included in this study. The force preparation and production of the knee extensor muscles during maximal isometric contraction were measured by dynamometric chair. Two force plates were used to measure the chair rising performance. Results: PD patients had longer visual reaction time during performing maximal isometric contraction,and lower maximal isometric force (MF) and rate of force development of the knee extensor muscles compared with controls. However, MF relative to body weight (BW)did not differ significantly in PD patients and controls. A longer chair rising time and lower maximal rate of vertical ground reaction force (VGRF) development while rising from a chair were found in PD patients compared with controls. No significant differences in maximal VGRF, and the sum of maximal VGRF of the right and left legs relative to the BW while rising from a chair were observed between the groups. In PD patients, chair rising time correlated negatively with MF of the knee extensor muscles. PD subjects also showed a positive correlation between the BW-related maximal VGRF while rising from a chair and MF of the knee extensor muscles relative to BW. Conclusions: These data suggest that subjects with PD are more deficient in the regulation of force-time parameters, rather than simply in force production of the knee extensor muscles.

Spinal curvature and trunk muscle tone in rhythmic gymnasts and untrained girls

The aim of this study was to compare spinal curvature and muscle tone characteristics in elite female rhythmic gymnasts (n = 32) and untrained controls (n = 48). Results showed that the angles of lumbar lordosis (LL) and thoracic kyphosis (TK) were lower (p < 0.001) in gymnasts in comparison with the control group. It was evident that the vertebral column of gymnasts had straightened in thoracic as well as in lumbar part of the spine. The trunk flexors in gymnasts were undertoned, the tone of rectus abdominis muscle was lower (p < 0.001) in gymnasts compared to that of the control group, while tone of erector spinae muscle (trunk extensor) was not differed from the control group. The tone of spinal muscles was higher (p < 0.001) than that of abdominal muscles in gymnasts, whereas the tone of these muscles did not differ significantly in controls. In the control group, the tone of trunk flexor and extensor muscles were in balance, whereas in gymnasts it was imbalanced. The indicator of tone imbalance of the trunk flexor and extensor muscles correlated negatively with the difference in body height in supine and standing positions (L) (r = −0.66, p < 0.001) for the group of gymnasts. In gymnast, TK and LL correlated negatively with Oswestry score (r = −0.68, p < 0.05 and r = −0.66, p < 0.05, respectively) and positively with L (r = 0.63, p < 0.05 and r = 0.60, p < 0.05 respectively). This indicates that the more rigid vertebral column, flattened in thoracal and lumbar part that appeared in gymnasts, associated with imbalance in muscle tone and low back pain (LBP). In 50% of measured gymnasts, LBP incidence

Back extensor muscle fatigability in chronic low back pain patients and controls: Relationship between electromyogram power spectrum changes and body mass index.

Back extensor muscle fatigability and its relationship to body mass index (BMI) was measured in 12 chronic nonspecific low back pain (CNLBP) patients (7 women and 5 men) and 12 healthy age-and gender-matched controls. Subjects performed Sørensen back isometric endurance test until exhaustion while EMG spectral mean power frequency (MPF) over the lumbar erector spinae muscle and endurance time were recorded. The CNLBP patients had significantly shorter endurance time than healthy controls. Spectral MPF significantly declined as time of isometric contraction progressed. Relative decrease of the MPF per minute (MPF slope) for left and right side, and pooled MPF slope was significantly higher in CNLBP patients compared with controls. In CNLBP patients the isometric endurance time correlated significantly negatively with BMI (r=-0.71). In controls BMI correlated significantly positively with MPF slopes of left (r=0.68) and right (r=0.57) side, and pooled MPF slope (r=0.62).

Relationship between leg extensor muscle strength and knee joint loading during gait before and after total knee arthroplasty

OBJECTIVE The aim of the present study was to evaluate an isometric maximal voluntary contraction (MVC) force of the leg extensor muscles and its relationship with knee joint loading during gait prior and after total knee arthroplasty (TKA). METHODS Custom-made dynamometer was used to assess an isometric MVC force of the leg extensor muscles and 3-D motion analysis system was used to evaluate the knee joint loading during gait in 13 female patients (aged 49-68 years) with knee osteoarthritis. Patients were evaluated one day before, and three and six months following TKA in the operated and non-operated leg. RESULTS Six months after TKA, MVC force of the leg extensor muscles for the operated leg did not differ significantly as compared to the preoperative level, whereas it remained significantly lower for the non-operated leg and controls. The knee flexion moment and the knee joint power during mid stance of gait was improved six months after TKA, remaining significantly lowered compared with controls. Negative moderate correlation between leg extensor muscles strength and knee joint loading for the operated leg during mid stance was noted three months after TKA. CONCLUSIONS The correlation analysis indicates that due to weak leg extensor muscles, an excessive load is applied to knee joint during mid stance of gait in patients, whereas in healthy subjects stronger knee-surrounding muscles provide stronger knee joint loading during gait. LEVEL OF EVIDENCE III (correlational study).

Effect of post-tetanic potentiation of pectoralis and triceps brachii muscles on bench press performance.

The effect of post-tetanic potentiation (PTP) induced in the pectoralis and triceps brachii muscles by high-frequency submaximal percutaneous electrical stimulation (PES) on average and maximal power attained in bench press throwing was measured in 12 healthy men. Three PES regimens were used: (a) a 7-second and (b) a 10-second trial at 100 Hz, and (c) an intermittent trial with 8 1-second tetanic trains at 100 Hz with rest periods of 20 seconds. Only nonsignificant (p > 0.05) increase was observed in average power at 8 minutes and in maximal power at 5, 8, and 11 minutes after tetanus after 7-second trial, and in maximal power at 5 and 8 minutes after tetanus after an intermittent trial. These data indicate that PES application was a noneffective stimulus for increased bench press performance. A great interindividual variability response was observed and, therefore, PTP induction for improving upper-body muscle performance needs further experiments.