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At least 235 records · Page 13Linked to original sources
PubMed1997

Fatigue-related EMG responses of trunk muscles to a prolonged, isometric twist exertion.

OBJECTIVE: To determine the responses of the trunk muscles to fatigue during sustained, isometric axial torque exertions. DESIGN: Electromyographic (EMG) amplitude and frequency parameters were used to investigate the effects of prolonged contractions on the recruitment patterns of trunk muscles, with special emphasis on those antagonistic and stabilizing muscles not contributing directly to the required axial torque. BACKGROUND: High levels of muscle coactivity have been observed during axial torque generation in the trunk. It has been suggested that this serves to enhance postural stability of the spine during potentially injurious twist exertions. Muscle fatigue decreases force-generating capacity but the resulting effects on muscle recruitment, and the subsequent consequences for postural stability, have not been explored previously during the production of axial torques in the spine. METHODS: Eleven male and 11 female subjects maintained an isometric axial torque exertion to the left (40% of maximum) until volitional exhaustion in an upright standing posture. Maximum axial torques were measured before and after the trial. The average EMG amplitude (AEMG) and mean power frequency (MPF) of seven bilateral trunk muscles (representing agonists, antagonists and trunk stabilizers) were continuously monitored throughout the trial. RESULTS: The average decrease in maximum torque was 18.5% and the average endurance time was 163 +/- 52 s. Evidence of muscle fatigue was provided by significant MPF decreases in 12 of the 14 muscles monitored (P < 0.05) with a overall average decrease of 20.4%. There was a significant increase in AEMG with time for 11 of the 14 muscles monitored (P < 0.05). These increases in activation were linked to increases in muscle force for most of the antagonistic and stabilizing muscles. Gender effects were rarely observed. CONCLUSIONS: Fatigue results in an change in the recruitment patterns of trunk muscles. Muscles serving as antagonists and trunk stabilizers during prolonged axial twist exertions increased their force levels in response to fatigue.

Journal Article↗
PubMed1998

Short-term temperature changes influence the force exerted by superelastic nickel-titanium archwires activated in orthodontic bending.

BACKGROUND: Alterations in mouth temperature may lead to changes in the force exerted by an activated superelastic wire. It has been assumed that variations in archwire stiffness associated with short-term cooling or heating are transient. This investigation studied the effect of short-term cooling or heating on the bending force exerted by nickel-titanium archwire. MATERIAL AND METHODS: Six rectangular superelastic wires and one conventional nickel-titanium wire were tested in bending at 37 degrees C. The test specimens were deflected 0.5 mm, and the bending force was measured continually. The activated specimens were subjected to cold (10 degrees C) or hot (80 degrees C) water under constant deflection, simulating an inserted archwire that is subjected to cold or hot drinks or food during a meal. RESULTS: The conventional nickel-titanium wire was marginally affected by brief cooling or heating. In contrast, some of the superelastic wires were strongly affected by short-time application of cold or hot water. Whereas the effect of brief heating disappeared quickly, some wires continued to exert sub-baseline bending forces (up to 32% less) after short-time application of cold water and showed little or no tendencies toward increase even after 30 minutes of postexposure restitution (up to 43% less). CONCLUSIONS: Short-term exposures to hot liquid increased the bending force exerted for a given deflection transiently. The effect of short-term exposures to cold liquid was not always transient; the bending force remained sub-baseline for a number of the thermosensitive wires tested for a prolonged time.

Dental Alloys↗
PubMed1997

Catabolite repression of the Bacillus subtilis gnt operon exerted by two catabolite-responsive elements.

Catabolite repression of Bacillus subtilis catabolic operons is supposed to occur via a negative regulatory mechanism involving the recognition of a cis-acting catabolite-responsive element (cre) by a complex of CcpA, which is a member of the GalR-Lacl family of bacterial regulatory proteins, and the seryl-phosphorylated form of HPr (P-ser-HPr), as verified by recent studies on catabolite repression of the gnt operon. Analysis of the gnt promoter region by deletions and point mutations revealed that in addition to the cre in the first gene (gntR) of the gnt operon (credown), this operon contains another cre located in the promoter region (creup). A translational gntR'-'lacZ fusion expressed under the control of various combinations of wild-type and mutant credown and creup was integrated into the chromosomal amyE locus, and then catabolite repression of beta-galactosidase synthesis in the resultant integrants was examined. The in vivo results implied that catabolite repression exerted by creup was probably independent of catabolite repression exerted by credown; both creup and credown catabolite repression involved CcpA. Catabolite repression exerted by creup was independent of P-ser-HPr, and catabolite repression exerted by credown was partially independent of P-ser-HPr. DNase I footprinting experiments indicated that a complex of CcpA and P-ser-HPr did not recognize creup, in contrast to its specific recognition of credown. However, CcpA complexed with glucose-6-phosphate specifically recognized creup as well as credown, but the physiological significance of this complexing is unknown.

Bacillus subtilis↗
PubMed2006

Vicarious perception of postural discomfort and exertion.

Perceived exertion and discomfort have been used extensively in ergonomics practice. Job incumbents typically rate their exertion on scales such as Borg's rated perceived effort (RPE) and their discomfort on scales such as Corlett and Bishop's body part discomfort scales (BPD). This study asks whether exertion and discomfort can be perceived by an external observer, i.e. is vicarious perception possible? Four participants (targets) performed 20 postural holding tasks selected from Ovako Working Posture Analysing System postures and gave RPE and BPD scores for each posture. Video clips of each target in each posture were shown to four expert ergonomists and 23 novices, who also gave RPE and BPD scores. Correlations between targets and observers scores were high, with significance exceeding p = 0.01. Observers were generally conservative, rating easy postures too high and difficult postures too low. All observers rated female targets higher than male targets. Female observers rated all targets higher then male observers. Vicarious perception of discomfort and exertion was possible, but there was not a one-to-one correspondence to ratings given by those experiencing the posture.

Adult↗
PubMed1995

Reproducibility of subjectively graded voluntary isometric muscle strength in unilateral and simultaneous bilateral exertion.

Reproduction error of voluntary isometric muscle strength that was graded subjectively by the subject was investigated under unilateral and bilateral conditions. Six kinds of tasks, i.e. elbow flexion, elbow extension, hand grip, second digit abduction, knee extension and leg extension were employed. It was clear that absolute error (AE) increased with increase of exerted muscle strength in both unilateral and bilateral conditions. Mean of AE in each task was 4-5% of maximal muscle strength in the task in unilateral conditions. Algebraic or constant error (CE) decreased with increase of exerted strength. Demands for smaller strength tended to overshoot and larger ones tended to undershoot. In bilateral conditions when the different levels of strength for each limb were required to be exerted, AE on the weaker side tended to be larger than that in unilateral conditions. Thus a possibility that magnitude of AE might be affected by amount of attention was suggested. The subjectively graded criterion strength for a specific required level, when the strength was expressed as relative to the maximal strength, was almost the same in every task within a subject although it was different between subjects. It is suggested that each subject might have an awareness of relative magnitude of exerted strength.

Arm↗
PubMed1999

Managing risk and exerting control: determining follow through with falls prevention.

PURPOSE/METHOD: This study used in-depth interviews to explore the perspectives of nine older women who had not followed through with environmental modification recommendations to reduce their risk of falls in the home. RESULTS: It was found that the core concept of 'exerting control' provided an understanding of their experience following an occupational therapy home visit. Exerting control was a behavioural, cognitive and affective process whereby the women made decisions about whether or not to follow through with environmental modification recommendations based on their knowledge of environmental risks, perceptions of degree of risk, perceived ability to mediate these risks through behaviour and the degree of freedom she had in decision making. Exerting control meant that the women made daily choices about their home environment which increased or decreased the risk of falls with identified home hazards. CONCLUSION: The findings suggest that, for some women, health professionals need to understand and work with the phenomenon of exerting control, in order to work with clients to reduce environmental hazards.

Accidental Falls↗
PubMed1992

Prognostic significance of silent exertional myocardial ischaemia in symptomatic men without previous myocardial infarction.

A total of 360 consecutive male patients with complaints of chest pain and documented coronary artery disease underwent a maximal exercise test combined with thallium myocardial scintigraphy. Patients with a history of previous myocardial infarction were excluded. During follow-up (46 months; from 12 to 96) 27 patients died and 26 had a first non-fatal myocardial infarction. The 6-year survival rate and the 6-year event-free rate were 81 and 71%. Four variables contributed independently to the prognosis (Cox Model): the number of diseased vessels, the angiographic ejection fraction, the age and a multivariate score of the exercise test. From these patients, 227 had an abnormal response to exercise (ST-segment depression greater than or equal to 0.1 mV); in 138 patients, angina pectoris was induced during exercise while 89 patients had no pain during exercise (silent ischaemia). These 89 patients with silent exertional ischaemia were matched to 89 patients with exertional angina pectoris, according to the above-mentioned four prognostic predictors. The two groups of patients had similar signs of ischaemia during exercise (ST-segment depression and thallium perfusion score). The 6-year survival rates (81 and 81.5%) and the 6-year event-free rates (71 and 70.5%) were similar in the two groups. Thus, in men without previous myocardial infarction, silent exertional ischaemia bears the same prognosis as exertional ischaemia attended by angina pectoris.

Adult↗
PubMed1996

Risk factors predicting exertional heat illness in male Marine Corps recruits.

A matched population-based case-control study was conducted on exertional heat illness (EHI) in male Marine Corps recruits in basic training at Parris Island, SC. Physical fitness and anthropometric measurements were obtained for 391 of 528 cases of EHI identified in this population during 1988-1992, and 1467 of 1725 controls matched to cases by initial training platoon. The risk for developing EHI increased with increase in body mass index (BMI = weight.height-2) as measured on arrival and with increase in time to complete a 1.5-mile run conducted during the first week. Recruits at highest risk for developing exertional heat illness had a BMI of 22 or more kg.m-2 and a 1.5-mile run-time for 12 of more minutes. These recruits had an eightfold higher risk for developing exertional heat illness during basic training when compared with those with BMI less than 22 kg.m-2 and 1.5-mile run-time under 10 min (P < 10(-6). Only one-fifth (18%) of male recruits met these criteria for high risk, but they accounted for nearly half (47%) of the exertional heat illness cases occurring during the 12-wk basic training course.

Adolescent↗
PubMed2002

Perceived exertion responses to novel elbow flexor eccentric action in women and men.

PURPOSE: The primary aim was to describe perceived exertion responses to different intensities of eccentric exercise in women and men. METHODS: 42 adults (21 men and 21 women, 7 per condition) completed elbow extension exercises with a weight corresponding to 80%, 100%, or 120% of maximal voluntary concentric strength. Total work was equated by manipulating the number of repetitions in the 80% (N = 45), 100% (N = 36), and 120% (N = 30) conditions. RESULTS: A two-way ANOVA showed significant main effects for the intensity and sex factors. Perceived exertion ratings were strongly dependent on exercise intensity, and women reported lower RPEs than men. A separate three-way mixed model ANOVA that included a repetition factor showed that perceived exertion ratings increased similarly across the first 30 repetitions in all exercise conditions. Significant partial correlations were found between mean RPE during the eccentric exercise bout, and the mean intensity of delayed-onset muscle pain measured from 12- to 72-h postexercise after controlling for the relative exercise intensity (r12.3 = 0.28) or the maximum concentric strength of the elbow flexors (r12.3 = 0.33). CONCLUSIONS: 1) for both women and men, there is a positive association between the intensity of eccentric exercise performed with the elbow flexors and RPE; 2) perceived exertion ratings increase significantly then plateau when repeated eccentric muscle actions are performed at constant, submaximal absolute intensities; 3) women rate eccentric exercise performed at the same intensity (relativized to MVC-C) as being less effortful compared with men; and 4) RPE during eccentric exercise can account for a small but significant amount of variability in delayed-onset muscle pain after statistically controlling for differences in strength or relative intensity.

Adult↗
PubMed2002

Lower torso muscle activation patterns for high-magnitude static exertions: gender differences and the effects of twisting.

STUDY DESIGN: Surface electromyographic signals were collected from 14 lower torso muscles while participants resisted high-magnitude static trunk moments applied in a variety of directions. OBJECTIVES: To obtain a description of muscle activations in response to large moment magnitudes and axial twisting, including levels of agonistic and antagonistic muscle cocontraction. To assess differences in lower torso muscle activation patterns associated with gender and trial repetition. SUMMARY OF BACKGROUND DATA: Back pain is associated with mechanical loads in the back. Biomechanical modeling of these loads is facilitated by knowledge of typical muscle activation patterns. Previous efforts in obtaining such data have often limited their scope to low-magnitude exertions or relatively simple scenarios. METHODS: Eight male and eight female participants, matched by height and mass, performed static exertions in an apparatus that immobilized their lower body while the activation levels of seven bilateral torso muscles were measured using surface electromyography. Activation patterns were analyzed to assess differences resulting from a variety of factors. RESULTS: No significant differences in activation patterns were found between genders or repetitions, but moment magnitude and direction elicited substantial differential responses. Good repeatability was found between trial repetitions, as indicated by intraclass correlation coefficients (>0.65). Significant synergistic muscle coactivation, large intersubject variability (mean coefficient of variation 82.2%), and consistent levels of antagonism ranging from 10% to 30% maximum voluntary exertions were observed. CONCLUSIONS: Individuals of different genders, but similar anthropometry, have comparable muscular reactions to complex torso loads, suggesting similar motor control strategies. Future spine models should consider that the variability in muscle recruitment patterns is larger between subjects than within subjects. High-magnitude exertions, especially those with moment loads in more than one plane, require most muscles to be active (>5%) and moderate levels of antagonism.

Adult↗
PubMed1990

The influence of spacers on forces exerted on the abutment teeth of complete mandibular overdentures.

The avoidance of lateral forces on overdenture retainers is essential to prevent pathological change in the supporting tissues of the root abutment. In this study, the influence of spacer thickness on the vertical and lateral forces exerted on overdenture abutments was examined clinically. Two subjects with an edentulous maxilla, two canines and a left first premolar remaining in the mandible were selected for the experiment. The anchor type attachment was embedded in the left canine portion of the denture base. The transducer used for the previous study (Ogata et al., 1990), was embedded in this left canine portion. The transducer could detect the magnitude and direction of lateral forces exerted on an abutment tooth parallel to the Camper's plane. The other transducer was embedded in the left first mandibular premolar area, and could detect vertical forces exerted on the abutment tooth perpendicular to the Camper's plane. Furthermore, the transducer could change the space between a denture base and an abutment tooth to 1.5 mm, 0.6 mm or 0.3 mm. Therefore measurements could be made in the same way as if three experimental dentures had been used with a different thickness spacer. Recordings of forces were taken during food chewing, using each spacer on the day of denture insertion and twice at intervals of 1-2 weeks thereafter. The results demonstrated that as spacer thickness decreased, the magnitude of the lateral forces decreased, while the magnitude of the vertical forces increased. These findings suggest that a large part of the lateral component of forces exerted on an abutment tooth could be converted into a vertical component by using a thinner spacer.

Bite Force↗
PubMed1990

Whether phenylephrine exerts inotropic effects through alpha- or beta-adrenoceptors depends upon the relative receptor populations.

Phenylephrine produced concentration-related positive inotropic responses in isolated left atria and papillary muscles of guinea-pigs and rats. In rat tissues, these responses were unaffected by propranolol but antagonized by prazosin and therefore mediated via alpha 1-adrenoceptors. The alpha 1-adrenoceptor agonist methoxamine also exerted positive inotropic effects in these rat tissues. The maximum alpha-adrenoceptor-mediated effect of methoxamine (relative to the isoprenaline maximum) was greater than that of phenylephrine in left atria (in the presence of propranolol), whereas in papillary muscles phenylephrine exerted the greater maximum. In guinea-pig papillary muscles, the response to phenylephrine was unaffected by prazosin but was antagonized by propranolol and therefore caused by stimulation of beta-adrenoceptors. Methoxamine had no effect in guinea-pig papillary muscles. Guinea-pig left atria produced biphasic concentration-response curves for phenylephrine, the lower portion being antagonized by phentolamine and was therefore alpha-adrenoceptor-mediated, while the upper portion was antagonized by propranolol and therefore beta-adrenoceptor-mediated. Methoxamine exerted a small inotropic response, the maximum of which was similar to that of the first component of the phenylephrine response. Phenylephrine was a partial agonist for the cardiac beta-adrenoceptor. The density of rat ventricular alpha-adrenoceptors was 4 times greater than beta-adrenoceptor density, as measured by [3H]-prazosin and [3H]-dihydroalprenolol binding. This explains why the responses of rat papillary muscles were alpha-adrenoceptor-mediated. In contrast, the density of beta-adrenoceptor binding sites in guinea-pig ventricles was 6 times greater than the alpha-adrenoceptor density. This explains why the phenylephrine responses were beta-adrenoceptor-mediated in guinea-pig papillary muscles. In the left atria of guinea-pigs, which displayed both alpha- and beta-adrenoceptor-mediated responses, the densities of alpha- and beta-adrenoceptor binding sites were similar. Thus, phenylephrine exerts positive inotropic effects through alpha- or beta-adrenoceptors depending upon their relative densities.

Animals↗
PubMed1996

Negative chronotropic and inotropic effects exerted by diadenosine hexaphosphate (AP6A) via A1-adenosine receptors.

1. Diadenosine hexaphosphate (AP6A) exerts vasoconstrictive effects. The purpose of this study was to investigate whether AP6A has any effect on cardiac function. 2. The effects of AP6A (0.1-100 microM) on cardiac contractility and frequency were studied in guinea-pig and human isolated cardiac preparations. Furthermore, the effects of AP6A on the amplitude of the L-type calcium current, on the adenosine 3':5'-cyclic monophosphate (cyclic AMP) content and on the phosphorylation of regulatory phosphoproteins, i.e. phospholamban and troponin inhibitor, were investigated in guinea-pig isolated ventricular myocytes. 3. In isolated spontaneously beating right atria of the guinea-pig AP6A exerted a negative chronotropic effect and reduced the rate of contraction maximally by 35% (IC20 = 35 microM). 4. In isolated electrically driven left atria of the guinea-pig AP6A exerted a negative inotropic effect and reduced force of contraction maximally by 23% (IC20 = 70 microM). 5. In isolated electrically driven papillary muscles of the guinea-pig AP6A alone was ineffective, but attenuated isoprenaline-stimulated force of contraction maximally by 23% (IC20 = 60 microM). Furthermore, AP6A attenuated the relaxant effect of isoprenaline. 6. In human isolated electrically driven ventricular preparations AP6A alone was ineffective, but attenuated isoprenaline-stimulated force of contraction by maximally 42% (IC20 = 18 microM). Moreover, AP6A attenuated the relaxant effect of isoprenaline. 7. All these effects of AP6A were abolished by the selective A1-adenosine receptor antagonist 1,3-dipropyl-cyclopentyl-xanthine (DPCPX, 0.3 microM), whereas the M-cholinoceptor antagonist atropine (10 microM) and the P2-purinoceptor antagonist suramin (300 microM) failed to abolish the effects of AP6A. 8. AP6A 100 microM had no effect on the amplitude of the L-type calcium current, but attenuated isoprenaline-stimulated L-type calcium current. The maximum of the current-voltage relationship (I-V curve) was shifted to the left by isoprenaline and additional application of AP6A shifted the I-V curve back to the right to the control value. The phosphorylation state of phospholamban and the troponin inhibitor was unchanged by AP6A alone, but was markedly attenuated by AP6A in the presence of isoprenaline. Cyclic AMP levels remained unchanged by AP6A, even after stimulation with isoprenaline. 9. In summary, AP6A exerts negative chronotropic and inotropic effects in guinea-pig and human cardiac preparations. These effects are mediated via A1-adenosine receptors as all effects were sensitive to the selective A1-adenosine receptor antagonist DPCPX. Furthermore, the effects of AP6A on cyclic AMP levels, protein phosphorylation and the L-type calcium current are in accordance with stimulation of A1-adenosine receptors.

Animals↗
PubMed1993

Cat hindlimb muscles exert substantial torques outside the sagittal plane.

1. We studied the contributions of several hindlimb muscles to ankle torque in adult cats deeply anesthetized with pentobarbital sodium. Isometric torques were measured with a multiaxis, force-moment sensor connected to the plantar surface of the foot. 2. Individual muscle torques were provoked by using a combination of muscle nerve stimulation and selective denervations and tenotomies. Torques were represented by three orthogonal components; defined as dorsiflexion/plantarflexion, inversion/eversion (rotation about the long axis of the foot), and toe-in/toe-out (rotation about the axis of the tibia). 3. Most of the muscles tested exerted substantial torques about more than one of the orthogonal axes, each of which shared a common origin centered midway between the medial and lateral malleoli. The lateral and especially the medial head of the gastrocnemius muscle exhibited large toe-out torques and eversion torques as well as the classical plantarflexion components. 4. The torque exerted by tibialis anterior was seen to oppose that of both medial and lateral gastrocnemius in each of the three directions. The toe-in and inversion torques exerted by tibialis posterior was opposed in these directions by both peroneus brevis and peroneus longus. Flexor hallucis longus exerted approximately 10 times more plantarflexion torque than did flexor digitorum longus; therefore, these two muscles cannot be considered pure synergists. 5. The major plantarflexors and dorsiflexor of the cat ankle joint contribute substantial torques outside the sagittal plane. Their opposing torques lead to increased joint stiffness; the net effect of coactivation of these muscles causes ground reaction forces oriented so as to maintain stability during quadrupedal stance.

Animals↗
PubMed1993

Recombinant human follicle-stimulating hormone is capable of exerting a biological effect in the adult hypophysectomized rat by reducing the numbers of degenerating germ cells.

There is considerable controversy as to whether FSH can, under normal circumstances, exert an effect to promote spermatogenesis in the adult rat. Recombinant human FSH (rhFSH) was used to answer a more limited question relating to whether FSH is capable of exerting a biological effect in promoting adult spermatogenesis. Can a pure preparation of FSH prevent the regressive changes seen after hypophysectomy (Hx) in a short term experiment? To answer this question, five groups of adult rats were used as follows: pituitary-intact animals, 3-day hypophysectomized (Hx), 3-day Hx given 3 mg testosterone propionate (T)/day for 7 days, 3-day Hx given 22 IU rhFSH for 7 days, and 3-day Hx given saline vehicle for 7 days. Testis weight, seminiferous tubule diameter, analysis of four degenerating germ cell types, the relative amount of lipid, and the levels of FSH receptors showed that FSH could, in a significant manner, prevent the regressive changes accompanying Hx. FSH was not as effective as T in doing so, because the FSH values were always intermediate between T-maintained animals and those after long term Hx. The Leydig cell was eliminated as a possible source of FSH-stimulated T promotion of spermatogenesis, given that morphometry and tissue T assays indicated that no additional production of T was elicited by rhFSH. The assay system used to enumerate degenerating germ cells proved a very sensitive indicator of the ability of hormones to maintain cell viability in short term experiments. The data not only show that FSH can exert a biological effect, but that this effect is qualitatively similar to that seen after the administration of T in terms of the maintenance of viability of specific germ cell types. A hypothesis is presented whereby FSH and T, although the former acting by a second messenger system and the latter by binding to nuclear receptors, can stimulate the genome to exert similar qualitative effects promoting the viability of germ cells.

Animals↗
PubMed2005

Perceived exertion during prepregnancy physical activity and preeclampsia risk.

PURPOSE: Studies have shown that absolute intensity of physical activity is associated with reduced risk of preeclampsia. This analysis was performed to examine whether relative intensity may also be related to preeclampsia risk. METHODS: Using data from a case-control study conducted from 1998 to 2002, the authors assessed the relation between perceived exertion (i.e., relative intensity) during usual recreational physical activity in the year before pregnancy and risk of preeclampsia. In a structured interview conducted during postpartum hospitalization, 244 preeclampsia cases and 470 normotensive controls provided details on their recreational physical activities in the year before pregnancy. RESULTS: Participants who reported feeling very strenuous to maximal exertion during usual prepregnancy physical activity were 78% less likely to have developed preeclampsia than those who reported negligible or minimal exertion (adjusted odds ratio 0.22, 95% confidence interval 0.11-0.44). A significant trend was noted of decreased preeclampsia risk with increased perceived exertion (P < 0.001). This association was independent of prepregnancy adiposity, and was also apparent among the subset of participants who did not meet physical activity guidelines in the year before pregnancy. CONCLUSIONS: In this study, relative intensity of recreational physical activity performed during the year before pregnancy was associated with a decreased risk of preeclampsia.

Adolescent↗
PubMedDate not supplied

Knee injuries in athletes. Review of exertion injuries and retrospective study of outpatient sports clinic material.

About one third of all sports injuries admitted to outpatient sports clinics concern knees. The incidence of different knee disorders in an outpatient sports clinic material and a review of the literature concerning the wide and problematic area of knee exertion injuries in athletes is presented. Exertion injury is defined as non-traumatic pain syndrome in the musculoskeletal system, including typical stress injuries and pain syndromes associated with physical activity but also has other important aetiological factors. 2762 athletes were admitted to the Turku Sports Medical Research Unit's outpatient sports clinic from 1976 to 1983 and 886 (32%) of them, 697 male and 189 female athletes, had suffered knee disorders. Football (soccer) [20.8%], long-distance running (13.1%), volleyball (11.6%), orienteering (7.6%) and ice-hockey (7.2%) had the highest incidence and the most common knee disorders were patellar apicitis (20.4%), Osgood-Schlatter's disease (10.1%), patellar chondropathy (10.0%), ligamentous sprains (9.0%) and meniscus tears (6.9%). The mean age of all athletes with knee disorders was 20.8 years. On an average each complaint caused 2.16 appointments. Careful evaluation of malalignments predisposing the athlete to exertion injury is necessary in the treatment of knee disorders and to avoid the recurrence of the exertion injury due to some biomechanical reason. The authors emphasise the importance of careful clinical examination. Although our review does not include detailed information about injuries originating in a single trauma, it is important to pick up the cases of ligamentous tears early so they can be appropriately repaired. Diagnostic and operative arthroscopy adds a new method in avoiding diagnostic errors and in shortening the postoperative rehabilitation.

Adult↗
PubMed2004

Lifting strengths in different exertion heights conditioned on extended legs.

This study recruited seven height-matched healthy males to examine their maximum isometric lifting strengths across 13 exertion heights, ranging from 25 cm to 133 cm in increment of 9 cm. The results showed a nonlinear (increasing-decreasing-increasing) strength-height relationship for all subjects. The subjects' lifting strength was strongest (mean 1253.2 N) at the exertion height of 61 cm and weakest (mean 454.1 N) at the exertion height of 115 cm. Due to a large variability of strength ratio for the weakest individual strength to the strongest individual strength across the 13 exertion heights, ranging from 59.6% to 83.7%, practitioners should be cautious when assessing workers' lifting capacity based on strength testing.

Body Height↗