The purpose of this study was to display increase in eccentric hamstring strength after 10-weeks training program. Secondly, if such an increase occurred, would this strength change result in altered landing kinetics and improved jumping performance? 27 recreational female athletes assigned into experimental (n = 14) and control (n = 13) groups. Baseline measures of landing kinetics were collected using a force plate, strength data and proprioceptive measurements were evaluated using an isokinetic dynamometer and vertical jump performance were determined by a jumping mat. Results indicated that NHST group increased their eccentric hamstring strength after eccentric strength training program (week-1 = 233.6&plusmn / 27.5, week-10 = 253.8&plusmn / 28.4 Nm/kgbw / p&lt / .05). The results demonstrated that there were significant differences in landing mechanics for NHST group. PVGRF (week-1 = 6.2&plusmn / 0.9, week-5 = 5.3&plusmn / 0.9 / p&lt / .05), PAPGRF (week-1 = 1.1&plusmn / 0.2 &amp / week-10 = 0.8&plusmn / 0.3 / p&lt / .05) and APImp results demonstrated significant differences in trained group (week-1 = 78.1&plusmn / 13.6 &amp / week-10 = 67.8&plusmn / 9.2 / p&lt / .05). NHST group exhibited significant increase in vertical jumping ability (week-1 = 0.25&plusmn / 0.0 &amp / week-10 = 0.27&plusmn / 0.0 cm / p&lt / .01). This study supported the following points: 1) increases in the eccentric hamstring strength were evident after NHST program, 2) the increases in isokinetic strength were sufficient to cause alterations in landing kinetics to decrease the applied joint forces, so the NHST program would be an influential factor in decreasing the lower extremity injuries, and 3) the increase in the efficiency of force transfer at the final take off phase of jumping contributed to a higher performance in vertical jump.

The purpose of this study was to investigate whether 3 days of dietary nitrate supplementation has positive effects on exercise performance and energy metabolism at rest and during strenuous knee exercise, and exercise recovery. The experimental protocol was a double blind, placebo-controlled, two-period, and within-subjects design. Fourteen healthy nonsmoking males (22.71 ± 0.72yr, 72.93 ± 2.35kg, and 47.67 ± 1.56 ml/kg/min VO2max) participated in the study. Two supplements (nitrate lozenge; NO-L or placebo; PLA) were orally administrated randomly at 48 and 24 hours before each trial day and again 40 minutes before each exercise trial. Total work, peak torque, and respiratory gases were automatically collected during repeated knee extensions/flexions (isokinetic concentric contractions with dominant leg; 4 sets of 28 repetitions at 180°/sec with 30 sec rest intervals) and recovery (6 contractions of 1 repetition maximum with 120 vii sec between contractions). For these results, peak torque, rate of fatigue, work efficiency, and rate of recovery were calculated. Blood specimens were collected at rest before and after the treatment, post exercise, and end of recovery to track the changes in blood glucose and lactate concentrations. There was a significant inverse correlation for total work during knee extension exercise and oxygen consumption (PLA: r = -.560 and NO-L: r = -.546; p < .01, respectively). During the exercise, RER was significantly higher for PLA compared with NO-L (PLA: 1.42 ± 0.02 vs. NO-L: 1.38 ± 0.02: p = .03). Work within each set and total work performed were higher for NO-L, but these differences were not significant. However, NO-L enhanced exercise efficiency by 3.3% when compared with PLA (PLA: 2497.5 ± 134.56 ft-lb/L/min vs. NO-L: 2578.7 ± 132.24 ftlb/L/min; p = .05). Extensor peak torque recovery rate slope was not significant, but meaningfully faster for NO-L (PLA: 2.39 ± 0.52% vs. NO-L: 3.06 ± 0.54%; p = .09) and significant interaction effect (p = .02) was found during recovery contractions, especially from contractions 2 to 3 (p = .03). It is also worth noting that differences in time to peak torque during knee extension exercise for NO-L and PLA approached significances (PLA: 0.213 ± 0.01 sec vs. NO-L: 0.200 ± 0.01 sec; p = .08). The results suggest that 3 days of dietary nitrate supplementation improves rate of exercise recovery and enhances work efficiency during vigorous resistance exercise. / text

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal

In male athletes from different sports, isokinetic knee extensor, and in orienteers also plantar flexor peak torque (PT), contractional work (CW) and integrated surface electromyograms (iEMG) were analysed. Single contraction PT, CW and iEMG in sprinters and marathon runners were signi­ficantly correlated to the cross-sectional area (CSA) of m. quadriceps, and to the Type II fibre area of m. vastus lateralis. When correcting PT, CW and iEMG for CSA of m. quadriceps, such correlations were found only for Type IIA fibre area at 180° s~1. Elec- tromyographically, m. vastus lateralis (biopsied muscle) was representative for m. quadriceps. Calculated optimal mean power (CW s~1) and electrical efficacy (CW/iEMG) approximated for sprinters 450° s-1 and for marathon runners 270° s~1, i.e. velocities at or above the upper limit of the dynamometers. In orienteers, plantar flexor PT increased during winter training, but decreased during competitive season. Knee extensor PT increased over the whole year. At 30 and 60° s~1 only knee extensor PT was negatively associated with the running velocity at onset of blood lactate accu­mulation (VOBLA)- Changes in VOBLA during winter period were negatively associated with changes in knee extensor PT at 180° s~1. During competitive season, changes in Vobla were negatively associated with the ratio quality : quantity running. In ice hockey players PT varied non-systematically with training and games. The biopsy specimens of marathon runners showed irregular fibre shapes, an in­creased amount of connective tissue and central fibre nuclei, indicating an early strain disease or functional adaptation to extreme demands. During repetitive contractions in sprinters and marathon runners, fatigue, i.e. slope of decline in CW, was significantly associated with the Type II fibre area of m. vastus lateralis. For knee extensors of sprinters, ice hockey players and orienteers, a steep de­crease in CW/iEMG was observed. In contrast, knee extensors of marathon runners and plantar flexors of orienteers showed an almost unaltered CW/iEMG throughout the test. The knee extensor endurance level (CW/iEMG) was significantly correlated to the maximal oxygen uptake. In orienteers, an increase in endurance level of both tested muscle groups during winter training parallelled an increase in VOBLA and V02obla- In hockey players, fatigue and endurance pattern (CW and CW/iEMG) changed non-systematically with training and games. In conclusion, isokinetic measurements and iEMG reflect the structural properties of the knee extensor muscles in sprinters and marathon runners. The demonstrated characteristics and changes in leg muscle function in different groups of athletes apparently reflect varying demands from different sports activities. / <p>S. 1-31: sammanfattning, s. 33-84: 6 uppsatser</p> / digitalisering@umu

The main purpose of this study was to investigate the relationship between human growth hormone (hGH) and two separate components of resistance exercise. Eight non-weight-trained subjects (23.33 ± 0.3 yrs) performed three force production trials (FPT), at different concentric workloads, and an 120% eccentric exercise trial (EET) on the Cybex 6000. Blood samples (3 mls) were taken pre- and post-exercise and analyzed for lactate, creatine kinase (CK) and hGH. Electromyographic (EMG) activity of the quadriceps muscle was recorded during each trial. The mean peak torque produced during the FPTs increased as work intensity increased but was the highest in the EET. The data for total work showed a proportional relationship with the intensity of the three concentric work loads but not the 120% EET. EMG activity of vastus medialis (VM) and rectus femoris (RF) measured during EET was 26% less than RF of 50% and 15% less than VL of 70% in FPT, respectively. The highest hormonal response occurred following the 120% EET. The hormonal response following the FPTs was highest in the 90% FPT with the two lower work intensity trials (50 and 70%) showing no clear hormonal response. Although the hGH response was the highest in the 120% EET, the post-exercise lactic acid levels in EET were 24% less than that of the 90% FPT. Creatine kinase (CK) activity was significantly elevated 36 hours after the last bout of EET which suggests that the eccentric exercise resulted in muscle damage. The results from concentric trials showed that muscle force generation, EMG, and lactic acid of the three different concentric trials were well correlated to the pattern of hGH secretion. However, only peak torque was consistent with the hGH response of the EET. The highest peak torque and hGH levels were achieved with eccentric exercise. The highest levels of fatigue, as a result of the combination of longer exercise time and overloading of the muscle during EET, may explain the higher hGH output. The muscle damage caused by the eccentric trial was enough to induce delayed onset of muscle soreness and may be the stimulus for the higher hGH output. The hGH response may facilitate repair of the muscular damage induced by eccentric exercise by promoting protein synthesis. / School of Physical Education

Knee function after more than 20 years post injury is rarely described and none of the few follow-up studies have evaluated functional performance tasks. This thesis investigated self-reported knee function, physical activity level, physical capacity and movement pattern in the long-term perspective (on average 23 years) in persons who had suffered a unilateral ACL injury, treated either with physiotherapy in combination with surgery (ACLR, n=33) or physiotherapy alone (ACLPT, n=37) and compared to age-and-gender matched controls (n=33).  This thesis shows that regardless of treatment, there are significant negative long-term consequences on self-reported knee function and physical activity more than 20 years after injury. In comparison to the controls, the ACL-groups (ACLR and ACLPT) had lower knee function as measured by the Lysholm score and the Knee injury and Osteoarthritis Outcome Score (KOOS). The persons with an ACL injury also had a lower knee-specific physical activity level (Tegner activity scale), while no differences were seen in general physical activity level (International Physical Activity Questionnaire, IPAQ) compared to healthy controls. Regarding physical capacity, both ACL groups showed inferior jump capacity in the injured leg compared to the non-injured leg. However, compared to controls the ACL-injured had a relatively good jump performance. Knee extension peak torque, concentric and eccentric, was also lower for the injured leg compared to the non-injured leg for both ACLR and ACLPT. In addition, the ACLPT group showed reduced eccentric knee flexion torque of the injured leg. The non-injured leg, on the other hand, showed almost equal jump capacity and strength as controls. Balance in single-limb stance (30s) was inferior in persons who had an ACL injury. This was true for both the injured and non-injured leg and regardless of treatment. Movement pattern during the one-leg hop was analysed by a set of kinematic variables consisting of knee angles (flexion, abduction, rotation) and Centre of Mass (CoM) placement in relation to the knee and ankle joints. Both ACLR and ACLPT displayed movement pattern asymmetries between injured and non-injured legs. In comparison to controls, the ACLR group had a similar movement pattern with the exception of larger external knee rotation at Initial contact and less maximum internal rotation during the Landing. ACLPT showed several differences compared to controls both regarding knee angles and CoM placement. The ACL-injured persons with no-or-low knee osteoarthritis (OA) had better knee function as reflected by higher scores on Lysholm and KOOS subscale ‘symptom’ compared to those with moderate-to-high OA. The degree of OA had no influence on reported physical activity level, jump capacity, peak torque or the kinematic variables.  In conclusion, this thesis indicates that persons with a unilateral ACL injury, regardless of treatment, have some negative long-term consequences e.g. self-reported knee function, knee-specific activity level, strength and balance deficits, when compared to age-and-gender matched controls. The results, however, also indicate that the ACL-injured can manage reasonably well in some jumps and general activity level but have an inferior performance in more knee-demanding tasks. The ACLR group had similar movement pattern with the exception of knee rotation, indicating that a reconstruction may restore the knee biomechanics to some extent. The ACLPT group on the other hand, seem to use compensatory movement strategies showing several differences compared to controls.

The aim of this study was to evaluate the effect of different joint positions, rotator cuff muscle fatigue and experience on shoulder proprioceptive sense among male volleyball players. The participants of the study were 20 experienced (Mage= 20.7 &amp / #61617 / 2.8) and 20 inexperienced (Mage= 17.1 &amp / #61617 / 1.0) male volleyball players being members of first league volleyball teams. Measurements were made by Biodex System 3 pro (Biodex Medical Systems, Inc., New York, USA) and only dominant extremities were assessed. Shoulder proprioceptive sense was determined by measuring participant&rsquo / s perception of joint position sense with the joint at 90&amp / #61616 / abduction, external rotation and 90&amp / #61616 / abduction, neutral rotation. Participants were tested at a speed of 2 deg/s before and after exercising on an isokinetic testing machine until fatigued. Fatigue protocol was practiced at 60 deg/s and it was terminated when the internal rotation maximal peak torque decreased by 50%. There was significant difference between proprioceptive sense of inexperienced volleyball players at 10&amp / #61616 / -20&amp / #61616 / (p&lt / .01) and 15&amp / #61616 / -20&amp / #61616 / (p&lt / .05) in external rotation before fatigue. The difference between before and after fatigue proprioceptive sense of experienced volleyball players at 20&amp / #61616 / (p&lt / .05) was found statistically significant, whereas the significant difference was observed between before and after fatigue proprioceptive sense of inexperienced players at 10&amp / #61616 / (p&lt / .01) and 15&amp / #61616 / (p&lt / .05) in internal rotation. It was concluded that the effect of fatigue on proprioceptive sense is related with experience, but experience itself had no effect on proprioceptive sense.

Thesis (M.S.)--University of Hawaii at Manoa, 2006. / Includes bibliographical references (leaves 55-58). / ix, 58 leaves, bound ill. 29 cm

Thesis (Ph.D.)--Baylor University, 2008. / Includes bibliographical references (p. 131-148).

Thesis (M.S.E.)--Northern Illinois University, 2002. / Includes bibliographical references (leaves [45]-47).