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Sammanfattning:  Introduktion: Hamstringsskada är en av de vanligast förekommande skadorna inom fotboll, med betydande konsekvenser för individen. Hamstringsskador har visat sig svåra att rehabilitera. En riskfaktor bland många andra är nedsatt rörlighet i hamstrings. Studier har också visat att det finns samband mellan skador i nedre extremitet, däribland hamstringsskador, och nedsatt funktion i gluteus maximus (GM). Det finns teorier om att belastningen på hamstrings kan minska genom ökad användning av GM och att detta i förlängningen kan leda till minskad styvhet i hamstrings. Syfte: Att undersöka om träning av GM kunde påverka relativ styvhet i hamstrings mätt vid passivt rakt benlyft (PSLR) till dess att medrörelse i bäckenet uppstod, hos manliga fotbollsspelare, jämfört med en kontrollgrupp.  Metod: En prospektiv interventionsstudie med kontrollgrupp där interventionsgruppen under åtta veckor utförde övningar för att öka aktivitet och styrka i GM. Kontrollgruppen utförde bålövningar under samma tidsperiod. Utfall mättes i PSLR med EasyAngle goniometer före och efter intervention. En ANCOVA utfördes för att jämföra utfall mellan grupperna med baslinjemätningen som kovariat.  Resultat: I interventionsgruppen (n=14) ökade medelvärdet med 10° mellan mättillfällena. I kontrollgruppen (n=18) ökade medelvärdet med 2.9°. ANCOVAn visade en statistiskt signifikant skillnad (p <0.002) i den relativa styvheten i hamstrings mellan interventions- och kontrollgrupp efter avslutad intervention. Slutsats: Resultaten indikerar att träning av GM tycks kunna påverka relativ styvhet i hamstrings, även om resultatet ska tolkas med försiktighet utifrån studiens upplägg och storlek. Fler studier med interventioner som studerar effekter av träning av hamstrings synergister behövs.

The broad aim of this thesis was to progress understanding of the neuromechanics of joint stability and injury mechanisms by investigating the interactions between neuromuscular function and balance perturbations as well as the influence of sex and fatigue on these variables. Knee extensor (KE) and plantar flexor (PF) isometric strength parameters (maximum voluntary torque (MVT), explosive voluntary torque (EVT)) were related in young healthy adults. EVT of KE and PF were correlated at 4/5 time points during the rising torque-time curve for all absolute (r = 0.488-0.755) and relative (to body mass (BM) (r = 0.517-0.669) and MVT (r = 0.353-0.480)) expressions of EVT. These results suggest that KE and PF function is related for both maximum and explosive torque. Males were stronger for KE (+89%) and PF (+55%) than females. Males also displayed greater EVT at all time points in KE (+57-109%) and at 50-150 ms in PF (+33-52%). When MVT and EVT were normalised to BM, males continued to be stronger at all time points in KE (+23-60%) and from 100-150 ms (18-20%) in PF. No sex differences were found when EVT was normalised to MVT. Furthermore, sex differences were discovered in muscle morphology. Females had a smaller knee flexor (KF):KE size ratio, a proportionately small sartorius (SA) and gracilis (GR) and a proportionately larger vastus lateralis (VL), potentially predisposing females to greater risk of ACL injury. Females had a larger biceps femoris long head (BFlh) as a proportion of the KF than males, which may contribute to the higher risk of hamstring strain injury (HSI) in males. Regarding explosive performance and perturbation response, explosive PF torque had a weak to moderate correlation with COM displacement (COMD) from 400-500 ms (r = -0.346 to -0.508) and COM velocity (COMV) from 300-500 ms (r = -0.349 to -0.416), with weaker correlations between explosive KE torque and COMV at 400 ms (r = -0.381 to -0.411) but not with COMD. These findings suggest that greater explosive torque results in better control of the COM in response to unexpected perturbations. The effects of football simulated fatigue on these factors resulted in reduced maximal KF and KE torque. However, football simulated fatigue was not found to reduce EVT of either muscle group, or explosive H/Q ratio. Football simulated fatigue resulted in impaired balance response to unexpected perturbation in the posterior but not the anterior direction.

The aim of this study was to investigate the relationship between thigh intramuscular fat (intraMF) and intermuscular fat (IMF) with quadriceps and hamstrings power and physical performance in women (n=20) with clinical, radiographic knee osteoarthritis (OA). Secondarily, we investigated the correlation between thigh and calf fat volumes, and the agreement between 3.0T and 1.0T MRI for quantifying fat. The thigh and calf of the symptomatic leg were scanned using 3.0T MRI with the IDEAL sequence, and fat separated images were analyzed using semi-automated software to quantify intraMF, IMF and muscle. The calf was also scanned using 1.0T MRI with a Fast Spin Echo (FSE) sequence. Knee extensor and flexor isokinetic power was measured at 20% and 40% of individuals’ maximum voluntary isometric contraction (MVIC) torque, and surface electromyography (EMG) measured activation. We found no relationship between quadriceps or hamstrings intraMF and knee extensor or flexor power, respectively. In addition, there were no relationships between intraMF and performance-based tests. There was a correlation between thigh and calf intraMF (r=0.759; p=0.001) and a trend toward a correlation in IMF (r=0.436; p=0.055). There was agreement and a correlation between calf intraMF (r=0.779; p=0.001) and IMF (r=0.956; p=0.001) using 3.0T and 1.0T MRI. There is disagreement about the relationship of intraMF and quadriceps strength, although studies have found that intraMF is related to decreased physical performance. The importance of calf fat subsets in physical performance of individuals with OA should be further investigated. Power analysis demonstrated a sample size (n=91) is recommended for future investigations of intraMF and power in OA. / Thesis / Master of Science in Medical Sciences (MSMS)

Background: Foam rolling (FR) is a promising new trend in the world of resistance training, sports and  athletics. It is often used as a warm up activity as a substitute or addition to  stretching modalities such as static stretching (SS). The proposed benefits behind FR is that it can lead to  both acute and chronic increases in performance and flexibility. Aim: The aim of this study was to investigate the effects of two different warm­up intervention protocols  of the hamstrings musculature on: 1) Performance in the bilateral standing long jump 2) Flexibility in a  supine active­knee­extension test. Method: The study consisted of sixteen male participants who were all healthy adult recreational athletes.  The two different interventions were, a) Static Stretching protocol (SS) and b) a Foam Rolling protocol  (FR). These were compared to a baseline warm up (BLWU). The SS consisted of 1 x 30 seconds of active  SS using the lying supine active­knee­extension position after a short warm­up. The FR consisted of 1  bout of 30 seconds of FR of the hamstrings musculature of each leg after a short warm­up. BLWU  consisted of a short warm­up (5 submaximal bilateral standing long jumps). Performance was measured  using a bilateral standing long jump test. Flexibility was measured with a goniometer using a lying supine active ­knee­ extension test. The student’s t­test was used to study differences between and within groups (BLWU, SS, FR). Results: No differences between BLWU and Post­SS (p=0.89) as well as BLWU compared to Post­FR (p=0.86) was detected for performance. However, an increase in flexibility was shown favoring Post­SS over BLWU (p=0.021) as well as Post­FR over BLWU (p=0.045). No significant difference was seen  between changes in the Post­SS and Post­FR groups in either performance or flexibility (p=0.887 and  p=0.944 respectively). Conclusion: It seems that both SS and FR are similarly viable and effective methods for acute increases  in flexibility in the active­knee­extension test without subsequent decreases in performance of the bilateral standing long jump.

Performance of a series of eccentric contractions produces adverse effects including muscle weakness, delayed onset muscle soreness (DOMS), fluid accumulation and decreased muscle function. The repeated bout effect is a physiological adaptation observed when a single-bout of eccentric exercise protects against muscle damage from subsequent eccentric bouts. Similar to the repeated bout effect, increases in flexibility have been linked to attenuations in acute muscle damage, muscle fatigue and strength loss after eccentric exercise. Purpose: The purpose of this study was to examine the muscle physiological responses to eccentric strength training after first priming the muscles with either a period of static flexibility training or a single intense bout of eccentric exercise performed weeks earlier; and compare these to the responses from eccentric strength training when no prior intervention is administered. Methods: Twenty-five participants were randomly assigned to a flexibility (F) (n=8), a single-bout (SB) (n=9), or a control (C) (n=8) group. The design consisted of two 4-week phases; 1) priming intervention, 2) eccentric training. The priming intervention included static stretching (3x/week; 30mins/day) (F), a single-bout of eccentric exercise (SB) or no priming intervention (C). All groups proceeded to complete eccentric training of the knee flexors using isotonic contractions (%load progressively increased over training period) on a dynamometer following the priming intervention phase. Testing was completed at baseline, post-priming intervention and post-eccentric training, in conjunction with data being collected during the acute eccentric training phase (0hr, 24hr, 48hr; post-bout 1 and 4). Dependent measures included muscle thickness, isometric maximal voluntary contraction (MVC), eccentric and concentric MVC, optimal angle, active range of motion (ROM), passive ROM, maximal power, electromyography (EMG) and delayed onset muscle soreness (DOMS). Results: Acute data during the eccentric training phase revealed a significant reduction in DOMS for both the F and SB groups compared to the C following the first bout of eccentric exercise (p<0.05). The F also had reduced soreness in comparison to both the SB and C post fourth bout of eccentric exercise (p<0.05). The F group demonstrated attenuated loss in isometric strength (post fourth bout) and maximal power (post first bout) during eccentric training compared to the C group (p<0.05). However, there was no significant difference between groups across all dependent variables following the eccentric training phase. Conclusion: This is the first study to directly compare the protective effects observed with static flexibility training to that of a single-bout of eccentric exercise throughout a subsequent eccentric training regime. Although differences in muscle soreness, strength and maximal power occurred during the acute stages of eccentric training, there appeared to be no significant advantage of either protective priming method at the end of eccentric training.

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名古屋大学博士学位論文 学位の種類 : 博士(医学)(論文) 学位授与年月日:平成4年3月25日 井戸田仁氏の博士論文として提出された