The purpose of this study was to compare strength and physical activity (PA) changes in postpartum women randomly assigned to either a four-month progressive resistance training (RT) program or a four month flexibility program. Sixty healthy women between six weeks and eight months postpartum initiated the study and 43 completed the entire study. The women tended to be overweight, were all non-smokers, and most were breastfeeding (97%) at the beginning of the study. Both groups (RT and flexibility) completed training exercises twice weekly. Both groups improved in all measures of strength (RT group: leg press, P < 0.001; bench press, P < 0.001; curl-ups, P < 0.001. Flexibility group: leg press, P = 0.009; bench press, P < 0.001; curl-ups, P = 0.005); however, the RT group had higher strength gains compared to the flexibility group over time (leg press, P < 0.005; bench press, P < 0.001; curl-ups, P < 0.007). In addition, both groups increased in low back flexibility but the group*period interaction did not reach significance (P = 0.096). Light-intensity PA increased in the RT group but not the flexibility group (P < 0.05). A group*period interaction was significant for light-intensity PA time (P = 0.031) and borderline significant for sedentary time (P = 0.054). However, controlling for the number of months postpartum and weight gain during the previous pregnancy resulted in a significant interaction for sedentary time (P < 0.05). No changes were found in moderate, vigorous, or moderate to vigorous PA within or between groups over time. In conclusion, twice-weekly RT increases strength and is associated with improvements in several PA outcomes in postpartum women; however, the mechanisms for this are unclear. The training sessions and/or increased spontaneous activity may have contributed.

The primary purpose of this dissertation was to investigate the effect of training status on adaptations to resistance training. A secondary purpose of this dissertation was to investigate the relationship between subjective and objective forms of monitoring resistance training (RT). The benefits of RT are well understood but training status may be a major influence on training outcomes. Fifteen males of various training status were recruited for this study. Subjects completed 11 weeks of block periodization (BP) training. Subjects were tested for absolute strength (ABS) and relative strength (REL) in the barbell back squat, 0kg and 20kg static jumps (SJ) and 0kg and 20kg countermovement jumps (CMJ). Initial levels of ABS and REL were significantly correlated with rates of improvement for ABS, REL, and SJ and CMJ values. All subjects statistically improved ABS (p

With our global aging population, low muscular strength and function significantly impact an older adult’s capacity to remain independent. Older adults experience gradual declines in physical function and mobility leading to difficulty completing activities of daily living. These difficulties are conceptualized as an expression of mobility disability or through diagnoses of clinical geriatric syndromes such as frailty. Aging physiology in the musculoskeletal system clinically translates into declines in physical function due to losses in muscular strength. Preventative interventions may be appropriate as failing to intervene until critical thresholds are reached will increase healthcare expenditure. Resistance training is a highly beneficial, cost-effective, conservative strategy for community-dwelling older adults to optimize physical resiliency through increasing muscular strength and function lost due to aging, sedentary behaviour and/or physical inactivity. Resistance training needs to be dosed appropriately for function to improve, but clinicians rarely prescribe high-load resistance training with older adults, especially those at risk for mobility decline and frailty. The overarching goal of this thesis was to evaluate the role of resistance training in managing mobility disability and prefrailty. This thesis is comprised of three studies to address this goal: (1) The role of resistance training to improve or prevent mobility disability in community-dwelling older adults: a systematic review and meta-analysis. (2) The use of High- Intensity Enhanced Resistance Training (HEaRT) to optimize independence and quality of life in older adults with or at-risk of mobility disability: a pilot randomized controlled trial. (3) An Ounce of Prevention: a substudy of pre-frail older adults from the HEaRT pilot randomized controlled trial. / Thesis / Candidate in Philosophy / As people get older, the amount of muscle they have, and their strength start to decrease. When too much strength is lost, individuals can begin to have difficulties completing tasks around their home or can be at risk for developing health issues such as disability and frailty. Strength training has been one way proposed to increase strength and physical function for those at risk for mobility disability and those at risk for frailty (prefrailty). This strength training is often of low intensity despite guidelines advocating for higher-intensity exercise. This thesis evaluates the benefit of strength training, specifically using high-load, for those with mobility disability and the safety and feasibility of high-intensity resistance training for those with prefrailty and those at risk for or with established mobility disability.

<p> Resistance exercise training results in skeletal muscle hypertrophy due to accumulated periods ofprotein accretion, the magnitude ofwhich may be influenced by post-exercise feeding. One study suggests that hypertrophy is maximized by immediate provision ofprotein (26); how the type ofprotein ingested in this period affects protein accretion is not known. PURPOSE: To investigate the effect of consuming different post-exercise beverages -milk (MLK), an isonitrogenous and isoenergetic soy drink (PEC), or an isoenergetic control (CON)-on body mass, fat-bone free mass (FBFM), muscle fibre area, and strength during a 12-week progressive whole body resistance training program, in untrained men. METHODS: 34 men were randomized to postexercise consumption ofMLK (n=12; fat free), PEC (n=11; soy) or CON (n=11; maltodextrin) using single-blinded allocation, with characteristics-22.5 ± 0.6 yr, 25.6 ± 0.7 kg/m2• Participants trained 5 d/wk using a whole body split resistance training program and consumed 500 ml oftheir assigned drink immediately and 1h post-exercise following every training bout. RESULTS: Total body mass increased following training (P<0.01) but there were no differences between groups (MLK = 3.2 ± 0.8 kg, PEC = 2.9± 1.4 kg, CON= 2.0 ± 0.8 kg). Similarly, FBFM also increased post-training (P<0.01), but was not different between groups (MLK = 3.3 ± 0.6 kg, PEC = 2.7 ± 0.6kg, CON= 2.2 ± 0.6 kg). Muscle type II fibre area increased post-training (P<0.05) but was not different between groups (MLK = 1004 ± 249 pm2, PEC = 650 ± 192 pm2, CON= 565 ± 120 pm2). Training resulted in increases in 1RM strength for 13 different exercises (P<0.01) with no difference between groups (range= 29-101%). CONCLUSION: Immediate post-exercise provision ofeither milk (MLK), or an isonitrogenous I isoenergetic soy drink (PEC), as well as an isoenergetic carbohydrate beverage (CON), resulted in similar increases in body mass, FBFM, type II muscle fibre area, and strength. This study demonstrates that intact dietary proteins from milk and soy are effective for promoting skeletal muscle hypertrophy. Moreover, when given equivalent energy immediately postexercise, proteins consumed as part of a normal diet, outside ofthe immediate postexercise period are sufficient for hypertrophic and strength gains. Finally, post-exercise consumption ofprotein is no more effective than carbohydrate for promoting skeletal muscle hypertrophy when adequate protein is consumed within a regular diet. </p> / Thesis / Master of Science (MSc)

The mortality/morbidity and quality of life benefits of exercise-based cardiac rehabilitation (CR) are well established, yet adherence to exercise is generally poor post-discharge. Recent trials have attempted to enhance adherence to aerobic activities during transition from CR to home-based exercise. However, these trials have not addressed resistance training, which is also an integral part of many participants' CR exercise routines. Because accessibility to familiar training equipment (e.g., weight machines) and instruction may be limited for many patients upon completion of CR, poor adherence to this beneficial form of exercise can be resultant. The purpose of this study was to examine the effects of a brief intervention involving the provision of a motivation-enhancing instructional manual and elastic Thera-Bands® on self-efficacy for, outcome expectancies for, and adherence to, upper body resistance exercise. It was hypothesized that participants receiving the intervention would report higher self-efficacy, outcome expectancies and greater adherence than those in a standard care control condition. The study was a randomized controlled trial involving informed and consenting CR participants recruited from an established outpatient CR programme at a major urban hospital (N = 40; n_males = 32; M_age= 61.20 ± 11.10). Participants in the intervention group (n=20) received an orientation to home-based upper body resistance training, a theory-based instructional manual designed to enhance self-efficacy and outcome expectations, and Thera-Bands®. The standard care control group received an orientation to home-based upper body resistance training and standard care CR follow-up (n=20). Participants completed baseline measures of self-efficacy for performing resistance training and activities of daily living as well as outcome expectancy measures one week prior to discharge from CR. The same measures were completed again one week later (i.e., at the end of the CR program), and at 4-weeks post-discharge. Participants logged their sets of upper-body resistance exercises continuously throughout the 4-week period following completion of the CR program. There were no differences between groups on any of the study variables at baseline. Participants in the intervention condition reported higher self-efficacy and outcome expectations for resistance training than controls at the 4-week follow-up assessment. Adherence to resistance training was significantly greater with the intervention group completing over twice as many (105%) sets over the four weeks than the control group. Maintaining or increasing upper body strength is an important outcome of CR as it relates to the performance of many activities of daily living. However, adherence to resistance exercises may be difficult upon completion of supervised, facility-based CR. This study illustrates that the provision of a motivation-enhancing instructional manual and low cost materials has a positive impact on self-efficacy, outcome expectations and adherence to resistance training, and may help participants make a successful transition to home-based resistance exercise. / Thesis / Master of Science (MS)

Athletes from an array of sports and military personnel often desire weight gain, ideally as lean body mass (LBM), to improve performance in sport or military operations. These athletic individuals are commonly encouraged to increase energy intake by ~500 kcal/day with an emphasis on adequate protein and carbohydrate (CHO) and judicious inclusion of healthy fat-containing energy-dense foods (including nuts/nut butters), along with rigorous resistance training (RT). These guidelines target gains of ~0.23 kg/wk (0.5 lb/wk). However, little is known about the efficacy of such regimens, particularly in female athletes. Purpose: 1) to evaluate the outcomes of a 10-wk diet and exercise regimen designed to promote healthy weight gain with excess energy from protein- or CHO-dominant foods, 2) to determine the predictors of weight gain under these conditions, and 3) to survey the methods that athletes currently use to achieve weight gain for athletic purposes. Methods: Two projects included 19 male and 13 female athletes (from a variety of athletic backgrounds with previous RT experience; mean age 25±6 years) who were randomly assigned to receive 500 additional kcal/day above weight maintenance diet through provision of either peanut-based whole foods/snacks (PNT group) or a similar, high-CHO, peanut-free snack (CHO group) along with a supervised RT regimen (60 to 120 min, 3 day/wk targeting major muscle groups). Body composition (via dual-energy x-ray absorptiometry), basic anthropometric measurements, resting metabolic rate, hormonal profile, muscular strength, aerobic fitness (VO2max), and food intake records were assessed at baseline (BSL) and post-intervention with some measurements also assessed at weeks 3 and 7. Predictors of weight gain were determined following the intervention. A third project included an online survey with targeted questions regarding athletes' habits for promoting weight gain. Results: 1) Total body mass (TBM) increased 2.2±1.3 kg with 1.5±1.1 kg as LBM after week 10. The PNT group (n=16; 10 men, 6 women) gained less TBM than the CHO group (n=16; 9 men, 7 women) (1.6±1.1 kg vs 2.7±1.2 kg, respectively, P=0.007) with no differences in LBM (1.2±1.1 kg vs 1.9±1.0 kg, P=0.136). 2) 15 (47% women) of 32 participants gained at least 2.27 kg after 10 weeks with 70% as LBM. Over time, from linear mixed effects models, increased free thyroxine (T4) and increased blood urea nitrogen concentration (as a marker of protein intake) predicted TBM and LBM gains. From general linear models, the CHO energy surplus was a significant predictor of TBM and LBM gains, while the female sex alone was significant for LBM gains at study completion. 3) 168 athletic participants (mean age 24±5 years; 29% female, 71% male) completed the survey and were actively attempting or had attempted weight gain in the last 12 months to gain muscle mass (87.5%), for aesthetic reasons (66.1%), or to improve athletic performance (63.7%). The most prevalent dietary strategies reported to help promote weight gain were consuming more energy than usual (88.0%) from mainly protein foods (83.9%) and using protein powders (67.3). 9.6% of participants reported using anabolic hormones. The main exercise change was increased RT (81.5%). Conclusions: 1) These results suggest that the addition of 500 kcal/day from whole foods/snacks in combination with a rigorous RT program promotes a similar weight gain of ~0.22 kg/week, primarily as LBM, over 10 weeks in both male and female athletes. However, snack macronutrient content may impact the effectiveness of this regimen. 2) Factors that predict ability to gain body weight as expected under these circumstances are incorporating a CHO-dominant energy surplus, consuming overall adequate protein (~1.6 g/kg/day), and free T4 status. Furthermore, athletic women are able to gain LBM as effectively as athletic men. 3) Results confirm that both male and female athletic individuals intentionally attempt to gain weight. Nutrition and exercise professionals may use the findings to be aware of these common dietary and exercise strategies and to better educate their athletic clients on appropriate methods that are evidence-based and not detrimental to health. / Doctor of Philosophy / Athletes from different sports, including military members, often want to gain weight, mainly as muscle, to improve their athletic performance (for example, strength and power) or to match the opposing team's size. Current sports nutrition recommendations include eating ~500 kcal more each day from carbohydrate (CHO), protein, and healthy fats in combination with hard weightlifting. These recommendations support a slow weight gain of about 0.5 lb to 1 lb per week, which should mostly be muscle. However, these recommendations have not been well studied, particularly in female athletes. Purpose: 1) to study purposeful overfeeding with weightlifting for 10 weeks to promote healthy weight gain with extra calories from either high-protein or high-CHO foods, 2) to figure out what factors are responsible for healthy weight gain under these conditions, and 3) to survey the methods that athletes currently use to achieve weight gain for athletic purposes. Methods: Two projects included 19 male and 13 female athletes (from a variety of athletic backgrounds with previous weightlifting experience; mean age 25±6 years) who overate 500 additional kcal/day from either peanut-based whole foods/snacks (PNT group) or a similar, high-CHO, peanut-free snack (CHO group) along with a supervised weightlifting regimen (60 to 120 min, 3 day/wk targeting major muscle groups). Body composition, metabolism, blood analyses, muscular strength, cardio fitness, and food intake records were done at the beginning and end with some measurements also done at weeks 3 and 7. Predictors of weight gain were studied later. A third project included an online survey with questions about athletes' habits for promoting weight gain. Results: 1) In all 32 participants, weight increased 4.8 lb (3.3 lb as muscle) after week 10. The PNT group (n=16; 10 men, 6 women) gained less weight than the CHO group (n=16; 9 men, 7 women) (3.5 lb vs 5.9 lb, respectively) with no differences in muscle (2.6 lb vs 4.2 lb). 2) An increased thyroid hormone (thyroxine) and increased blood urea nitrogen (as a marker of protein intake) predicted overall weight and muscle gains. From the beginning of the study, the CHO energy surplus was a significant predictor of weight and muscle gains, while the female sex alone was significant for muscle gains by the end of the study. 3) 168 athletic participants (mean age 24±5 years; 29% female, 71% male) completed the survey and were actively attempting or had attempted weight gain in the last 12 months to gain muscle (87.5%), to look better (66.1%), or to improve athletic performance (63.7%). The main dietary ways reported to help promote weight gain were eating more than usual (88.0%) from mainly protein-rich foods (83.9%) and using protein powders (67.3%). 9.6% of participants reported using anabolic hormones. The main exercise change was increased weightlifting (81.5%). Conclusions: 1) These results suggest that an extra 500 kcal/day from whole foods/snacks in combination with hard weightlifting promotes a similar weight gain of ~0.5 lb/week, mainly as muscle, over 10 weeks in both male and female athletes. 2) What affects healthy weight gain may be eating a CHO-dominant energy surplus, eating enough protein in general, and thyroid status. Furthermore, athletic women are able to gain muscle as effectively as athletic men. 3) Results confirm that both male and female athletic individuals try to gain weight. Nutrition and exercise experts may use these findings to be aware of these common nutrition and exercise strategies and to better educate their athletic clients on appropriate methods that are based on scientific experiments and not bad for health.

It is well documented that engaging in resistance exercise can lead to further improvements in endurance performance. Whilst, not fully understood, it is speculated that increased motor unit recruitment, improved muscle coordination and enhanced utilisation of stored elastic energy after resistance-based exercise improves exercise economy. Nevertheless, while prolonged exposure to resistance training improves endurance performance in the long-term, a consequence of such training when unaccustomed is the appearance of exercise-induced muscle damage (EIMD). Exercise-induced muscle damage is well known to affect athletic performance requiring muscular strength and power; however, its effects on markers of endurance exercise are unclear. Therefore, the aim of this thesis was to investigate the effects of EIMD on endurance performance, with an emphasis on the physiological (oxygen uptake; , minute ventilation; ), metabolic (blood lactate; [La]), perceptual (rating of perceived exertion; RPE) and kinematic (stride length; SL, stride frequency; SF) responses during sub-maximal endurance exercise.

The research presented in this thesis focuses on the development of wireless, real time performance monitoring technology within the resistance training domain using a user-centred design methodology. The functionality of current performance monitoring technology and differences in monitoring ability is investigated through comparative force platform, video and accelerometer testing and analysis. Determining the complexity of resistance training exercises and whether performance variable profiles such as acceleration, velocity and power can be used to characterise lifts is also investigated. A structured user-centred design process suitable for the sporting domain is proposed and followed throughout the research to consider the collection, analysis and communication of performance data. Identifying the user requirements and developing both hardware and software to meet the requirements also forms a major part of the research. The results indicate that as the exercise complexity increases, the requirement for sophisticated technology increases. A simple tri-axial accelerometer can be used to monitor simple linear exercises at the recreational level. Gyroscope technology is required to monitor complex exercises in which rotation of the bar occurs. Force platform technology is required at the elite level to monitor the distribution of force and resultant balance throughout a lift (bilateral difference). An integrated system consisting of an Inertial Measurement Unit (both accelerometer and gyroscope technology) and a double plate force platform is required to accurately monitor performance in the resistance training domain at the elite level.

Dementia is a common cause of disability in the elderly and, in the absence of a successful long-term treatment, it is important to investigate possible lifestyle interventions to help reduce an individual s risk of developing the condition. This thesis investigated the relationship between physical activity and dementia risk, finding that not all research supports the link. The literature review presented in this thesis (Chapter 2) highlighted several possible mediating factors, specifically the type of physical activity performed, the cognitive domains being studied and participant characteristics. Women seemed most susceptible to the effect of physical activity and some other forms of midlife interventions, possible mechanisms for which were discussed in another review (Appendix A). The cognitive test battery to be used in later studies was evaluated for its relevance to dementia and treatment during a 6-month study of Alzheimer's disease patients and their carers (Chapter 3). Memory tasks were found to be especially sensitive to clinical outcomes of dementia treatment (Chapter 4). An observational study of Indonesian elderly found a positive relationship between physical activity and memory performance on the same tests. This effect was strongest in women and in those with no pre-existing cognitive impairment (Chapter 5). However, the relationship could be further modified by other demographic factors, such as education. Health was independently affected in this model by exercise and its association with engaging in physical activity in this cohort was further investigated in Chapter 6. A randomised controlled trial (Chapter 7) was conducted to assess the effect of a 12-week programme of non-aerobic physical activity in sedentary middle-aged adults. Results indicated that resistance training, but not flexibility exercises, influenced memory but not executive function. Overall, this thesis suggests that several types of physical activity may be effective at slowing cognitive decline in elderly groups who are at increased risk of dementia, such as those in middle age and elderly women (Chapter 8). These findings should be expanded with the aim to improve healthcare advice and influence policy-making.

Muscle weakness is one of the major causes of post-stroke disability. Stroke rehabilitation programs now often incorporate the same type of resistance training that is used for healthy subjects; however, the training effects induced from these training strategies are often limited for stroke patients. An important resistance training principle is that an optimal level of stress is exerted on the neuromuscular system, both during concentric (shortening) and eccentric (lengthening) contractions. One potential problem for post-stroke patients might be difficulties achieving sufficient levels of stress on the neuromuscular system. This problem may be associated with altered muscular function after stroke. In healthy subjects, maximum strength during eccentric contractions is higher than during concentric contractions. In individuals with stroke, this difference in strength is often increased. Moreover, it has also been shown that individuals with stroke exhibit alteration with respect to how the strength varies throughout the range of motion. For example, healthy subjects exhibit a joint specific torque-angle relationship that normally is the same irrespective of contraction mode and contraction velocity. In contrast, individuals with stroke exhibit an overall change of the torque-angle relationship. This change, as described in the literature, consists of a more pronounced strength loss at short muscle length. In individuals with stroke, torque-angle relationships are only partially investigated and so far these relationships have not been analysed using testing protocols that include eccentric, isometric, and concentric modes of contraction.   This thesis investigates the torque-angle relationship of elbow flexors in subjects with stroke during all three modes of contractions – isometric, concentric, and eccentric ­– and the relative loading throughout the range of movement during a resistance exercise. In addition, this thesis studies possible central nervous system mechanisms involved in the control of muscle activation during eccentric and concentric contractions.   The torque-angle relationship during maximum voluntary elbow flexion was examined in stroke subjects (n=11), age-matched healthy subjects (n=11), and young subjects (n=11) during different contraction modes and velocities. In stroke subjects, maximum torque as well as the torque angle relationship was better preserved during eccentric contractions compared to concentric contractions. Furthermore, the relative loading during a resistance exercise at an intensity of 10RM (repetition maximum) was examined. Relative loading throughout the concentric phase of the resistance exercise, expressed as percentage of concentric torque, was found to be similar in all groups. However, relative loading during the eccentric contraction phase, expressed as the percentage of eccentric isokinetic torque, was significantly lower for the stroke group. In addition, when related to isometric maximum voluntary contraction, the loading for the stroke group was significantly lower than for the control groups during both the concentric and eccentric contraction phases. Functional magnetic resonance imaging was used to examine differences between recruited brain regions during the concentric and the eccentric phase of imagined maximum resistance exercise of the elbow flexors (motor imagery) in young healthy subjects (n=18) and in a selected sample of individuals with stroke (n=4). The motor and premotor cortex was less activated during imagined maximum eccentric contractions compared to imagined maximum concentric contraction of elbow flexors. Moreover, BA44 in the ventrolateral prefrontal cortex, a brain area that has been shown to be involved in inhibitory control of motor activity, was additionally recruited during eccentric compared to concentric conditions. This pattern was evident only on the contralesional (the intact hemisphere) in some of the stroke subjects. On the ipsilesional hemisphere, the recruitment in ventrolateral prefrontal cortex was similar for both modes of contractions.    Compared to healthy subjects, the stroke subjects exhibited altered muscular function comprising a specific reduction of torque producing capacity and deviant torque-angle relationship during concentric contractions. Therefore, the relative training load during the resistance exercise at a training intensity of 10RM was lower for subjects with stroke. Furthermore, neuroimaging data indicates that the ventrolateral prefrontal cortex may be involved in a mechanism that modulates cortical motor drive differently depending on mode of the contractions. This might partly be responsible for why it is impossible to fully activate a muscle during eccentric contractions. Moreover, among individuals with stroke, a disturbance of this system could also lie behind the lack of contraction mode-specific modulation of muscle activation that has been found in this population. The altered neuromuscular function evident after a stroke means that stroke victims may find it difficult to supply a sufficient level of stress during traditional resistance exercises to promote adaptation by the neuromuscular system. This insufficiency may partially explain why the increase in strength, in response to conventional resistance training, often has been found to be low among subjects with stroke. / Muskelsvaghet är en av orsakerna till funktionshinder efter stroke. I rehabiliteringsprogram för personer som drabbats av stroke förekommer det numera att styrketräning används i syfte att öka muskelstyrkan. Effekten av styrketräning har dock ofta visat sig vara begränsad. En viktig styrketräningsprincip är att muskulaturen belastas tillräckligt nära maximal styrka under både koncentriska kontraktioner (när man lyfter en vikt) och excentriska kontraktioner (när man kontrollerat sänker en vikt). Ett potentiellt problem skulle kunna vara att personer med stroke inte belastas optimalt under träning på grund av förändrad muskelfunktion. Efter stroke är muskelfunktionen ofta förändrad såtillvida att styrkenedsättningen är mer uttalad under koncentriska kontraktioner. Därutöver har man funnit att styrkenedsättningen är mest uttalad när muskeln är i sitt mest förkortade läge. Detta fenomen har dock inte studerats för alla tre kontraktionstyper, det vill säga excentriska, koncentriska och isometriska kontraktioner, hos personer med stroke.   Denna avhandling undersöker sambandet mellan styrka och ledvinkel över armbågsleden hos personer med stroke under alla tre kontraktionstyper – excentrisk, koncentrisk och isometrisk, samt relativ belastning genom rörelsebanan under en styrketräningsövning. Därutöver undersöker denna avhandling också hjärnans aktiveringsmönster under excentriska och koncentriska kontraktioner.   Sambandet mellan styrka och ledvinkel undersöktes hos personer med stroke (n = 11), åldersmatchade (n = 11) och unga försökspersoner (n = 11). Jämfört med kontrollgrupperna var maximal styrka för personer med stroke mest nedsatt, samt även den oproportionerligt stora styrkenedsättningen vid kort muskelängd som mest uttalad, under koncentriska kontraktioner. Denna avvikelse var minst uttalad vid excentriska kontraktioner. Vidare studerades hur hög belastningen på muskulaturen var i jämförelse med muskelns maximala styrka under en styrketräningsliknande övning för armbågsflexorer vid en träningsintensitet på 10RM. Den uppmätta belastningen under den koncentriska fasen av styrketräningsövningen, uttryckt som procent av den genomsnittliga koncentriska styrkan, var densamma för alla grupperna. Under den excentriska fasen av övningen var dock belastningen, uttryckt som procent av den maximala excentriska styrkan, signifikant lägre för personer med stroke. Träningsbelastningen utgjorde också en lägre andel av den maximala isometriska styrkan för personer med stroke, både under den koncentriska och under den excentriska fasen.   Funktionell magnetresonanstomografi (fMRI) användes för att undersöka hjärnans aktiveringsmönster hos unga försökspersoner (n = 18) och hos individer med stroke (n = 4) när de föreställde sig att de utförde maximal styrketräning för armbågsflexorer (motor imagery). Resultatet visade att primära motorbarken och premotoriska barken var mindre aktiverade när unga friska försökspersonerna föreställde sig utföra maximala excentriska, jämfört med maximala koncentriska kontraktioner. Dessutom var en region i ventrolaterala prefrontala barken, som i tidigare studier visat sig vara inblandat i reglering och hämning av muskelaktivering, mer aktiverade under föreställda excentriska kontraktioner. Detta aktiveringsmönster i den prefrontala barken återfanns dock endast i den icke skadade hjärnhalvan hos personer med stroke.   Jämfört med kontrollgrupperna uppvisade försökspersonerna med stroke en förändrad muskelfunktion som bestod av en specifik nedsättning av styrkan under koncentriska kontraktioner samt också ett mer avvikande samband mellan styrka och ledvinkel under koncentriska kontraktioner. Den relativa belastningen under utförandet av en styrketräningsövning med en intensitet på 10RM var på grund av dessa avvikelser lägre för försökspersoner med stroke. Hjärnavbildnings-studierna indikerade att ventrolaterala prefrontala barken verkar vara involverat i ett kortikalt moduleringssystem som reglerar muskel-aktivering olika beroende på kontraktionstyp under maximala kontraktioner. Detta skulle kunna vara en underliggande mekanism bakom den hittills obesvarade frågan varför det är omöjligt att aktivera muskulaturen maximalt under excentriska kontraktioner. En störning av detta moduleringssystem hos personer med stroke verkar också kunna ligga bakom den förändrade regleringen av muskelaktivering som visat sig förekomma hos personer med stroke. Neuromuskulär funktion efter stroke är förändrad i flera avseenden vilket verkar medföra att muskulaturen inte belastas optimalt under konventionell styrketräning. Detta kan vara en delförklaring till varför styrkeökningen som svar på träning ofta är liten hos personer med stroke.