An examination of muscle and tendon properties in children with spastic cerebral palsy and their response to stretch: a theoretical basis for evidence-based clinical practice

This thesis was submitted for the degree of Doctor of Philosophy and awarded by Brunel University.Cerebral palsy (CP) is a heterogeneous disorder in which movement and posture are affected. Increased excitation of the central nervous system leads to neural symptoms, which can cause spasticity and muscle weakness. These neural abnormalities result in secondary CP-related mechanical adaptations of muscles and tendons, which can lead to muscle contracture, joint deformities and pain. Therapeutic interventions are therefore essential to treat CP-induced abnormalities. Passive stretching in particular is a popular treatment method in clinical practice. However, due to a lack of scientific evidence, clinicians often have to make assumptions about the mechanical adaptability of muscles and tendons. Currently, the mechanical properties of muscles and tendons in children with CP and their adaptability are not well understood, which makes it difficult to implement evidence-based practice in clinical settings. Therefore, the overall purpose of this research was to examine the mechanical properties of the medial gastrocnemius muscle and Achilles tendon in children with spastic CP, and the adaptations of the muscle and tendon to acute and long-term passive stretching. The first experimental Chapter (3) was carried out in healthy adults, to assess the agreement between two methods of deriving Achilles tendon stiffness (i) active contraction of the triceps surae muscles to elongate the Achilles tendon, or (ii) passive rotation of the ankle joint. Taking into consideration the tendon’s viscoelastic response, the effects of strain-rate on Achilles tendon stiffness were also described. Results revealed that tendon stiffness measured using the “active method” was 6% greater than the “passive method”. There was also a significant increase in Achilles tendon stiffness in response to increased strain-rate. As the more commonly used active method is problematic to be used in children with CP, due to muscle weakness and excessive co-contraction, the passive method of deriving tendon stiffness was used in subsequent experimental studies. In experimental Chapter 4, differences in the mechanical properties of the Achilles tendon and triceps surae muscles between children with CP and their typically developing (TD) peers, were investigated. The results revealed that estimates of triceps surae muscle stiffness were significantly greater in children with CP compared to TD children. The results also showed that despite a smaller tendon cross-sectional area in children with CP, Achilles tendon stiffness was not different between groups. In addition, children with CP had a steeper tendon stiffness-strain-rate relationship compared to TD children. These results have significant clinical implications regarding the diagnosis of spasticity using the current clinical methods. Experimental Chapters 5 and 6 examined the muscle’s and tendon’s response to stretch. Passive stretching, implemented by a clinician or by the children themselves, is a commonly used intervention for children with CP with the aim of inducing structural alterations in muscles and tendons to improve function. In order for these alterations to take place, elongation of the muscle and fascicles would presumably need to occur with acute stretching. To date, this assumption has not been tested. Thus, the purpose of Chapter 5 was to investigate the medial gastrocnemius and muscle fascicle response to acute stretching, using two commonly used stretch techniques. Results of this study revealed that 100 s of stretching caused a transient increase in tendon (1.0 cm), muscle (0.8 cm) and fascicle lengths (0.6 cm). This effect was independent of stretch technique. These results provide evidence that the muscle and fascicles are capable of elongating in response to stretch in children with spastic CP. They provide a basis for the hypothesis that the spastic muscle may be able to adapt in response to long-term stretching. Thus, the purpose of the final experimental Chapter (6) was to assess the effects of a six week passive stretching intervention (four days per week, 15 minutes per day) on muscle and tendon properties, and gait parameters in children with CP. Results revealed there was a significant reduction in joint stiffness in the experimental group following six weeks of stretching. This was accompanied by a reduction in muscle stiffness, but with no alterations in Achilles tendon stiffness. Additionally, there were no positive effects of passive stretching on gait parameters. Together, the results of the present series of investigations demonstrates how fundamental knowledge of muscle and tendon mechanics in children with spastic CP, can be implemented to support evidence-based clinical practice

Locomotor adaptations during RaceRunning in people with neurological motor disorders

The aim of this study was to examine strategies to absorb impact shock during RaceRunning in participants with neurological motor disorders. For this purpose, eight RaceRunning athletes (four males and four females) voluntarily took part in this study. Each participant performed a series of 100-m sprints with a RaceRunning bike. Acceleration of the tibia and head was measured with two inertial measurement units and used to calculate foot impact shock measures. Results showed that RaceRunning pattern was characterized by a lack of impact peak in foot–ground contact time and the existence of an active peak after foot contact. Due to the ergonomic properties of the RaceRunning bike, shock is attenuated throughout the stance phase. In conclusion, the resultsrevealed that RaceRunning athletes with neurological motor disorders are capable of absorbing impact shock during assisted RaceRunning using a strategy that mimics runners without disabilitie

Concentric versus eccentric training: Effect on muscle strength, regional morphology, and architecture

The different architectural adaptations and the regional changes that occur with eccentric (ECC) vs. concentric (CON) muscle actions are not fully understood. The purpose was to investigate regional changes in vastus lateralis muscle (VL) after ECC and CON training. Sixteen males (23 ± 3 y) performed ECC or CON twice weekly over 5 weeks, using a single-leg design. Both training modalities caused similar increases in knee extensor strength (measured with dynamometry) (10-13%) and muscle volume (8%) (measured with 3D ultrasound) after 5-weeks of training. Anatomical cross-sectional area at the mid-point of the muscle was greater after CON training (9%), but greater at the distal end after ECC training (8%). CON training increased fascicle angle at the mid-point (8%), with little change at the distal end (2%). There was a small increase in fascicle length at the mid-point after CON training (3%). Conversely, ECC training caused a greater variation in regional and architectural adaptations. Fascicle length increased at both the mid-point (6%) and distal ends (8%) after ECC training, and similar changes in fascicle angle were also observed in both regions (3-4%). Different region-specific changes are evident after CON and ECC training, with implications for performance and injury risk

Leucine Supplementation Increases Muscle Strength and Volume, Reduces Inflammation, and Affects Wellbeing in Adults and Adolescents with Cerebral Palsy

BackgroundSpastic cerebral palsy (CP) is characterized by muscle weakness owing, in part, to a blunted muscle protein synthetic response. This might be normalized by long-term leucine supplementation.ObjectivesThe study assessed the effects of 10 wk leucine supplementation in adolescents and adults with CP.MethodsThe study was a single-center randomized controlled trial. Twenty-four participants were randomly assigned to a control group (n = 12) or a leucine group (n = 12). L-Leucine (192 mg/kg body mass) was dissolved in water and administered daily for 10 wk. The primary outcome measures of elbow flexor muscle strength and muscle volume (measured by 3D ultrasound technique) and inflammation [C-reactive protein (CRP) concentration] were assessed before and after the 10 wk, alongside the secondary outcomes of body composition (measured by CP-specific skinfold assessment), metabolic rate (measured by indirect calorimetry), and wellbeing (measured by a self-reported daily questionnaire). Data were compared via a series of 2-factor mixed ANOVAs.ResultsTwenty-one participants completed the intervention (control group: n = 11, mean ± SD age: 18.3 ± 2.8 y, body mass: 48.8 ± 11.9 kg, 45% male; leucine group: n = 10, age: 18.6 ± 1.7 y, body mass: 58.3 ± 20.2 kg, 70% male). After 10 wk, there was a 25.4% increase in strength (P = 0.019) and a 3.6% increase in muscle volume (P = 0.001) in the leucine group, with no changes in the control group. This was accompanied by a 59.1% reduction in CRP (P = 0.045) and improved perceptions of wellbeing (P = 0.006) in the leucine group. No changes in metabolism or body composition were observed in either group (P > 0.05).ConclusionsImprovements in muscle strength and volume with leucine supplementation might provide important functional changes for adults and adolescents with CP and could be partly explained by reduced inflammation. The improved wellbeing highlights its capacity to improve the quality of daily living. This trial was registered at clinicaltrials.gov as NCT03668548

Muscle activation patterns during variable resistance deadlift training with and without elastic bands

The purpose of this study was to determine the effects of band-assisted variable resistance training on muscular activity in the lower limbs and barbell kinematics during the concentric phase of the deadlift. Fifteen resistance trained men (mean ± SD: 28.7 ± 9.3 y; 1.80 ± 0.90 m; 92.5 ± 15.1 kg) performed six deadlift repetitions during four loading conditions; 100 kg bar (NB), 80 kg bar with 20 kg band tension (B20), 75 kg bar with 25 kg band tension (B25) and 70 kg bar with 30 kg band tension (B30). Muscle activity from the medial gastrocnemius (MG), semitendinosus (ST), vastus medialis (VMO), vastus lateralis (VL), and gluteus maximus (GM) were recorded using surface electromyography (sEMG) during the concentric phase of the lift and expressed as a percentage of each muscle’s maximal activity, recorded during a maximal isometric contraction. Barbell power and velocity were recorded using a linear position transducer. Electromyography results showed that muscle activity significantly decreased as band resistance increased in the MG and ST (p < 0.05) and progressively decreased in the GM. No changes were observed for the VMO or VL. Peak and mean bar velocity and power significantly increased as band resistance increased. Performing the deadlift with band-assisted variable resistance increases bar power and velocity, whilst concurrently decreasing muscle activation of the posterior chain musculature. Practitioners prescribing this exercise may wish to include additional posterior chain exercises that have been shown to elicit high levels of muscle activation

Physiological and thermoregulatory effects of oral taurine supplementation on exercise tolerance during forced convective cooling

We investigated the effects of taurine supplementation on cycling time to exhaustion in cold conditions. Eleven males cycled to exhaustion at a power output equivalent to the mid-point between ventilatory threshold and maximum aerobic power following 15-min rest in the cold (apparent temperature of ∼ 4 °C; air flow of 4.17 m·s-1). Two-hours before, participants ingested taurine (50 mg·kg-1) or placebo beverage. Pulmonary gases, carbohydrate (CHO) and fat oxidation, body temperatures, mean local sweat rate, heart rate, rate of perceived exertion (RPE) and thermal comfort were recorded. Time to exhaustion was not different between trials (taurine = 14.6 ± 4.7 min; placebo = 13.4 ± 5.6 min, P = 0.061, d = 0.27). There were no effects (P > 0.05) of taurine on core temperature, mean skin temperature or local sweat rates. However, the placebo condition showed greater (P < 0.05) reductions in arm-to-finger temperature gradient (i.e. vasodilation) across pre-exercise passive cold exposure and increased CHO oxidation (P < 0.05). Participants also reached a thermally ‘comfortable’ level quicker in the taurine condition (P < 0.05). A 50 mg·kg-1 dose of taurine did not statistically benefit endurance exercise after moderate cold exposure but conferred some potential vascular and metabolic effects

Is neuromuscular inhibition detectable in elite footballers during the Nordic hamstring exercise?

The presence of neuromuscular inhibition following injury may explain the high incidence of biceps femoris injury recurrence in elite (soccer) footballers. This phenomenon may be detectable in elite players during the Nordic hamstring exercise. Thus, the first purpose of this study was to assess biceps femoris muscle activation during this exercise in players with hamstring injury history. Additionally, following injury, observed increases in synergistic muscle activation may represent a protective mechanism to the presence of neuromuscular inhibition. Thus, the second purpose was to identify if the relative contributions of biceps femoris, and its synergists reflected a post-injury pattern of activation suggestive of these potentially compensatory neural mechanisms. Ten elite players with a history of hamstring injury and ten elite players without a history of hamstring injury, completed six repetitions of the Nordic hamstring exercise. During each trial, biceps femoris, semitendinosus and gluteus maximus muscle activations were collected at 90-30° and 30-0° of knee flexion. Biceps femoris activation was significantly higher at 90-30° of knee flexion compared to 30-0° (P < 0.001) but did not differ between the groups. In players with a history of injury, muscle activation ratios for the biceps femoris/semitendinosus (P = 0.001) and biceps femoris/gluteus maximus (P = 0.023) were significantly greater at 30-0° of knee flexion than in the control group. Neuromuscular inhibition of the biceps femoris was not detected during the exercise within elite footballers, yet the relative contributions of biceps femoris and its synergists appear to change following injury. [Abstract copyright: Copyright © 2018 Elsevier Ltd. All rights reserved.

Acute effects of neuromuscular electrical stimulation combined with varying degrees of blood flow restriction on muscular, cardiovascular and perceptual variables

Purpose: Recovery from lower limb fracture, surgery or injury often requires a period of immobilisation, which leads to significant declines in muscular strength and size, ranging from 0.3–4.2% per day. A common technique used to attenuate muscle atrophy during immobilisation is neuromuscular electrical stimulation (NMES). However, a more recently utilised intervention is blood flow restriction (BFR). During immobilisation, isolated NMES and BFR have both been shown to reduce muscular atrophy, but not strength declines. Recently, NMES combined with BFR has been investigated and led to increased muscular strength and size in healthy participants and those with spinal cord injuries, compared with NMES and BFR alone. The mechanisms and safety of NMES combined with BFR is currently unknown. The aim of the present study was to discover the acute effects of NMES combined with varying degrees of BFR on muscular, cardiovascular and perceptual variables

No thermoregulatory or ergogenic effect of dietary nitrate among physically inactive males, exercising above gas exchange threshold in hot and dry conditions

The aim of this study was to determine the effect of five days dietary nitrate (NO3-) consumption on exercise tolerance and thermoregulation during cycling in hot, dry conditions. In a double-blind, randomised crossover design, 11 healthy males participated in an exercise tolerance test (Tlim) in the heat (35°C, 28% relative humidity), cycling above the thermoneutral gas exchange threshold, after five days of dietary supplementation, with either NO3--rich beetroot juice (BR; ~ 9.2 mmol NO3-) or placebo (PLA). Changes in plasma [NO3-] and nitrite [NO2-], core and mean skin temperatures, mean local and whole-body sweat rates, heart rate, perceptual ratings and pulmonary gas exchange were measured during exercise, alongside calorimetric estimations of thermal balance. Mean arterial pressures (MAP) were recorded pre-Tlim. There were no differences in Tlim between conditions (BR = 22.8 ± 8.1 min; Placebo = 20.7 ± 7.9 min) (P = 0.184), despite increases in plasma [NO3-] and [NO2-] (P 0.05). Dietary NO3- supplementation had no effect on exercise tolerance or thermoregulation in hot, dry conditions, despite reductions in resting MAP and increases in plasma [NO3-] and [NO2-]. Healthy, yet physically inactive individuals with no known impairments in vasodilatory and sudomotor function do not appear to require BR for ergogenic or thermolytic effects during exercise in the heat

Strength Training for Adolescents with cerebral palsy (STAR): study protocol of a randomised controlled trial to determine the feasibility, acceptability and efficacy of resistance training for adolescents with cerebral palsy

Introduction: Gait is inefficient in children with cerebral palsy, particularly as they transition to adolescence. Gait inefficiency may be associated with declines in gross motor function and participation among adolescents with cerebral palsy. Resistance training may improve gait efficiency through a number of biomechanical and neural mechanisms. The aim of the Strength Training for Adolescents with cerebral palsy (STAR) trial is to evaluate the effect of resistance training on gait efficiency, activity and participation in adolescents with cerebral palsy. We also aim to determine the biomechanical and neural adaptations that occur following resistance training and evaluate the feasibility and acceptability of such an intervention for adolescents with cerebral palsy. Methods and analysis: 60 adolescents (Gross Motor Function Classification System level I–III) will be randomised to a 10-week resistance training group or a usual care control group according to a computer generated random schedule. The primary outcome is gait efficiency. Secondary outcomes are habitual physical activity, participation, muscle–tendon mechanics and gross motor function. General linear models will be used to evaluate differences in continuous data between the resistance training and usual care groups at 10 and 22 weeks, respectively. A process evaluation will be conducted alongside the intervention. Fidelity of the resistance training programme to trial protocol will be quantified by observations of exercise sessions. Semi structured interviews will be conducted with participants and physiotherapists following the resistance training programme to determine feasibility and acceptability of the programme. Ethics and dissemination: This trial has ethical approval from Brunel University London’s Department of Clinical Sciences’ Research Ethics Committee and the National Research Ethics Service (NRES) Committee London—Surrey Borders. The results of the trial will be submitted for publication in academic journals, presented at conferences and distributed to adolescents, families and healthcare professionals through the media with the assistance of the STAR advisory group