26 results on '"Neale A. Tillin"'
Search Results
2. Heat acclimation reduces the effects of whole-body hyperthermia on knee-extensor relaxation rate, but does not affect voluntary torque production
- Author
-
Ralph Joseph Frederick Hills Gordon, Jodie Natasha Moss, Federico Castelli, Thomas Reeve, Ceri Elen Diss, Christopher James Tyler, and Neale Anthony Tillin
- Subjects
Physiology ,Physiology (medical) ,Public Health, Environmental and Occupational Health ,Orthopedics and Sports Medicine ,General Medicine - Abstract
Purpose This study investigated the effects of acute hyperthermia and heat acclimation (HA) on maximal and rapid voluntary torque production, and their neuromuscular determinants. Methods Ten participants completed 10 days of isothermic HA (50 °C, 50% rh) and had their knee-extensor neuromuscular function assessed in normothermic and hyperthermic conditions, pre-, after 5 and after 10 days of HA. Electrically evoked twitch and octet (300 Hz) contractions were delivered at rest. Maximum voluntary torque (MVT), surface electromyography (EMG) normalised to maximal M-wave, and voluntary activation (VA) were assessed during brief maximal isometric voluntary contractions. Rate of torque development (RTD) and normalised EMG were measured during rapid voluntary contractions. Results Acute hyperthermia reduced neural drive (EMG at MVT and during rapid voluntary contractions; P P P P P Conclusion HA-induced favourable adaptations to the heat after 5 and 10 days of exposure, but there was no measurable benefit on voluntary neuromuscular function in normothermic or hyperthermic conditions. HA did reduce the hyperthermic-induced reduction in twitch half-relaxation time, which may benefit twitch force summation and thus help preserve voluntary torque in hot environmental conditions.
- Published
- 2023
3. The associations between asymmetries in quadriceps strength and gait in individuals with unilateral transtibial amputation
- Author
-
Amy R Sibley, Siobhan Strike, Sarah C. Moudy, and Neale A. Tillin
- Subjects
medicine.medical_specialty ,Rehabilitation ,Vertical ground reaction force ,Biophysics ,Quadriceps strength ,Walking ,Isometric exercise ,Knee extension ,Stride length ,Amputation, Surgical ,Quadriceps Muscle ,Preferred walking speed ,Gait (human) ,Physical medicine and rehabilitation ,Torque ,Transtibial amputation ,medicine ,Humans ,Orthopedics and Sports Medicine ,Gait ,human activities ,Mathematics - Abstract
Background Individuals with unilateral transtibial amputations (ITTAs) are asymmetrical in quadriceps strength. It is unknown if this is associated with gait performance characteristics such as walking speed and limb symmetry. Research question Are quadriceps strength asymmetries related to walking speed and/ or gait asymmetries in ITTAs? Methods Knee-extensor isometric maximum voluntary torque (MVT) and rate of torque development (RTD) were measured in eight ITTAs. Gait data were captured as the ITTAs walked at self-selected habitual and fast speeds. Step length and single support time, peak knee extension moments and their impulse and peak vertical ground reaction force (vGRF) in the braking and propulsive phases of stance were extracted. Bilateral Asymmetry Index (BAI) and, for gait variables only, difference in BAI between walking speeds (ΔBAI) were calculated. Correlation analyses assessed the relationships between MVT and RTD asymmetry and (1) walking speed; (2) gait asymmetries. Results Associations between strength and gait BAIs generally became more apparent at faster walking speeds, and when the difference in BAI between fast and habitual walking speed was considered. BAI RTD was strongly negatively correlated with habitual and fast walking speeds (r=∼0.83). Larger BAI RTD was strongly correlated with propulsive vGRF BAI in fast walking, and larger ΔBAIs in vGRF during both the braking and propulsion phases of gait (r = 0.74–0.92). ITTAs who exhibited greater BAI MVT showed greater ΔBAI in single support time (r = 0.83). Significance While MVT and RTD BAI appear to be associated with gait asymmetries in ITTAs, the magnitude of the asymmetry in RTD appears to be a more sensitive marker of walking speed. Based on these results, it’s possible that strengthening the knee-extensors of the amputated limb to improve both MVT and RTD symmetry may benefit walking speed, and reduce asymmetrical loading in gait.
- Published
- 2021
4. Progressive hyperthermia elicits distinct responses in maximum and rapid torque production
- Author
-
Neale A. Tillin, Ralph Gordon, Christopher J. Tyler, Ceri Diss, and Federico Castelli
- Subjects
Adult ,Male ,Hyperthermia ,medicine.medical_specialty ,Hot Temperature ,Physical Therapy, Sports Therapy and Rehabilitation ,Isometric exercise ,Electromyography ,Young Adult ,03 medical and health sciences ,0302 clinical medicine ,Internal medicine ,Humans ,Torque ,Medicine ,Orthopedics and Sports Medicine ,Muscle Strength ,030212 general & internal medicine ,Muscle, Skeletal ,medicine.diagnostic_test ,business.industry ,Excitation–contraction coupling ,Repeated measures design ,Humidity ,Rectal temperature ,030229 sport sciences ,medicine.disease ,Cardiology ,medicine.symptom ,business ,Body Temperature Regulation ,Muscle Contraction ,Muscle contraction - Abstract
Objectives To investigate the effect of progressive whole-body hyperthermia on maximal, and rapid voluntary torque production, and their neuromuscular determinants. Design Repeated measures, randomised. Methods Nine participants performed sets of neuromuscular assessments in HOT conditions (∼50 °C, ∼35% relative humidity) at rectal temperatures (Tre) of 37, 38.5 and 39.5 °C and in CON conditions (∼22 °C, ∼35% relative humidity) at a Tre of ∼37 °C and pre-determined comparative time-points. Electrically evoked twitch (single impulse) and octet (8 impulses at 300 Hz) responses were measured at rest. Maximum voluntary torque (MVT), surface electromyography (EMG) normalised to maximal M-wave, and voluntary activation (VA) were measured during 3−5 s isometric maximal voluntary contractions. Rate of torque development (RTD) and normalised EMG were measured during rapid voluntary isometric contractions from rest. Results All neuromuscular variables were unaffected by time in CON. In HOT, MVT, normalised EMG at MVT and VA were lower at 39.5 °C compared to 37 °C (p 0.05), despite lower normalised EMG at Tre 39.5 °C (p Conclusions Hyperthermia reduced late-phase voluntary RTD, likely due to reduced neural drive and the reduction in MVT. In contrast, early- and middle-phase voluntary RTD were unaffected by hyperthermia, likely due to the conflicting effects of reduced neural drive but faster intrinsic contractile properties.
- Published
- 2021
5. Muscle quality indices separately associate with joint-level power-related measures of the knee extensors in older males
- Author
-
Kosuke Hirata, Mari Ito, Yuta Nomura, Chiho Kawashima, Yuma Tsuchiya, Kosuke Ooba, Tsukasa Yoshida, Yosuke Yamada, Geoffrey A. Power, Neale A. Tillin, and Ryota Akagi
- Subjects
Male ,Knee Joint ,Physiology ,Public Health, Environmental and Occupational Health ,Water ,General Medicine ,Quadriceps Muscle ,Torque ,Physiology (medical) ,Isometric Contraction ,Humans ,Orthopedics and Sports Medicine ,Knee ,Muscle Strength ,Muscle, Skeletal ,Aged - Abstract
Purpose The purpose of this study was to investigate associations of muscle quality indices with joint-level power-related measures in the knee extensors of thirty-two older males (65–88 years). Methods Muscle quality indices included: echo intensity, ratio of intracellular- to total water content (ICW/TW), and specific muscle strength. Echo intensity was acquired from the rectus femoris (EIRF) and vastus lateralis (EIVL) by ultrasonography. ICW/TW was computed from electrical resistance of the right thigh obtained by bioelectrical impedance spectroscopy. Specific muscle strength was determined as the normalized maximal voluntary isometric knee extension (MVIC) torque to estimated knee extensor volume. Isotonic maximal effort knee extensions with a load set to 20% MVIC torque were performed to obtain the knee extension power-related measures (peak power, rate of power development [RPD], and rate of velocity development [RVD]). Power and RPD were normalized to MVIC. Results There were no significant correlations between muscle quality indices except between EIRF and EIVL (|r|≤ 0.253, P ≥ 0.162). EIRF was negatively correlated with normalized RPD and RVD (r ≤ − 0.361, P ≤ 0.050). ICW/TW was positively correlated with normalized peak power (r = 0.421, P = 0.020). Specific muscle strength was positively correlated with absolute peak power and RPD (r ≥ 0.452, P ≤ 0.012). Conclusion Knee extension power-related measures were lower in participants with higher EI, lower ICW/TW, and lower specific muscle strength, but the muscle quality indices may be determined by independent physiological characteristics.
- Published
- 2022
6. Lead limb loading during a single-step descent in persons with and without a transtibial amputation in the trailing limb
- Author
-
Sarah C. Moudy, Neale A. Tillin, Amy R Sibley, and Siobhan Strike
- Subjects
Adult ,Male ,medicine.medical_specialty ,Biophysics ,Artificial Limbs ,Kinematics ,Walking ,Amputation, Surgical ,Weight-Bearing ,03 medical and health sciences ,0302 clinical medicine ,Physical medicine and rehabilitation ,medicine ,Humans ,Orthopedics and Sports Medicine ,Force platform ,Lead (electronics) ,Limb loading ,Mechanical Phenomena ,Tibia ,business.industry ,Work (physics) ,Biomechanics ,030229 sport sciences ,Biomechanical Phenomena ,body regions ,Kinetics ,medicine.anatomical_structure ,Female ,Descent (aeronautics) ,Ankle ,business ,030217 neurology & neurosurgery - Abstract
Decreased mechanical work done by the trailing limb when descending a single-step could affect load development and increase injury risk on the leading limb. This study assessed the effect of trailing limb mechanics on the development of lead limb load during a step descent by examining individuals with unilateral transtibial amputations who are known to exhibit reduced work in the prosthetic limb.Eight amputees and 10 able-bodied controls walked 5 m along the length of a raised platform, descended a single-step of 14 cm height, and continued walking. The intact limb of amputees led during descent. Kinematic and kinetic data were recorded using integrated motion capture and force platform system. Lead limb loading was assessed through vertical ground reaction force, and knee moments and joint reaction forces. Sagittal-plane joint work was calculated for the ankle, knee, and hip in both limbs.No differences were found in lead limb loading despite differences in trail limb mechanics evidenced by amputees performing 58% less total work by the trailing (prosthetic) limb to lower the centre of mass (P = 0.004) and 111% less for propulsion (P 0.001). Amputees descended the step significantly slower (P = 0.003) and performed significantly greater lead limb ankle work (P = 0.017). After accounting for speed differences, initial loading at the knee was significantly higher in the lead limb of amputees versus controls.Increasing lead limb work and reducing forward velocity may be effective compensatory strategies to limit lead limb loading during a step descent, in response to reduced trailing limb work.
- Published
- 2020
7. The effect of head and neck per-cooling on neuromuscular fatigue following exercise in the heat
- Author
-
Christopher J. Tyler, Ralph Gordon, and Neale A. Tillin
- Subjects
Hyperthermia ,Adult ,Male ,Materials science ,Hot Temperature ,Physiology ,Endocrinology, Diabetes and Metabolism ,Thermal strain ,Protein Serine-Threonine Kinases ,03 medical and health sciences ,Young Adult ,0302 clinical medicine ,Voluntary contraction ,Physiology (medical) ,Isometric Contraction ,medicine ,Humans ,Head and neck ,Exercise ,Nutrition and Dietetics ,Knee extensors ,Electromyography ,Intracellular Signaling Peptides and Proteins ,VO2 max ,030229 sport sciences ,General Medicine ,medicine.disease ,Peripheral ,Cold Temperature ,Neuromuscular fatigue ,Anesthesia ,Muscle Fatigue ,Head ,030217 neurology & neurosurgery - Abstract
The effect of localised head and neck per-cooling on central and peripheral fatigue during high thermal strain was investigated. Fourteen participants cycled for 60 min at 50% peak oxygen uptake on 3 occasions: thermoneutral control (CON; 18 °C), hot (HOT; 35 °C), and HOT with head and neck cooling (HOTcooling). Maximal voluntary force (MVF) and central activation ratio (CAR) of the knee extensors were measured every 30 s during a sustained maximal voluntary contraction (MVC). Triplet peak force was measured following cycling, before and after the MVC. Rectal temperatures were higher in HOTcooling (39.2 ± 0.6 °C) and HOT (39.3 ± 0.5 °C) than CON (38.1 ± 0.3 °C; P < 0.05). Head and neck thermal sensation was similar in HOTcooling (4.2 ± 1.4) and CON (4.4 ± 0.9; P > 0.05) but lower than HOT (5.9 ± 1.5; P < 0.05). MVF and CAR were lower in HOT than CON throughout the MVC (P < 0.05). MVF and CAR were also lower in HOTcooling than CON at 5, 60, and 120 s, but similar at 30 and 90 s into the MVC (P > 0.05). Furthermore, they were greater in HOTcooling than HOT at 30 s, whilst triplet peak force was preserved in HOT after MVC. These results provide evidence that central fatigue following exercise in the heat is partially attenuated with head and neck cooling, which may be at the expense of greater peripheral fatigue. Novelty Central fatigue was greatest during hyperthermia. Head and neck cooling partially attenuated the greater central fatigue in the heat. Per-cooling led to more voluntary force production and more peripheral fatigue.
- Published
- 2020
8. The influence of patellar tendon and muscle-tendon unit stiffness on quadriceps explosive strength in man
- Author
-
Neale A. Tillin, Jonathan P. Folland, Thomas M. Maden-Wilkinson, Garry J. Massey, and Thomas G. Balshaw
- Subjects
musculoskeletal diseases ,Explosive strength ,Stiffness ,030229 sport sciences ,General Medicine ,Isometric exercise ,Anatomy ,musculoskeletal system ,Patellar tendon ,Tendon ,03 medical and health sciences ,0302 clinical medicine ,medicine.anatomical_structure ,medicine ,Torque ,Aponeurosis ,medicine.symptom ,Tissue stiffness ,030217 neurology & neurosurgery ,Biomedical engineering ,Mathematics - Abstract
What is the central question of this study? Do tendon and/or muscle–tendon unit stiffness influence rate of torque development? What is the main finding and its importance? In our experimental conditions, some measures of relative (to maximal voluntary torque and tissue length) muscle–tendon unit stiffness had small correlations with voluntary/evoked rate of torque development over matching torque increments. However, absolute and relative tendon stiffness were unrelated to voluntary and evoked rate of torque development. Therefore, the muscle aponeurosis but not free tendon influences the relative rate of torque development. Factors other than tissue stiffness more strongly determine the absolute rate of torque development. The influence of musculotendinous tissue stiffness on contractile rate of torque development (RTD) remains opaque. In this study, we examined the relationships between both patellar tendon (PT) and vastus lateralis muscle–tendon unit (MTU) stiffness and the voluntary and evoked knee-extension RTD. Fifty-two healthy untrained men completed duplicate laboratory sessions. Absolute and relative RTD were measured at 50 N m or 25% maximal voluntary torque (MVT) increments from onset and sequentially during explosive voluntary and evoked octet isometric contractions (supramaximal stimulation; eight pulses at 300 Hz). Isometric MVT was also assessed. Patellar tendon and MTU stiffness were derived from simultaneous force and ultrasound recordings of the PT and vastus lateralis aponeurosis during constant RTD ramp contractions. Absolute and relative (to MVT and resting tissue length) stiffness (k) was measured over identical torque increments as RTD. Pearson's correlations tested relationships between stiffness and RTD measurements over matching absolute/relative torque increments. Absolute and relative PT k were unrelated to equivalent voluntary/evoked (r = 0.020–0.255, P = 0.069–0.891). Absolute MTU k was unrelated to voluntary or evoked RTD (r ≤ 0.191, P ≥ 0.184), but some measures of relative MTU k were related to relative voluntary/evoked RTD (e.g. RTD for 25–50% MVT, r = 0.374/0.353, P = 0.007/0.014). In conclusion, relative MTU k explained a small proportion of the variance in relative voluntary and evoked RTD (both ≤19%), despite no association of absolute MTU k or absolute/relative PT k with equivalent RTD measures. Therefore, the muscle-aponeurosis component but not free tendon was associated with relative RTD, although it seems that an overriding influence of MVT negated any relationship of absolute MTU k and absolute RTD.
- Published
- 2017
9. The Role of the IGF-1 Signaling Cascade in Muscle Protein Synthesis and Anabolic Resistance in Aging Skeletal Muscle
- Author
-
Neale A. Tillin, Christopher J. Tyler, Nicholas A. Burd, Richard W.A. Mackenzie, and Richie D. Barclay
- Subjects
0301 basic medicine ,medicine.medical_specialty ,Anabolism ,Endocrinology, Diabetes and Metabolism ,medicine.medical_treatment ,lcsh:TX341-641 ,030209 endocrinology & metabolism ,Review ,sarcopenia ,03 medical and health sciences ,Insulin-like growth factor ,0302 clinical medicine ,Insulin resistance ,IP6K1 ,Internal medicine ,Medicine ,Mechanistic target of rapamycin ,Protein kinase B ,Nutrition ,030109 nutrition & dietetics ,Nutrition and Dietetics ,biology ,business.industry ,Akt ,Insulin ,aging ,Skeletal muscle ,medicine.disease ,anabolic resistance ,resistance exercise ,Endocrinology ,medicine.anatomical_structure ,Sarcopenia ,mTOR ,biology.protein ,protein ,business ,lcsh:Nutrition. Foods and food supply ,Food Science - Abstract
Sarcopenia is defined as the combined loss of skeletal muscle strength, function, and/or mass with aging. This degenerative loss of muscle mass is associated with poor quality of life and early mortality humans. The loss of muscle mass occurs due to acute changes in daily muscle net protein balance (NPB). It is generally believed a poor NPB occurs due to reduced muscle protein synthetic responses to exercise, dietary amino acid availability, or an insensitivity of insulin to suppress breakdown. Hence, aging muscles appear to be resistant to the anabolic action of exercise and protein (amino acids or hormonal) when compared to their younger counterparts. The mechanisms that underpin anabolic resistance to anabolic stimuli (protein and resistance exercise) are multifactorial and may be partly driven by poor lifestyle choices (increased sedentary time and reduced dietary protein intake) as well as an inherent dysregulated mechanism in old muscles irrespective of the environmental stimuli. The insulin like growth factor 1 (IGF-1), Akt /Protein Kinase B and mechanistic target of rapamycin (mTOR) pathway is the primary driver between mechanical contraction and protein synthesis and may be a site of dysregulation between old and younger people. Therefore, our review aims to describe and summarize the differences seen in older muscle in this pathway in response to resistance exercise (RE) and describe approaches that researchers have sought out to maximize the response in muscle. Furthermore, this review will present the hypothesis that inositol hexakisphosphate kinase 1 (IP6K1) may be implicated in IGF-1 signaling and thus sarcopenia, based on recent evidence that IGF-1 and insulin share some intracellular bound signaling events and that IP6K1 has been implicated in skeletal muscle insulin resistance.
- Published
- 2019
10. The effects of long-term muscle disuse on neuromuscular function in unilateral transtibial amputees
- Author
-
Sarah C. Moudy, Neale A. Tillin, Siobhan Strike, and Amy R Sibley
- Subjects
Adult ,Male ,medicine.medical_specialty ,Knee Joint ,Physiology ,Population ,Isometric exercise ,030204 cardiovascular system & hematology ,Quadriceps Muscle ,03 medical and health sciences ,Young Adult ,0302 clinical medicine ,Physical medicine and rehabilitation ,Amputees ,Physiology (medical) ,Medicine ,Humans ,Knee ,Muscle Strength ,education ,Quadriceps muscle strength ,education.field_of_study ,Nutrition and Dietetics ,business.industry ,Electromyography ,General Medicine ,Middle Aged ,Gait ,Muscle atrophy ,Kinetics ,Torque ,Gait analysis ,Muscle strength ,medicine.symptom ,business ,Muscle architecture ,030217 neurology & neurosurgery ,Muscle Contraction - Abstract
New findings What is the central question of this study? The effects of long-term muscle disuse on neuromuscular function are unclear because disuse studies are typically short term. In this study, we used a new model (unilateral transtibial amputees) to investigate the effects of long-term disuse on quadriceps neuromuscular function. What is the main finding and its importance? Kinetic analysis (knee-extension moments during gait) indicated habitual disuse of the amputated limb quadriceps, accompanied by lower quadriceps muscle strength (60-76%) and neural activation (32-44%), slower contractile properties and altered muscle architecture in the amputated limb, which could not be predicted from short-term disuse studies. Abstract The purpose of this study was to determine: (i) whether individuals with unilateral transtibial amputations (ITTAs), who habitually disuse the quadriceps muscles of their amputated limb, provide an effective model for assessing the effects of long-term muscle disuse; and (ii) the effects of such disuse on quadriceps muscle strength and neuromuscular function in this population. Nine ITTAs and nine control subjects performed isometric voluntary knee extensions of both limbs to assess maximal voluntary torque (MVT) and the rate of torque development (RTD). The interpolated twitch technique and EMG normalized to maximal M-wave were used to assess neural activation, involuntary (twitch and octet) contractions to assess intrinsic contractile properties, and ultrasound images of the vastus lateralis to assess muscle architecture. Clinical gait analysis was used to measure knee kinetic data during walking at an habitual speed. The ITTAs displayed 54-60% lower peak knee-extensor moments during walking in the amputated compared with intact/control limbs, but the intact and control limbs were comparable for loading during walking and muscle strength variables, suggesting that the intact limb provides a suitable internal control for comparison with the disused amputated limb. The MVT and RTD were ∼60 and ∼75% lower, respectively, in the amputated than intact/control limbs. The differences in MVT appeared to be associated with ∼40 and ∼43% lower muscle thickness and neural activation, respectively, and the differences in RTD appeared to be associated with the decline in MVT coupled with slowing of the intrinsic contractile properties. These results indicate considerable changes in strength and neuromuscular function with long-term disuse that could not be predicted from short-term disuse studies.
- Published
- 2019
11. Foot strike alters ground reaction force and knee load when stepping down during ongoing walking
- Author
-
Amy R Sibley, Sarah C. Moudy, Neale A. Tillin, and Siobhan Strike
- Subjects
musculoskeletal diseases ,Adult ,Male ,medicine.medical_specialty ,Heel ,Knee Joint ,Biophysics ,Walking ,03 medical and health sciences ,0302 clinical medicine ,Physical medicine and rehabilitation ,medicine ,Pressure ,Humans ,Orthopedics and Sports Medicine ,Ground reaction force ,Lead (electronics) ,Joint (geology) ,Gait ,business.industry ,Foot ,Rehabilitation ,Work (physics) ,030229 sport sciences ,Healthy Volunteers ,Biomechanical Phenomena ,body regions ,medicine.anatomical_structure ,Descent (aeronautics) ,Ankle ,business ,human activities ,030217 neurology & neurosurgery ,Ankle Joint - Abstract
Background When stepping down from a raised surface, either a toe or heel contact strategy is performed. Increased vertical momentum is likely to be experienced during a step descent, yet the extent to which these descent strategies influence the development of load at the ground and knee has not been examined. Research Question Does descent strategy influence ground and knee joint loading? Does the contribution from leading and trailing limb joint mechanics differ between descent strategies? Methods Twenty-two healthy male participants (age: 34.0 ± 6.5 years, height: 179 ± 6.3 cm, mass: 83.5 ± 13 kg) walked along a raised platform, stepped down from a 14 cm height utilising either a toe (n = 10) or heel (n = 12) initial contact, and continued walking. Vertical ground reaction forces and knee external adduction and flexor moments were extracted for the duration of the braking phase. Joint work was calculated for the ankle, knee, and hip in both the leading and trailing limbs. Results Waveform analysis of the loading features indicated that a toe-contact strategy resulted in significantly reduced loading rates during early braking (1–32% of the braking phase) and significantly increased magnitude in late braking (55–96% of the braking phase). Individuals performing toe landings completed 33% greater overall work (p = 0.091) in the lead limb and utilised the lead limb ankle joint as the main shock absorber (79% of total lead limb work). Concurrently, the trailing limb performed 29% and 21% less work when lowering the centre of mass and propulsion, respectively, compared to a heel landing. Significance A toe-contact strategy results in reduced limb and knee joint loading rates through greater utilisation of the lead limb ankle joint. A heel-contact strategy, however, can reduce loading during late braking by utilising the functionality of the trailing limb.
- Published
- 2019
12. Mechanisms to Attenuate Load in the Intact Limb of Transtibial Amputees When Performing a Unilateral Drop Landing
- Author
-
Sarah C. Moudy, Amy R Sibley, Siobhan Strike, and Neale A. Tillin
- Subjects
medicine.medical_specialty ,business.industry ,Rehabilitation ,Biophysics ,Prosthetic limb ,Quadriceps strength ,030229 sport sciences ,Isometric exercise ,Negative work ,Knee Joint ,03 medical and health sciences ,0302 clinical medicine ,Work demand ,medicine.anatomical_structure ,Physical medicine and rehabilitation ,Medicine ,Orthopedics and Sports Medicine ,Ankle ,business ,Range of motion ,030217 neurology & neurosurgery - Abstract
Individuals with unilateral transtibial amputations experience greater work demand and loading on the intact limb compared with the prosthetic limb, placing this limb at a greater risk of knee joint degenerative conditions. It is possible that increased loading on the intact side may occur due to strength deficits and joint absorption mechanics. This study investigated the intact limb mechanics utilized to attenuate load, independent of prosthetic limb contributions and requirements for forward progression, which could provide an indication of deficiencies in the intact limb. Amputee and healthy control participants completed 3 unilateral drop landings from a 30-cm drop height. Joint angles at touchdown; range of motion; coupling angles; peak powers; and negative work of the ankle, knee, and hip were extracted together with isometric quadriceps strength measures. No significant differences were found in the load or movement mechanics (P ≥ .31, g ≤ 0.42), despite deficits in isometric maximum (20%) and explosive (25%) strength (P ≤ .13, g ≥ 0.61) in the intact limb. These results demonstrate that, when the influence from the prosthetic limb and task demand are absent, and despite deficits in strength, the intact limb adopts joint mechanics similar to able-bodied controls to attenuate limb loading.
- Published
- 2019
13. Rate of torque development scaled to maximum torque available is velocity dependent
- Author
-
Shaun X.T. Ang, Anthony L. Hessel, and Neale A. Tillin
- Subjects
Knee Joint ,Knee extensors ,Rehabilitation ,Biomedical Engineering ,Biophysics ,Angular velocity ,Mechanics ,Rate of force development ,Torque ,Isometric Contraction ,Muscle strength ,Humans ,Knee ,Orthopedics and Sports Medicine ,Muscle, Skeletal ,Maximum torque ,Muscle Contraction ,Mathematics - Abstract
The influence of angular velocity on rate of torque development (RTD) is unknown, despite the inverse, curvilinear torque-velocity relationship for angle- and velocity-specific maximum available torque (Tmax) being well-established. This study investigated the relationship between angular velocity and RTD scaled to Tmax. In 17 participants, tetanic contractions (100-Hz) of the knee extensors were evoked as the knee was passively extended at different iso-velocities between 0° s−1 and 200° s−1. Each condition consisted of evoking 0.25-s contractions without pre-activation (for measuring RTD) commencing as the knee passed 95° of extension, and 1.25-s contractions with pre-activation (for measuring Tmax), commencing 1 s prior to the knee reaching 95°. Torque at 100 ms after torque onset (T100) and peak RTD (RTDpeak) in the contractions without pre-activation were normalised to Tmax. The torque-velocity relationship for T100 was flat in comparison to an inverse, curvilinear relationship for Tmax, resulting in linear increases in normalised T100 and RTDpeak with increased velocity. Results also showed normalised T100 and RTDpeak were likely overestimated due to shortening-induced force depression (FD) which would be greater in contractions with- than without- pre-activation. However, these effects of FD cannot explain the faster normalised RTD with increased velocity, as the relative difference in work done (a proxy for FD) between contractions with and without pre-activation decreased – and thus the overestimation of normalised RTD metrics likely decreased – with increased velocity. In conclusion, RTD scaled to Tmax increases with increased velocity, which appears to be an intrinsic contractile property independent of the effects of force depression.
- Published
- 2021
14. Contraction speed and type influences rapid utilisation of available muscle force: neural and contractile mechanisms
- Author
-
Jonathan P. Folland, Neale A. Tillin, and Matthew T.G. Pain
- Subjects
Adult ,Male ,Contraction (grammar) ,Explosive material ,Knee Joint ,Physiology ,Acceleration ,Isometric exercise ,Aquatic Science ,Concentric ,Quadriceps Muscle ,03 medical and health sciences ,Young Adult ,0302 clinical medicine ,Eccentric ,Torque ,Humans ,Molecular Biology ,Ecology, Evolution, Behavior and Systematics ,Muscle force ,Physics ,Electromyography ,030229 sport sciences ,Biomechanical Phenomena ,Joint angle ,Insect Science ,Animal Science and Zoology ,030217 neurology & neurosurgery ,Biomedical engineering ,Muscle Contraction - Abstract
This study investigated the influence of contraction speed and type on the human ability to rapidly increase torque and utilise the available maximum voluntary torque (MVT) as well as the neuromuscular mechanisms underpinning any effects. Fifteen young, healthy males completed explosive voluntary knee extensions in five conditions: isometric (ISO), and both concentric and eccentric at two constant accelerations of 500 deg s −2 (CON SLOW and ECC SLOW ) and 2000 deg s −2 (CON FAST and ECC FAST ). Explosive torque and quadriceps EMG were recorded every 25 ms up to 150 ms from their respective onsets and normalised to the available MVT and EMG at MVT, respectively, specific to that joint angle and velocity. Neural efficacy (explosive voluntary:evoked octet torque) was also measured, and torque data were entered into a Hill-type muscle model to estimate muscle performance. Explosive torques normalised to MVT (and normalised muscle forces) were greatest in the concentric followed by the isometric and eccentric conditions, and in the fast compared with slow speeds within the same contraction type (CON FAST >CON SLOW >ISO, and ECC FAST >ECC SLOW ). Normalised explosive-phase EMG and neural efficacy were greatest in concentric conditions, followed by isometric and eccentric conditions, but were similar for fast and slow contractions of the same type. Thus, distinct neuromuscular activation appeared to explain the effect of contraction type but not speed on normalised explosive torque, suggesting the speed effect is an intrinsic contractile property. These results provide novel evidence that the ability to rapidly increase torque/force and utilise the available MVT is influenced by both contraction type and speed, owing to neural and contractile mechanisms, respectively.
- Published
- 2018
15. Nitrate Supplement Benefits Contractile Forces in Fatigued but Not Unfatigued Muscle
- Author
-
Sarah C. Moudy, Kirsty M Nourse, Christopher J. Tyler, and Neale A. Tillin
- Subjects
Adult ,Male ,medicine.medical_specialty ,Physical Therapy, Sports Therapy and Rehabilitation ,Electromyography ,030204 cardiovascular system & hematology ,03 medical and health sciences ,chemistry.chemical_compound ,Young Adult ,0302 clinical medicine ,Nitrate ,Human muscle ,Double-Blind Method ,Internal medicine ,Dietary Nitrate ,medicine ,Humans ,Orthopedics and Sports Medicine ,Muscle, Skeletal ,Nitrites ,Nitrates ,Muscle fatigue ,medicine.diagnostic_test ,business.industry ,Excitation–contraction coupling ,Explosive strength ,030229 sport sciences ,Sports Nutritional Physiological Phenomena ,Endocrinology ,chemistry ,Dietary Supplements ,Muscle Fatigue ,medicine.symptom ,business ,Muscle contraction ,Muscle Contraction - Abstract
Evidence suggests dietary nitrate supplementation enhances low-frequency (≤20 Hz) involuntary, but not voluntary, forces in unfatigued human muscle. We investigated the hypotheses that nitrate supplementation would also attenuate low-frequency fatigue and the loss of explosive voluntary forces in fatigued conditions.In a counterbalanced double-blinded order, 17 male participants completed two experimental trials after 7 d of dietary supplementation with either nitrate-rich (NIT) or nitrate-depleted (PLA) beetroot juice. Each trial consisted of measuring isometric knee extension forces during a series of explosive maximal voluntary contractions (MVC) and involuntary tetanic contractions (at 10, 20 50, and 100 Hz) in unfatigued conditions, followed by a fatigue protocol of 60 MVC and a repeat of the tetanic contractions immediately after the 60 MVC.In unfatigued conditions, there was no effect of NIT on any of the measured dependent variables, including maximal voluntary force, explosive impulse, and tetanic peak forces or peak rate of force developments at any frequency. In contrast, the percentage decline in explosive voluntary impulse from the first to the last 6 MVC in the fatigue protocol was lower in NIT (51.1% ± 13.9%) than in PLA (57.3% ± 12.4%; P = 0.039; d = 0.51). Furthermore, low-frequency fatigue determined via the percentage decline in the 20/50-Hz ratio was attenuated in NIT for tetanic peak force (NIT: 12.3% ± 12.0% vs PLA: 17.0% ± 10.1%; P = 0.110; d = 0.46) and tetanic peak rate force development (NIT: 12.3% ± 10.4% vs PLA: 20.3% ± 9.5%; P = 0.011; d = 0.83).Nitrate supplementation reduced the decline in explosive voluntary forces during a fatiguing protocol and attenuated low-frequency fatigue, likely due to reduced disruption of excitation-contraction coupling. However, contrary to previous findings, nitrate supplementation had no effect on contractile performance in unfatigued conditions.
- Published
- 2018
16. The influence of patellar tendon and muscle-tendon unit stiffness on quadriceps explosive strength in man
- Author
-
Garry J, Massey, Thomas G, Balshaw, Thomas M, Maden-Wilkinson, Neale A, Tillin, and Jonathan P, Folland
- Subjects
Adult ,Male ,Knee Joint ,Electromyography ,Quadriceps Muscle ,Tendons ,Torque ,Patellar Ligament ,Isometric Contraction ,Humans ,Knee ,Muscle Strength ,Muscle, Skeletal ,Muscle Contraction - Abstract
What is the central question of this study? Do tendon and/or muscle-tendon unit stiffness influence rate of torque development? What is the main finding and its importance? In our experimental conditions, some measures of relative (to maximal voluntary torque and tissue length) muscle-tendon unit stiffness had small correlations with voluntary/evoked rate of torque development over matching torque increments. However, absolute and relative tendon stiffness were unrelated to voluntary and evoked rate of torque development. Therefore, the muscle aponeurosis but not free tendon influences the relative rate of torque development. Factors other than tissue stiffness more strongly determine the absolute rate of torque development. The influence of musculotendinous tissue stiffness on contractile rate of torque development (RTD) remains opaque. In this study, we examined the relationships between both patellar tendon (PT) and vastus lateralis muscle-tendon unit (MTU) stiffness and the voluntary and evoked knee-extension RTD. Fifty-two healthy untrained men completed duplicate laboratory sessions. Absolute and relative RTD were measured at 50 N m or 25% maximal voluntary torque (MVT) increments from onset and sequentially during explosive voluntary and evoked octet isometric contractions (supramaximal stimulation; eight pulses at 300 Hz). Isometric MVT was also assessed. Patellar tendon and MTU stiffness were derived from simultaneous force and ultrasound recordings of the PT and vastus lateralis aponeurosis during constant RTD ramp contractions. Absolute and relative (to MVT and resting tissue length) stiffness (k) was measured over identical torque increments as RTD. Pearson's correlations tested relationships between stiffness and RTD measurements over matching absolute/relative torque increments. Absolute and relative PT k were unrelated to equivalent voluntary/evoked (r = 0.020-0.255, P = 0.069-0.891). Absolute MTU k was unrelated to voluntary or evoked RTD (r ≤ 0.191, P ≥ 0.184), but some measures of relative MTU k were related to relative voluntary/evoked RTD (e.g. RTD for 25-50% MVT, r = 0.374/0.353, P = 0.007/0.014). In conclusion, relative MTU k explained a small proportion of the variance in relative voluntary and evoked RTD (both ≤19%), despite no association of absolute MTU k or absolute/relative PT k with equivalent RTD measures. Therefore, the muscle-aponeurosis component but not free tendon was associated with relative RTD, although it seems that an overriding influence of MVT negated any relationship of absolute MTU k and absolute RTD.
- Published
- 2016
17. Identification of contraction onset during explosive contractions. Response to Thompson et al. 'Consistency of rapid muscle force characteristics: Influence of muscle contraction onset detection methodology' [J Electromyogr Kinesiol 2012;22(6):893–900]
- Author
-
Jonathan P. Folland, Neale A. Tillin, and Matthew T.G. Pain
- Subjects
Male ,Contraction (grammar) ,Explosive material ,business.industry ,Biophysics ,Neuroscience (miscellaneous) ,Signal Processing, Computer-Assisted ,Anatomy ,Muscle strength ,Humans ,Medicine ,Muscle Strength ,Neurology (clinical) ,medicine.symptom ,Muscle, Skeletal ,business ,Muscle Contraction ,Muscle contraction ,Muscle force - Published
- 2013
18. Explosive force production during isometric squats correlates with athletic performance in rugby union players
- Author
-
Neale A. Tillin, Matthew T.G. Pain, and Jonathan P. Folland
- Subjects
Adult ,Male ,medicine.medical_specialty ,Weight Lifting ,Acceleration ,Physical Exertion ,Explosive force ,Explosive strength ,Physical Therapy, Sports Therapy and Rehabilitation ,Isometric exercise ,Athletic Performance ,Weight lifting ,Running ,Young Adult ,Physical medicine and rehabilitation ,Sprint ,Jump ,Countermovement jump ,medicine ,Humans ,Orthopedics and Sports Medicine ,Muscle Strength ,Early phase ,Simulation ,Mathematics - Abstract
This study investigated the association between explosive force production during isometric squats and athletic performance (sprint time and countermovement jump height). Sprint time (5 and 20 m) and jump height were recorded in 18 male elite-standard varsity rugby union players. Participants also completed a series of maximal- and explosive-isometric squats to measure maximal force and explosive force at 50-ms intervals up to 250 ms from force onset. Sprint performance was related to early phase (≤100 ms) explosive force normalised to maximal force (5 m, r = -0.63, P = 0.005; and 20 m, r = -0.54, P = 0.020), but jump height was related to later phase (100 ms) absolute explosive force (0.51r0.61; 0.006P0.035). When participants were separated for 5-m sprint time (or ≥ 1s), the faster group had greater normalised explosive force in the first 150 ms of explosive-isometric squats (33-67%; 0.001P0.017). The results suggest that explosive force production during isometric squats was associated with athletic performance. Specifically, sprint performance was most strongly related to the proportion of maximal force achieved in the initial phase of explosive-isometric squats, whilst jump height was most strongly related to absolute force in the later phase of the explosive-isometric squats.
- Published
- 2013
19. Short-term training for explosive strength causes neural and mechanical adaptations
- Author
-
Neale A. Tillin, Jonathan P. Folland, and Matthew T.G. Pain
- Subjects
medicine.medical_specialty ,Physical medicine and rehabilitation ,Knee extensors ,business.industry ,Explosive force ,medicine ,Resistance training ,Explosive strength ,General Medicine ,Isometric exercise ,Ultrasonography ,business - Abstract
This study investigated the neural and peripheral adaptations to short-term training for explosive force production. Ten men trained the knee extensors with unilateral explosive isometric contractions (1 s 'fast and hard') for 4 weeks. Before and after training, force was recorded at 50-ms intervals from force onset (F(50), F(100) and F(150)) during both voluntary and involuntary (supramaximal evoked octet; eight pulses at 300 Hz) explosive isometric contractions. Neural drive during the explosive voluntary contractions was measured with the ratio of voluntary/octet force, and average EMG normalized to the peak-to-peak M-wave of the three superficial quadriceps. Maximal voluntary force (MVF) was also measured, and ultrasonic images of the vastus lateralis were recorded during ramped contractions to assess muscle-tendon unit stiffness between 50 and 90% MVF. There was an increase in voluntary F(50) (+54%), F(100) (+15%) and F(150) (+14%) and in octet F(50) (+7%) and F(100) (+10%). Voluntary F(100) and F(150), and octet F(50) and F(100) increased proportionally with MVF (+11%). However, the increase in voluntary F(50) was +37% even after normalization to MVF, and coincided with a 42% increase in both voluntary/octet force and agonist-normalized EMG over the first 50 ms. Muscle-tendon unit stiffness between 50 and 90% MVF also increased. In conclusion, enhanced agonist neural drive and MVF accounted for improved explosive voluntary force production in the early and late phases of the contraction, respectively. The increases in explosive octet force and muscle-tendon unit stiffness provide novel evidence of peripheral adaptations within merely 4 weeks of training for explosive force production.
- Published
- 2012
20. Short-term unilateral resistance training affects the agonist-antagonist but not the force-agonist activation relationship
- Author
-
Neale A. Tillin, Matthew T.G. Pain, and Jonathan P. Folland
- Subjects
Agonist ,medicine.medical_specialty ,medicine.diagnostic_test ,Physiology ,medicine.drug_class ,Agonist–antagonist ,business.industry ,Antagonist ,Resistance training ,Isometric exercise ,Electromyography ,musculoskeletal system ,Coactivation ,body regions ,Cellular and Molecular Neuroscience ,Physiology (medical) ,Internal medicine ,medicine ,Physical therapy ,Cardiology ,Neurology (clinical) ,business ,Knee flexor - Abstract
In this study we investigated the contribution of neural adaptations to strength changes after 4 weeks of unilateral isometric resistance training. Maximal and submaximal isometric knee extension contractions were assessed before and after training. Surface electromyography (EMG) data were collected from the agonist and antagonist muscles and normalized to evoked maximal M-wave and maximal knee flexor EMG, respectively. The interpolated twitch technique (ITT) was also used to determine activation at maximum voluntary force (MVF). MVF increased in the trained (+20%) and untrained (+8%) legs. Agonist EMG at MVF increased in the trained leg (+26%), although activation determined via the ITT was unchanged. In both legs the position of the force-agonist EMG relationship was unchanged, but antagonist coactivation was lower for all levels of agonist activation. Strength gains in the trained leg were due to enhanced agonist activation, whereas decreased coactivation may have affected strength changes in both legs.
- Published
- 2011
21. Neuromuscular Performance of Explosive Power Athletes versus Untrained Individuals
- Author
-
Neale A. Tillin, Pedro Jiménez-Reyes, Matthew T.G. Pain, and Jonathan P. Folland
- Subjects
Male ,medicine.medical_specialty ,Adolescent ,Explosive material ,Physical Therapy, Sports Therapy and Rehabilitation ,Electromyography ,Isometric exercise ,Athletic Performance ,Knee extension ,Quadriceps Muscle ,Young Adult ,Physical medicine and rehabilitation ,Rate of force development ,Time windows ,Humans ,Medicine ,Orthopedics and Sports Medicine ,Neurons ,biology ,medicine.diagnostic_test ,business.industry ,Athletes ,biology.organism_classification ,Physical therapy ,business ,Muscle Contraction ,Explosive power - Abstract
Purpose: Electromechanical delay (EMD) and rate of force development (RFD) are determinants of explosive neuromuscular performance. We may expect a contrast in EMD and RFD between explosive power athletes, who have a demonstrable ability for explosive contractions, and untrained individuals. However, this comparison, and the neuromuscular mechanisms for any differences, has not been studied. Methods: The neuromuscular performance of explosive power athletes (n = 9) and untrained controls (n = 10) was assessed during a series of twitch, tetanic, explosive and maximum voluntary, isometric knee extensions. Knee extension force and EMG of the superficial quadriceps was measured in three 50 ms time windows from their onset, and normalised to strength and maximal M-wave (Mmax), respectively. Involuntary and voluntary EMD were determined from twitch and explosive voluntary contractions, respectively, and were similar for both groups. Results: The athletes were 28% stronger and their absolute RFD in the first 50 ms was 2-fold that of controls. Athletes had greater normalised RFD (4.86 ± 1.46 vs. 2.81 ± 1.20 MVC.s -1 ) and neural activation (mean quadriceps, 0.26 ± 0.07 vs. 0.15 ± 0.06 Mmax) during the first 50 ms of explosive voluntary contractions. Surprisingly the controls had a greater normalised RFD in the second 50 ms (6.68 ± 0.92 vs. 7.93 ± 1.11 MVC.s -1 ) and a greater change in EMG preceding this period. However, there were no differences in the twitch response or normalised tetanic RFD between groups. Conclusion: The differences in voluntary normalised RFD between athletes and controls were explained by agonist muscle neural activation, and not the similar intrinsic contractile properties of the groups.
- Published
- 2010
22. Factors Modulating Post-Activation Potentiation and its Effect on Performance of Subsequent Explosive Activities
- Author
-
Neale A. Tillin and David Bishop
- Subjects
medicine.medical_specialty ,Physical Exertion ,Physical Therapy, Sports Therapy and Rehabilitation ,Athletic Performance ,Stimulus (physiology) ,Humans ,Medicine ,Orthopedics and Sports Medicine ,Muscle Strength ,Fatigue ,business.industry ,Long-term potentiation ,Biomechanical Phenomena ,Motor unit ,Complex training ,Sprint ,Turnover ,Muscle Fibers, Fast-Twitch ,Physical therapy ,Conditioning ,medicine.symptom ,business ,Neuroscience ,Psychomotor Performance ,Muscle Contraction ,Muscle contraction - Abstract
Post-activation potentiation (PAP) is induced by a voluntary conditioning contraction (CC), performed typically at a maximal or near-maximal intensity, and has consistently been shown to increase both peak force and rate of force development during subsequent twitch contractions. The proposed mechanisms underlying PAP are associated with phosphorylation of myosin regulatory light chains, increased recruitment of higher order motor units, and a possible change in pennation angle. If PAP could be induced by a CC in humans, and utilized during a subsequent explosive activity (e.g. jump or sprint), it could potentially enhance mechanical power and thus performance and/or the training stimulus of that activity. However, the CC might also induce fatigue, and it is the balance between PAP and fatigue that will determine the net effect on performance of a subsequent explosive activity. The PAP-fatigue relationship is affected by several variables including CC volume and intensity, recovery period following the CC, type of CC, type of subsequent activity, and subject characteristics. These variables have not been standardized across past research, and as a result, evidence of the effects of CC on performance of subsequent explosive activities is equivocal. In order to better inform and direct future research on this topic, this article will highlight and discuss the key variables that may be responsible for the contrasting results observed in the current literature. Future research should aim to better understand the effect of different conditions on the interaction between PAP and fatigue, with an aim of establishing the specific application (if any) of PAP to sport.
- Published
- 2009
23. Twelve Weeks Of Explosive Strength Training Increases Both Maximal And Explosive Voluntary Torque Production
- Author
-
Neale A. Tillin, Jonathan P. Folland, Garry J. Massey, Thomas M. Maden-Wilkinson, and Thomas G. Balshaw
- Subjects
Aeronautics ,Explosive material ,Training (meteorology) ,Explosive strength ,Environmental science ,Production (economics) ,Torque ,Physical Therapy, Sports Therapy and Rehabilitation ,Orthopedics and Sports Medicine - Published
- 2016
24. Short-term training for explosive strength causes neural and mechanical adaptations
- Author
-
Neale A, Tillin, Matthew T G, Pain, and Jonathan P, Folland
- Subjects
Male ,Tendons ,Young Adult ,Electromyography ,Isometric Contraction ,Humans ,Resistance Training ,Muscle, Skeletal ,Adaptation, Physiological ,Muscle Contraction ,Ultrasonography - Abstract
This study investigated the neural and peripheral adaptations to short-term training for explosive force production. Ten men trained the knee extensors with unilateral explosive isometric contractions (1 s 'fast and hard') for 4 weeks. Before and after training, force was recorded at 50-ms intervals from force onset (F(50), F(100) and F(150)) during both voluntary and involuntary (supramaximal evoked octet; eight pulses at 300 Hz) explosive isometric contractions. Neural drive during the explosive voluntary contractions was measured with the ratio of voluntary/octet force, and average EMG normalized to the peak-to-peak M-wave of the three superficial quadriceps. Maximal voluntary force (MVF) was also measured, and ultrasonic images of the vastus lateralis were recorded during ramped contractions to assess muscle-tendon unit stiffness between 50 and 90% MVF. There was an increase in voluntary F(50) (+54%), F(100) (+15%) and F(150) (+14%) and in octet F(50) (+7%) and F(100) (+10%). Voluntary F(100) and F(150), and octet F(50) and F(100) increased proportionally with MVF (+11%). However, the increase in voluntary F(50) was +37% even after normalization to MVF, and coincided with a 42% increase in both voluntary/octet force and agonist-normalized EMG over the first 50 ms. Muscle-tendon unit stiffness between 50 and 90% MVF also increased. In conclusion, enhanced agonist neural drive and MVF accounted for improved explosive voluntary force production in the early and late phases of the contraction, respectively. The increases in explosive octet force and muscle-tendon unit stiffness provide novel evidence of peripheral adaptations within merely 4 weeks of training for explosive force production.
- Published
- 2012
25. Short-term training for explosive strength causes neural and mechanical adaptations
- Author
-
Neale A. Tillin, Matthew T. G. Pain, and Jonathan P. Folland
- Subjects
General Medicine - Published
- 2012
26. Short-term unilateral resistance training affects the agonist-antagonist but not the force-agonist activation relationship
- Author
-
Neale A, Tillin, Matthew T G, Pain, and Jonathan P, Folland
- Subjects
Male ,Young Adult ,Time Factors ,Electromyography ,Isometric Contraction ,Humans ,Resistance Training ,Muscle Strength ,Electric Stimulation - Abstract
In this study we investigated the contribution of neural adaptations to strength changes after 4 weeks of unilateral isometric resistance training. Maximal and submaximal isometric knee extension contractions were assessed before and after training. Surface electromyography (EMG) data were collected from the agonist and antagonist muscles and normalized to evoked maximal M-wave and maximal knee flexor EMG, respectively. The interpolated twitch technique (ITT) was also used to determine activation at maximum voluntary force (MVF). MVF increased in the trained (+20%) and untrained (+8%) legs. Agonist EMG at MVF increased in the trained leg (+26%), although activation determined via the ITT was unchanged. In both legs the position of the force-agonist EMG relationship was unchanged, but antagonist coactivation was lower for all levels of agonist activation. Strength gains in the trained leg were due to enhanced agonist activation, whereas decreased coactivation may have affected strength changes in both legs.
- Published
- 2011
Catalog
Discovery Service for Jio Institute Digital Library
For full access to our library's resources, please sign in.