Science & Technogym
Research & Development
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Episodic ataxia type 1 mutations affect fast inactivation of K+ channels by a reduction in either subunit surface expression or affinity for inactivation domain.
Episodic ataxia type 1 (EA1) is an autosomal dominant disorder characterized by continuous myokymia and episodic attacks of ataxia. Mutations in the gene KCNA1 that encodes the voltage-gated potassium channel Kv1.1 are responsible for EA1. In several brain areas, Kv1.1 coassembles with Kv1.4, which confers N-type inactivating properties to heteromeric channels. It is therefore likely that the rate of inactivation will be determined by the number of Kv1.4 inactivation particles, as set by the precise subunit stoichiometry. We propose that EA1 mutations affect the rate of N-type inactivation either by reduced subunit surface expression, giving rise to a reduced number of Kv1.1 subunits in heterotetramer Kv1.1-Kv1.4 channels, or by reduced affinity for the Kv1.4 inactivation domain. To test this hypothesis, quantified amounts of mRNA for Kv1.4 or Kv1.1 containing selected EA1 mutations either in the inner vestibule of Kv1.1 on S6 or in the transmembrane regions were injected into Xenopus laevis oocytes and the relative rates of inactivation and stoichiometry were determined. The S6 mutations, V404I and V408A, which had normal surface expression, reduced the rate of inactivation by a decreased affinity for the inactivation domain while the mutations I177N in S1 and E325D in S5, which had reduced subunit surface expression, increased the rate of N-type inactivation due to a stoichiometric increase in the number of Kv1.4 subunits.
Exercise for the management of type 2 diabetes: a review of the evidence.
Zanuso S1, Jimenez A, Pugliese G, Corigliano G, Balducci S.
The aim is to critically review the more relevant evidence on the interrelationships between exercise and metabolic outcomes. The research questions addressed in the recent specific literature with the most relevant randomized controlled trials, meta-analysis and cohort studies are presented in three domains: aerobic exercise, resistance exercise, combined aerobic and resistance exercise. From this review appear that the effects of aerobic exercise are well established, and interventions with more vigorous aerobic exercise programs resulted in greater reductions in HbA(1c), greater increase in VO(2max) and greater increase in insulin sensitivity. Considering the available evidence, it appears that resistance training could be an effective intervention to help glycemic control, especially considering that the effects of this form of intervention are comparable with what reported with aerobic exercise. Less studies have investigated whether combined resistance and aerobic training offers a synergistic and incremental effect on glycemic control; however, from the available evidences appear that combined exercise training seems to determine additional change in HbA(1c) that can be seen significant if compared with aerobic training alone and resistance training alone.
Voluntary enhanced cocontraction of hamstring muscles during open kinetic chain leg extension exercise: its potential unloading effect on the anterior cruciate ligament.
BACKGROUND: A number of research studies provide evidence that hamstring cocontraction during open kinetic chain knee extension exercises enhances tibiofemoral (TF) stability and reduces the strain on the anterior cruciate ligament.
PURPOSE: To determine the possible increase in hamstring muscle coactivation caused by a voluntary cocontraction effort during open kinetic chain leg-extension exercises, and to assess whether an intentional hamstring cocontraction can completely suppress the anterior TF shear force during these exercises.
STUDY DESIGN: Descriptive laboratory study.
METHODS: Knee kinematics as well as electromyographic activity in the semitendinosus (ST), semimembranosus (SM), biceps femoris (BF), and quadriceps femoris muscles were measured in 20 healthy men during isotonic leg extension exercises with resistance (R) ranging from 10% to 80% of the 1-repetition maximum (1RM). The same exercises were also performed while the participants attempted to enhance hamstring coactivation through a voluntary cocontraction effort. The data served as input parameters for a model to calculate the shear and compressive TF forces in leg extension exercises for any set of coactivation patterns of the different hamstring muscles.
RESULTS: For R≤ 40% 1RM, the peak coactivation levels obtained with intentional cocontraction (l) were significantly higher (P < 10(-3)) than those obtained without intentional cocontraction (l 0). For each hamstring muscle, maximum level l was reached at R = 30% 1RM, corresponding to 9.2%, 10.5%, and 24.5% maximum voluntary isometric contraction (MVIC) for the BF, ST, and SM, respectively, whereas the ratio l/l 0 reached its maximum at R = 20% 1RM and was approximately 2, 3, and 4 for the BF, SM, and ST, respectively. The voluntary enhanced coactivation level l obtained for R≤ 30% 1RM completely suppressed the anterior TF shear force developed by the quadriceps during the exercise.
CONCLUSION: In leg extension exercises with resistance R≤ 40% 1RM, coactivation of the BF, SM, and ST can be significantly enhanced (up to 2, 3, and 4 times, respectively) by a voluntary hamstring cocontraction effort. The enhanced coactivation levels obtained for R≤ 30% 1RM can completely suppress the anterior TF shear force developed by the quadriceps during the exercise.
CLINICAL RELEVANCE: This laboratory study suggests that leg extension exercise with intentional hamstring cocontraction may have the potential to be a safe and effective quadriceps-strengthening intervention in the early stages of rehabilitation programs for anterior cruciate ligament injury or reconstruction recovery. Further studies, including clinical trials, are needed to investigate the relevance of this therapeutic exercise in clinical practice.
Effect of an intensive exercise intervention strategy on modifiable cardiovascular risk factors in subjects with type 2 diabetes mellitus: a randomized controlled trial: the Italian Diabetes and Exercise Study (IDES).
BACKGROUND: This study aimed to assess the efficacy of an intensive exercise intervention strategy in promoting physical activity (PA) and improving hemoglobin A(1c)(HbA(1c)) level and other modifiable cardiovascular risk factors in patients with type 2 diabetes mellitus (T2DM).
METHODS: Of 691 eligible sedentary patients with T2DM and the metabolic syndrome, 606 were enrolled in 22 outpatient diabetes clinics across Italy and randomized by center, age, and diabetes treatment to twice-a-week supervised aerobic and resistance training plus structured exercise counseling (exercise group) vs counseling alone (control group) for 12 months. End points included HbA(1c) level (primary) and other cardiovascular risk factors and coronary heart disease risk scores (secondary).
RESULTS: The mean (SD) volume of PA (metabolic equivalent hours per week) was significantly higher (P < .001) in the exercise (total PA [nonsupervised conditioning PA + supervised PA], 20.0 [0.9], and nonsupervised, 12.4 [7.4]) vs control (10.0 [8.7]) group. Compared with the control group, supervised exercise produced significant improvements (mean difference [95% confidence interval]) in physical fitness; HbA(1c) level (-0.30% [-0.49% to -0.10%]; P < .001); systolic (-4.2 mm Hg [-6.9 to -1.6 mm Hg]; P = .002) and diastolic (-1.7 mm Hg [-3.3 to -1.1 mm Hg]; P = .03) blood pressure; high-density lipoprotein (3.7 mg/dL [2.2 to 5.3 mg/dL]; P < .001) and low-density lipoprotein (-9.6 mg/dL [-15.9 to -3.3 mg/dL]; P = .003) cholesterol level; waist circumference (-3.6 cm [-4.4 to -2.9 cm]; P < .001); body mass index; insulin resistance; inflammation; and risk scores. These parameters improved only marginally in controls.
CONCLUSIONS: This exercise intervention strategy was effective in promoting PA and improving HbA(1c) and cardiovascular risk profile. Conversely, counseling alone, though successful in achieving the currently recommended amount of activity, was of limited efficacy on cardiovascular risk factors, suggesting the need for a larger volume of PA in these high-risk subjects. Trial Registration isrctn.org Identifier: ISRCTN04252749.
Evaluation of the MyWellness Key accelerometer.
OBJECTIVE: to examine the concurrent validity of the Technogym MyWellness Key accelerometer against objective and subjective physical activity (PA) measures.
DESIGN: randomised, cross-sectional design with two phases. The laboratory phase compared the MyWellness Key with the ActiGraph GT1M and the Yamax SW200 Digiwalker pedometer during graded treadmill walking, increasing speed each minute. The free-living phase compared the MyWellness Key with the ActiGraph, Digiwalker, Bouchard Activity cord (BAR) and Global Physical Activity Questionnaire (GPAQ) for seven continuous days. Data were analysed using Spearman rank-order correlation coefficients for all comparisons.
SETTING: laboratory and free-living phases.
PARTICIPANTS: sixteen participants randomly stratified from 41 eligible respondents by sex (n=8 men; n=8 women) and PA levels (n=4 low, n=8 middle and n=4 high active).
RESULTS: there was a strong association between the MyWellness Key and the ActiGraph accelerometer during controlled graded treadmill walking (r=0.91, p<0.01) and in free-living settings (r=0.73-0.76 for light to vigorous PA, respectively, p<0.01). No associations were observed between the MyWellness Key and the BAR and GPAQ (p>0.05).
CONCLUSIONS: the MyWellness Key has a high concurrent validity with the ActiGraph accelerometer to detect PA in both controlled laboratory and free-living settings.
Physical activity/exercise training in type 2 diabetes. The role of the Italian Diabetes and Exercise Study.
Exercise as a public health tool has largely been built around its plausible impact on physical health, including a positive impact on the prevention and management of type 2 diabetes. There is a growing interest in its potential to influence other aspects of quality of life such as mental health and general well-being. The effects of physical activity on overall quality of life are well established in the general population and have been analyzed on various dimensions of the Health-Related Quality of Life (HRQL) including physical and social functioning; subjective well-being, emotion and mood; self esteem and self-perception; cognitive performance; and sleep quality. Even though the effectiveness of physical activity and exercise on physical health has been shown in numerous studies, less evidence is available to show if similar positive improvements in well-being can be seen in subjects with type 2 diabetes. The purpose of this manuscript is to summarize the efficacy of structured exercise counseling on the well-being of type 2 diabetic patients and make some general recommendations. As such, although there is more to be learned about effective strategies in clinical practice, it seems clear that the intervention needs to incorporate individualization and long-term interaction with trained facilitators.
Enjoyment perception during exercise with aerobic machines.
Summary.-This study investigated enjoyment and naturalness of movement perceived during short bouts of exercise with three aerobic machines: treadmill, elliptical crosstrainer, and Vario. The participants were 72 experienced and 60 inexperienced users. Immediately after the exercise with each machine, they filled in a 12-item form of the Physical Activity Enjoyment Scale (PACES) and a Visual Analogue Scales (VAS) about naturalness of movement. Results showed significant within-subjects differences on all scales; exercise with the treadmill and Vario were perceived to be similarly enjoyable and more enjoyable and natural in comparison with the elliptical crosstrainer. Differences in naturalness ratings between experienced and inexperienced users were observed. Exercise was not equally enjoyable when performed with different aerobic machines, and this should be considered by professionals when prescribing aerobic training to enhance motivation and adherence.
Selective contribution of each hamstring muscle to anterior cruciate ligament protection and tibiofemoral joint stability in leg-extension exercise: a simulation study.
A biomechanical model was developed to simulate the selective effect of the co-contraction force provided by each hamstring muscle on the shear and compressive tibiofemoral joint reaction forces, during open kinetic-chain knee-extension exercises. This model accounts for instantaneous values of knee flexion angle [Formula: see text], angular velocity and acceleration, and for changes in magnitude, orientation, and application point of external resistance. The tibiofemoral shear force (TFSF) largely determines the tensile force on anterior cruciate ligament (ACL) and posterior cruciate ligament (PCL). Biceps femoris is the most effective hamstring muscle in decreasing the ACL-loading TFSF developed by quadriceps contractions for [Formula: see text]. In this range, the semimembranosus generates the dominant tibiofemoral compressive force, which enhances joint stability, opposes anterior/posterior tibial translations, and protects cruciate ligaments. The semitendinosus force provides the greatest decreasing gradient of ACL-loading TFSF for [Formula: see text], and the greatest increasing gradient of tibiofemoral compressive force for [Formula: see text]. However, semitendinosus efficacy is strongly limited by its small physiological section. Hamstring muscles behave as a unique muscle in enhancing the PCL-loading TFSF produced by quadriceps contractions for [Formula: see text]. The levels of hamstrings co-activation that suppress the ACL-loading TFSF considerably shift when the knee angular acceleration is changed while maintaining the same level of knee extensor torque by a concurrent adjustment in the magnitude of external resistance. The knowledge of the specific role and the optimal activation level of each hamstring muscle in ACL protection and tibiofemoral stability are fundamental for planning safe and effective rehabilitative knee-extension exercises.
The effect of a strength training program on affect, mood, anxiety, and strength performance in older individuals
Silvano Zanuso, John C. Sieverdes, Nicholas Smith, Attilio Carraro, and Marco Bergamin
The purpose of this study was to evaluate the effect of a strength training program on anxiety, affect, and mood in a group of older adults (≥ 65 years). Twenty men and women participated in a 12-week strength training program. Participants were randomized to an intervention and a waiting list control group. Results showed a significant improvement in the intervention group’s strength scores. Trait anxiety showed a decline in both groups. When mood profiles of participants were analyzed across the initial 12-week of the study, a dimension of mood called Vigor-Activity significantly decreased in the control group while the intervention group’s scores did not change. The affect data showed that negative affect decreased significantly in the intervention group following the training protocol. This study indicates that 12 weeks of strength training results in significant muscle strength increases and moderate improvements of the overall psychological profile.
Development of a Structured Protocol to Determine Multimedia Screen Position on CV Equipment
Bryan Roberts, Ashley Gray, Francesco Bertiato , Paolo Benvenuti , Silvano Zanuso, Ross Weir and Mike Caine
Integrated media screens on cardiovascular (CV) exercise equipment have the potential to increase both adherence and effort of exercising participants. However, watching and interacting with media screens is challenging on CV equipment due to conflicting ergonomic needs of ‘best’ placement for viewing and touching activities. Scientific evaluation is lacking on what is now considered a ‘must have’ feature on modern exercise equipment. The purpose of this study was to develop a protocol for assessing the ergonomics of fixed screens on CV equipment. Fixed screen position preference, based on users’ touching and viewing experience, was compared between 3 methods based on 1 -previous literature including EN ISO 11064-4:2004, 2 - by the user during testing using a free-moving screen, and 3 –the sponsoring company’s settings. The study investigated screen height, angle and distance running on a treadmill and cycling on a stationary upright cycle. Seven recreationally active adults, (mean ± SD; 28 ± 6yrs) were selected based on a representative range of eye heights (1st, 29th, 50th, 82nd and 97th).Each subject completed 6 bouts of 5-min exercise on each respective cardiovascular device comprising the 3 different treadmill or bike screen positions and 2 different user operating conditions. Participants interacted with games on-screen during or simply watched TV whilst wearing headphones. In the bike study, seat-height was based on Lemond’s coefficient (SICI, 2010) and Participants adopted three generic postural positions (normal, city and chrono). The order of conditions was counterbalanced within the subject group. In both the treadmill and bike study, 50th percentile Participants preferred the user defined screen positions, but there was little objection to the manufacturer’s fixed position which was preferred to the anthropometric devised position. The anthropometric devised screen position was deemed ‘unsuitable’ highlighting the lack of understanding in ergonomics for exercise specific requirements. Expert opinion from the manufacturer was within the resulting recommended screen heights, distances and angles recorded from this study. A novel ergonomic assessment method was successfully developed to best understand user preference of fixed touch-screen position when exercising on a treadmill and upright bike with the aim of ‘best’ placing a fixed touch-screen position for 50th percentile eye-height user group. Future studies can employ the principles used in this study and develop this field of ergonomics with the ultimate aim of improving user experience when using exercise equipment.
Changes in insulin sensitivity in response to different modalities of exercise: a review of the evidence.
Type 2 diabetes is an increasingly prevalent condition with complications including blindness and kidney failure. Evidence suggests that type 2 diabetes is associated with a sedentary lifestyle, with physical activity demonstrated to increase glucose uptake and improve glycaemic control. Proposed mechanisms for these effects include the maintenance and improvement of insulin sensitivity via increased glucose transporter type four production. The optimal mode, frequency, intensity and duration of exercise for the improvement of insulin sensitivity are however yet to be identified. We review the evidence from 34 published studies addressing the effects on glycaemic control and insulin sensitivity of aerobic exercise, resistance training and both combined. Effect sizes and confidence intervals are reported for each intervention and meta-analysis presented. The quality of the evidence is tentatively graded, and recommendations for best practice proposed.
Biomechanics of dumbbell/barbell and cable biceps curl exercises
Andrea Biscarini, Rita Borio, Francesco Coscia, Giovanni Mazzolai, Simonetta Simonetti, Gabriella Rosi
A two-dimensional model was developed for dumbbell/barbell and cable biceps curl exercises, in quasi-static and isokinetic regimes. Analytical expressions for the ratios of the biceps force (F) and the tangent (ft) and normal (fn) components of the joint reaction to the dumbbell (Mg) and cable (c) external load were deduced as a function of the joint angle q and the other relevant parameters. For standing/ preacher dumbbell curl, F and fn take their maximum values at the critical wrapping angle q*=27.4°, for any value of the preacher bench inclination a within the range 0²a²90°-q*. An increase of a yields: a) an increase in the initial value of F, and in the peak values of F and |fn| (up to 15Mg and 14Mg, respectively); b) a steeper decrease of F between q* and 180°-a where F=0; c) a shift of the ft(q) curve towards lower joint angles. For a³38°, the joint load becomes of compressive type (fn<0) within the whole range [0,180°-a] of the joint motion. In cable curl, high values of the distance dP of the elbow joint from the pulley center give the same results as the standing dumbbell curl (a=0). When dP approaches the smallest allowed values, the model predicts: a) a steep increase of F and a steep decrease of fn and ft, just above q=0; b) high peak values of F and |fn| at q=q* (up to 15c and 13c, respectively); c) tractional values of fn smaller than 2c and nearly constant values (~3c) of F, above q=100°.
Variation and Heavy External Loads on Hinge Joints
A two-dimensional model has been developed to predict and explain the effects of the variation of muscle moment arms during dynamic exercises involving heavy external loads. The analytical dependence of the muscle moment arm on the joint angle and on the origin and insertion position was derived for an ideal uniaxial hinge joint, modeling the muscle as a cable following an idealized minimum distance path from the origin to insertion that wraps around the bony geometry. Analytical expressions for the ratios of muscular force and the joint restraining reaction components to the external load weight were deduced, for isokinetic and static exercises, as a function of joint angle, joint angular velocity, and the other geometric parameters defining the model. Therefore, external load weight, joint angular velocity, and constraints to joint range of motion may be adjusted reciprocally in order to control in advance the peak value of the components of the joint load during isokinetic exercises. A dynamic formulation of forearm flexion/extension was solved numerically under the condition of constant biceps force in order to highlight the key role played by the variation in muscle moment arm in preventing injury during lifting of external loads against gravity. For example, our analysis indicates that the mean and peak resultant joint loads decrease by 5% and 14%, respectively, as a result of the change in muscle moment arm that occurs over the range of motion.
Biomechanics of Off-Center Monoarticular ExercisesWith Lever Selectorized Equipment
We have developed a 2-D analytical biomechanical model for monoarticular open kinetic-chain exercises with lever selectorized equipment, and different relative placement between the joint center of rotation (J) and the center of rotation (C) of the resistance input lever (“off-center” exercises). All the relevant geometrical aspects of such exercises have been characterized: the change with the joint angle of the distance between the resistance pad (P) and J, and of the angle between CP and JP (i.e., the angle between the resistance input lever and the exercising limb). These changes may strongly affect the joint load and the muscle torque in inverse dynamic problems, given the joint kinematics and the mass of the selected weight stack. Therefore, the muscle torque, the shear and axial components of the joint load have been calculated analytically as a function of the relative positioning of C and J, and the length CP, in addition to the parameters that define the joint kinematics, the equipment mechanics, and the external load. From these results we have derived the optimal cam profiles for “off-center” exercises, as well as the geometrical “off-center” setting that minimizes the shear component of the tibiofemoral joint load in leg extension equipment.
Measurement of Power in Selectorized Strength-Training Equipment
The author derived the exact analytical expression of the instantaneous joint power in exercises with singlejoint, variable-resistance, selectorized strength-training equipment, taking into account all the relevant geometric, kinematic, and dynamic variables of both the movable equipment elements (resistance input lever, cam–pulley system, weight stack) and of the user’s exercising limb. A numerical algorithm was also designed to express, in the presence of a cam, the rectilinear kinematic variables of the weight stack as a function of the rotational kinematic variables of the resistance input lever, and vice versa. Given that information, one can measure the value of the instantaneous and mean joint power exclusively by means of a linear encoder placed on the weight stack or, alternatively, only by the use of an angular encoder placed on the rotational axis of the resistance lever. The results highlight that, for knee extension exercises with leg extension equipment, the real values of both instantaneous and mean joint power may differ by more than 50% in comparison with the values obtained by taking into account only the mass and velocity of the weight stack. These differences are notable not only in explosive exercises, but also whenever considerable joint velocities/accelerations occur within the range of motion.
Joint Torques and Joint Reaction Forces During Squatting With a Forward or Backward Inclined Smith Machine
Andrea Biscarini, Fabio M. Botti, and Vito E. Pettorossi
We developed a biomechanical model to determine the joint torques and loadings during squatting with a backward/forward-inclined Smith machine. The Smith squat allows a large variety of body positioning (trunk tilt, foot placement, combinations of joint angles) and easy control of weight distribution between forefoot and heel. These distinctive aspects of the exercise can be managed concurrently with the equipment inclination selected to unload specific joint structures while activating specific muscle groups. A backward (forward) equipment inclination decreases (increases) knee torque, and compressive tibiofemoral and patellofemoral forces, while enhances (depresses) hip and lumbosacral torques. For small knee flexion angles, the strain-force on the posterior cruciate ligament increases (decreases) with a backward (forward) equipment inclination, whereas for large knee flexion angles, this behavior is reversed. In the 0 to 60 degree range of knee flexion angles, loads on both cruciate ligaments may be simultaneously suppressed by a 30 degree backward equipment inclination and selecting, for each value of the knee angle, specific pairs of ankle and hip angles. The anterior cruciate ligament is safely maintained unloaded by squatting with backward equipment inclination and uniform/forward foot weight distribution. The conditions for the development of anterior cruciate ligament strain forces are clearly explained.
Modeling of the knee joint load in rehabilitative knee extension exercises under water.
A biomechanical and hydrodynamic theoretical model has been developed in order to calculate the knee joint load during underwater knee extension exercises. The hydrodynamic force has been evaluated within the framework of a strip-theory approach, when a blunt rectangular resistive device is applied proximally to the shank to increase its frontal area. Analytical expressions of the patellar tendon force (F(PT)), the axial (phi(n)) and the shear (phi(t)) component of the tibiofemoral joint load have been derived as a function of joint angle (theta), angular velocity (theta ), angular acceleration (theta ), resistive device density, length (L(x)), width (L(z)) and thickness, and average hydrodynamic drag and added mass coefficients. An inverse dynamic problem has been solved, assuming for theta and theta a dependence on theta consistent with the experimental kinematic data available in the literature. The results highlight that the characteristics of the resistive device and the level of muscular activation can be adjusted reciprocally in order to control the peak value of F(PT), phi(n) and phi(t), and the position of these peaks within the joint range of motion (ROM). No anterior cruciate ligament (ACL) stress is observed (phi(t)>0) over the whole ROM, independent of the level of muscular activation, for a light resistive device with L(x) < or = 0.3 m and L(z) < or = 0.4 m. This work highlights that aquatic exercises can be usefully and safely implemented in the rehabilitation program following ACL surgery, and whenever it is important to avoid excessive shear joint forces that constrain the tibial plateau anterior translation with respect to the femur.
Modelling the joint torques and loadings during squatting at the Smith machine.
An analytical biomechanical model was developed to establish the relevant properties of the Smith squat exercise, and the main differences from the free barbell squat. The Smith squat may be largely patterned to modulate the distributions of muscle activities and joint loadings. For a given value of the included knee angle (θ(knee)), bending the trunk forward, moving the feet forward in front of the knees, and displacing the weight distribution towards the forefoot emphasizes hip and lumbosacral torques, while also reducing knee torque and compressive tibiofemoral and patellofemoral forces (and vice versa). The tibiofemoral shear force φ(t) displays more complex trends that strongly depend on θ(knee). Notably, for 180° ≥ θ(knee) ≥ 130°, φ(t) and cruciate ligament strain forces can be suppressed by selecting proper pairs of ankle and hip angles. Loading of the posterior cruciate ligament increases (decreases) in the range 180° ≥ θ(knee) ≥ 150° (θ(knee) ≤ 130°) with knee extension, bending the trunk forward, and moving the feet forward in front of the knees. In the range 150° > θ(knee) > 130°, the behaviour changes depending on the foot weight distribution. The conditions for the development of anterior cruciate ligament strain forces are explained. This work enables careful use of the Smith squat in strengthening and rehabilitation programmes.
Minimization of the knee shear joint load in leg-extension equipment.
We developed an analytical biomechanical model for leg-extension equipment and the associated knee-extension/flexion exercises. The shear component, phi(t), of the tibiofemoral joint load was calculated taking into account all the fundamental elements of the equipment mechanics (resistance pad placement, cam/pulley system geometry, selected weight stack, etc.) and the instantaneous values of the relevant kinematical parameters (knee-flexion angle (theta(f)), angular velocity, and angular acceleration). The optimal distance (a(R))(OPT) between the knee-flexion/extension axis and the resistance pad placement point was derived by minimizing phi(t). (a(R))(OPT) is nearly independent of joint angular velocity and, for appreciably high resistance torques, becomes nearly independent of resistance level and cam/pulley geometry: for theta(f)>40 degrees , phi(t) is minimized by placing the resistance pad distally along the lower leg; for theta(f)<or=40 degrees, phi(t) can be completely eliminated by continuously moving the resistance pad proximally during knee-extension phase and distally during knee-flexion phase (0.17 m<or=(a(R))(OPT)<or=0.4 m). In the presence of knee angular accelerations and hamstrings co-contractions, not predictable in advance, the value of (a(R))(OPT) obtained neglecting these effects still represents a good compromise for joint protection. This work establishes the rational basis for the design and clinical use of a leg-extension equipment that minimizes phi(t).
Determination and optimization of joint torques and joint reaction forces in therapeutic exercises with elastic resistance.
A model has been developed to definitively characterize the resistance properties and the joint loading (i.e., shear and compressive components of the joint reaction force) in single-joint exercises with ideal elastic bands. The model accounts for the relevant geometric and elastic properties of the band, the band pre-stretching, and the relative positioning among the joint center of rotation and the fixation points of the band. All the possible elastic torque profiles of ascending-descending, descending, or ascending type were disclosed in relation to the different ranges of joint angles. From these results the elastic resistance setting that best reproduces the average-user's knee extensor torque in maximal isometric/isokinetic efforts was determined. In this optimized setting, the shear tibiofemoral reaction force corresponding to an anterior (posterior) tibial displacement was 65% smaller than (nearly the same as) that obtained in a cam-equipped leg-extension equipment for equal values of resistance torque peak, whereas the compressive tibiofemoral reaction force was 22% higher. Compared to a weight-stack leg-extension equipment, an elastic resistance optimized setting has the potential to give a more effective quadriceps activation across the range of motion, and greatly reduces the anterior cruciate ligament strain force, which represents the main drawback of existing open kinetic-chain knee-extension exercises.
Validation of the mywellness key in walking and running speeds.
This study was performed to assess the validity of the MyWellness Key (MWK) accelerometer during a treadmill-based protocol. The identification of different exercise intensities is imperative to objectively measure time spent at a specified exercise intensity. Thirty subjects, 15 men and 15 women (age = 24.5 ± 2.6 years; body mass index = 22.5 ± 2.5 kg·m(-1)), participated in a 4-phase treadmill protocol (5 minutes each one) using three different walking velocities (3, 4.5, and 6 km·h(-1)) and run (8 km·h(-1)) while outfitted with a MWK uniaxial accelerometer. Oxygen consumption was measured by indirect calorimetry (ICVO2).
RESULTS: The relationship between VO2 predicted from MWK (MWKVO2) and oxygen consumption (VO2 (ICVO2)), yielded a high and significant correlation (r = 0. 944; p < 0.001) with standard error of estimate (SEE) = 2.42 mL·kg(-1)·min(-1). The average differences between the two methods (MWKVO2 - ICVO2) were -0.79 (-8. 8% at 3 km·h(-1)), -0.02 (-0.2% at 4.5 km·h(-1)), 0.51 (3.3% at 6 km·h(-1)) and -0.74 (-2.7% at 8 km·h(-1)) ml·kg(-1)·min(-1). Only the 3 km·h(-1) speed showed a difference when compared to the criterion measure (p < 0.001). Bland and Altman analysis revealed less than a 1 MET difference in the mean at each point estimate and relatively tight distribution with the standard errors, especially with the 2 moderate walking speeds.
CONCLUSIONS: We found a high correlation between oxygen utilization and the MWK with low standard errors estimates. This indicates that this accelerometer can be used to identify exercise intensities that are related to walking and running. Key pointsFirst laboratory validation of a new uniaxial accelerometer, the MyWellness Key.Results indicate a good exercise intensity prediction during walking at moderate to high speeds.Comparing with other laboratory validations, MyWellness Key exercise intensity detection is aligned with other accelerometers.MyWellness Key can be used to give valid measurements for a range of ambulatory activity in addition to the capabilities to give real-time feedback to the participant in health promotion studies.
Anti-inflammatory effect of exercise training in subjects with type 2 diabetes and the metabolic syndrome is dependent on exercise modalities and independent of weight loss.
BACKGROUND AND AIMS: We investigated the effect of different exercise modalities on high sensitivity-C reactive protein (hs-CRP) and other inflammatory markers in patients with type 2 diabetes and the metabolic syndrome.
METHODS AND RESULTS: Eighty-two patients were randomized into 4 groups: sedentary control (A); receiving counseling to perform low-intensity physical activity (B); performing prescribed and supervised high-intensity aerobic (C) or aerobic+resistance (D) exercise (with the same caloric expenditure) for 12 months. Evaluation of leisure-time physical activity and assessment of physical fitness, cardiovascular risk factors and inflammatory biomarkers was performed at baseline and every 3 months. Volume of physical activity increased and HbA(1c) decreased in Groups B-D. VO(2max), HOMA-IR index, HDL-cholesterol, waist circumference and albuminuria improved in Groups C and D, whereas strength and flexibility improved only in Group D. Levels of hs-CRP decreased in all three exercising groups, but the reduction was significant only in Groups C and D, and particularly in Group D. Changes in VO(2max) and the exercise modalities were strong predictors of hs-CRP reduction, independent of body weight. Leptin, resistin and interleukin-6 decreased, whereas adiponectin increased in Groups C and D. Interleukin-1β, tumor necrosis factor-α and interferon-γ decreased, whereas anti-inflammatory interleukin-4 and 10 increased only in Group D.
CONCLUSION: Physical exercise in type 2 diabetic patients with the metabolic syndrome is associated with a significant reduction of hs-CRP and other inflammatory and insulin resistance biomarkers, independent of weight loss. Long-term high-intensity (preferably mixed) training, in addition to daytime physical activity, is required to obtain a significant anti-inflammatory effect.
Correlates of muscle strength in diabetes: The study on the assessment of determinants of muscle and bone strength abnormalities in diabetes (SAMBA).
Balducci S, Sacchetti M, Orlando G, Salvi L, Pugliese L, Salerno G, D'Errico V, Iacobini C, Conti FG, Zanuso S, Nicolucci A, Pugliese G; Study on the Assessment of Determinants of Muscle and Bone Strength Abnormalities in Diabetes SAMBA Investigators.
BACKGROUND AND AIMS: Apart from late motor nerve dysfunction, factors affecting muscle strength in diabetes are largely unknown. This study was aimed at assessing muscle strength correlates in diabetic subjects encompassing a wide range of peripheral nerve function and various degrees of micro and macrovascular complications.
METHODS AND RESULTS: Four-hundred consecutive patients with type 1 and 2 diabetes (aged 46.4 ± 13.9 and 65.8 ± 10.3 years, respectively) from the Study on the Assessment of Determinants of Muscle and Bone Strength Abnormalities in Diabetes (SAMBA) were examined for upper and lower body muscle isometric maximal voluntary contraction by dynamometry. Univariate and multivariate regression analyses were applied to identify strength correlates. Isometric force at both the upper and lower limbs was significantly lower in subjects with than in those without any complication. At univariate analysis, it was strongly associated with age, diabetes duration, physical activity (PA) level, cardio-respiratory fitness, anthropometric parameters, surrogate measures of complications, and parameters of sensory and autonomic, but not motor (except amplitude) neuropathy. Multivariate analysis revealed that upper and lower body strength correlated independently with male gender and, inversely, with age, autonomic neuropathy score (or individual autonomic function abnormalities), and vibration perception threshold, but not sensory-motor neuropathy score. Diabetes duration and PA level were excluded from the model.
CONCLUSIONS: Both upper and lower body muscle strength correlate with measures of diabetic complications and particularly with parameters of sensory and especially autonomic nerve function, independently of diabetes duration and PA level, thus suggesting the involvement of mechanisms other than manifest motor nerve impairment. Trial Registration number and date: NCT01600924; 05.06.2012.
The Italian Diabetes and Exercise Study (IDES): design and methods for a prospective Italian multicentre trial of intensive lifestyle intervention in people with type 2 diabetes and the metabolic syndrome.
BACKGROUND AND AIMS: The IDES is a prospective Italian multicentre randomized controlled trial to evaluate the efficacy of an intensive lifestyle intervention on modifiable cardiovascular disease (CVD) risk factors in a large cohort of people with type 2 diabetes and the metabolic syndrome.
METHODS AND RESULTS: We recruited 606 subjects with type 2 diabetes and waist circumference >94 cm (M) and >80 cm (F), plus >1 other metabolic syndrome trait (IDF criteria) for both sexes, aged 40-75 years, BMI 27-40 kg/m(2), diabetes duration >1 year with a sedentary lifestyle of >6 months. Patients were randomized into two groups: a control group, receiving conventional care including exercise counselling and an intervention group, treated with a mixed (aerobic and resistance) exercise programme (150 min/week) prescribed and supervised for 12 months. Primary outcome is HbA1c reduction. Secondary outcomes include other traditional and non-traditional risk factors and their relationship to exercise volume/intensity and fitness; dosage of glucose, lipid and blood pressure-lowering drugs; global CVD 10-year risk; patient well-being; and costs.
CONCLUSION: This trial verifies whether a prescribed and supervised exercise programme, including both aerobic and resistance training, is more effective than conventional exercise counselling in reducing modifiable CVD risk factors in type 2 diabetic subjects with the metabolic syndrome.
Reliability and validity of the Mywellness Key physical activity monitor.
BACKGROUND: This study evaluated the reliability and criterion validity of the Mywellness Key accelerometer (MWK) using treadmill protocols and indirect calorimetry.
METHODS: Twenty-five participants completed two four-stage 20-minute treadmill protocols while wearing two MWK accelerometers. Reliability was assessed using raw counts. Validity was assessed by comparing the estimated VO(2) calculated from the MWK with values from respiratory gas exchange.
RESULTS: Good overall and point estimates of reliability were found for the MWK (all intraclass correlations > 0.93). Generalizability theory coefficients showed lower values for running speed (0.70) versus walking speed (all > 0.84), with the majority of the overall percentage of variability derived from the participant (68%-88% of the total 100%). Acceptable validity was found overall (Pearson's r = 0.895-0.902, P < 0.0001), with an overall mean absolute error of 16.22% and a coefficient of variance of 16.92%. Bland-Altman plots showed an overestimation of energy expenditure during the running speed, but total kilocalories were underestimated during the protocol by approximately 10%.
CONCLUSION: Good validity was found during light and moderate walking, while running was slightly overestimated. The MWK may be useful for clinicians and researchers interested in promotion or assessment of physical activity.