A low-power ankle-foot prosthesis for push-off enhancement.

Passive ankle-foot prostheses are light-weighted and reliable, but they cannot generate net positive power, which is essential in restoring the natural gait pattern of amputees. Recent robotic prostheses addressed the problem by actively controlling the storage and release of energy generated during the stance phase through the mechanical deformation of elastic elements housed in the device. This study proposes an innovative low-power active prosthetic module that fits on off-the-shelf passive ankle-foot energy-storage-and-release (ESAR) prostheses. The module is placed parallel to the ESAR foot, actively augmenting the energy stored in the foot and controlling the energy return for an enhanced push-off. The parallel elastic actuation takes advantage of the amputee's natural loading action on the foot's elastic structure, retaining its deformation. The actuation unit is designed to additionally deform the foot and command the return of the total stored energy. The control strategy of the prosthesis adapts to changes in the user's cadence and loading conditions to return the energy at a desired stride phase. An early verification on two transtibial amputees during treadmill walking showed that the proposed mechanism could increase the subjects' dorsiflexion peak of 15.2% and 41.6% for subjects 1 and 2, respectively, and the cadence of about 2%. Moreover, an increase of 26% and 45% was observed in the energy return for subjects 1 and 2, respectively.

An impairment-specific hip exoskeleton assistance for gait training in subjects with acquired brain injury: a feasibility study.

This study was designed to investigate the feasibility and the potential effects on walking performance of a short gait training with a novel impairment-specific hip assistance (iHA) through a bilateral active pelvis orthosis (APO) in patients with acquired brain injury (ABI). Fourteen subjects capable of independent gait and exhibiting mild-to-moderate gait deficits, due to an ABI, were enrolled. Subjects presenting deficit in hip flexion and/or extension were included and divided into two groups based on the presence (group A, n = 6) or absence (group B, n = 8) of knee hyperextension during stance phase of walking. Two iHA-based profiles were developed for the groups. The protocol included two overground gait training sessions using APO, and two evaluation sessions, pre and post training. Primary outcomes were pre vs. post-training walking distance and steady-state speed in the 6-min walking test. Secondary outcomes were self-selected speed, joint kinematics and kinetics, gait symmetry and forward propulsion, assessed through 3D gait analysis. Following the training, study participants significantly increased the walked distance and average steady-state speed in the 6-min walking tests, both when walking with and without the APO. The increased walked distance surpassed the minimal clinically important difference for groups A and B, (respectively, 42 and 57 m > 34 m). In group A, five out of six subjects had decreased knee hyperextension at the post-training session (on average the peak of the knee extension angle was reduced by 36%). Knee flexion during swing phase increased, by 16% and 31%, for A and B groups respectively. Two-day gait training with APO providing iHA was effective and safe in improving walking performance and knee kinematics in ABI survivors. These preliminary findings suggest that this strategy may be viable for subject-specific post-ABI gait rehabilitation.

Serum TSH and Daily Physical Activity in a Cohort of Nonagenarians: Results from the Mugello Study.

BACKGROUND: The current literature does not furnish clear data concerning the relationship between thyroid function, sedentary time and daily physical activity (PA) in older adults with euthyroid condition. The aim of this study was to investigate the association of serum Thyrotropin-Stimulating Hormone (TSH), free Triiodothyronine (fT3) and free Thyroxine (fT4) with sedentary time and PA in a cohort of nonagenarians. METHODS: A total of 108 nonagenarians (92.8 ± 3.2 years), participating in the Mugello Study, and with complete data on thyroid function, sedentary time, PA and sleeping (objectively collected through a multisensory device), were considered for the analysis. RESULTS: Mainly, TSH negatively correlated with time spent lying down, and positively correlated with METs. fT4 levels were negatively associated with mean daily metabolic equivalents (METs) and with low-intensity PA practice (LIPAT), and positively associated with lying down and sleeping time. Similar results have been shown in the female sample. Mainly, participants with high-normal (third tertile) versus low-normal TSH (first tertile) had higher moderate-intensity PA (MIPAT) (p = 0.03). In the female sample, first TSH tertile had higher METs (p = 0.010), LIPAT (p = 0.02), MIPAT (p = 0.01) and lower time lying down (p = 0.04) than third TSH tertile. CONCLUSION: High-normal serum TSH and low-normal fT4 are associated with higher levels and intensity of daily PA, together with higher MIPAT continuity, in the oldest-old.

Lipid and metabolite correlation networks specific to clinical and biochemical covariate show differences associated with sexual dimorphism in a cohort of nonagenarians.

This study defines and estimates the metabolite-lipidic component association networks constructed from an array of 20 metabolites and 114 lipids identified and quantified via NMR spectroscopy in the serum of a cohort of 355 Italian nonagenarians and ultra-nonagenarian. Metabolite-lipid association networks were built for men and women and related to an array of 101 clinical and biochemical parameters, including the presence of diseases, bio-humoral parameters, familiarity diseases, drugs treatments, and risk factors. Different connectivity patterns were observed in lipids, branched chains amino acids, alanine, and ketone bodies, suggesting their association with the sex-related and sex-clinical condition-related intrinsic metabolic changes. Furthermore, our results demonstrate, using a holistic system biology approach, that the characterization of metabolic structures and their dynamic inter-connections is a promising tool to shed light on the dimorphic pathophysiological mechanisms of aging at the molecular level.

Leukocyte-derived ratios are associated with late-life any type dementia: a cross-sectional analysis of the Mugello study.

Immunosenescence, vascular aging, and brain aging, all characterized by elevated levels of inflammatory markers, are thought to share a common pathogenetic pathway: inflamm-aging. Retrospective cross-sectional analysis was conducted using data from the Mugello study (Tuscany, Italy), a representative Italian cohort of free-living nonagenarians. to assess the association between specific peripheral inflammation markers derived from white blood cell counts, and the diagnosis of dementia. All the variables of interest were reported for 411 subjects (110 males and 301 females) out of 475 enrolled in the study. Anamnestic dementia diagnosis was obtained from clinical certificate and confirmed by a General Practitioner, whereas leukocyte ratios were directly calculated from white blood cell counts. Body mass index and comorbidities were considered potential confounders. Diagnosis of any type dementia was certified in 73 cases (17.8%). Subjects affected by dementia were older, more frequently reported a previous stroke, had lower body mass index, and lower Mini-Mental-State-Examination score. Moreover, they had a higher lymphocyte count and lymphocyte-to-monocyte ratio compared to the non-demented nonagenarians. We found that higher levels of lymphocyte counts are cross-sectionally associated with a clinical diagnosis of dementia. Furthermore, lymphocyte-to-monocyte ratio is directly associated with any type of dementia, independently of age, sex, lymphocyte count, and comorbidities. Lymphocyte-to-monocyte ratio may be considered a marker of immunological changes in the brain of dementia patients; moreover, it is low-cost, and easily available, thus enabling comparisons among different studies and populations, although the timeline and the extent of lymphocyte-to-monocyte ratio role in dementia development must be further investigated.

Robot-mediated overground gait training for transfemoral amputees with a powered bilateral hip orthosis: a pilot study.

BACKGROUND: Transfemoral amputation is a serious intervention that alters the locomotion pattern, leading to secondary disorders and reduced quality of life. The outcomes of current gait rehabilitation for TFAs seem to be highly dependent on factors such as the duration and intensity of the treatment and the age or etiology of the patient. Although the use of robotic assistance for prosthetic gait rehabilitation has been limited, robotic technologies have demonstrated positive rehabilitative effects for other mobility disorders and may thus offer a promising solution for the restoration of healthy gait in TFAs. This study therefore explored the feasibility of using a bilateral powered hip orthosis (APO) to train the gait of community-ambulating TFAs and the effects on their walking abilities. METHODS: Seven participants (46-71 years old with different mobility levels) were included in the study and assigned to one of two groups (namely Symmetry and Speed groups) according to their prosthesis type, mobility level, and prior experience with the exoskeleton. Each participant engaged in a maximum of 12 sessions, divided into one Enrollment session, one Tuning session, two Assessment sessions (conducted before and after the training program), and eight Training sessions, each consisting of 20 minutes of robotically assisted overground walking combined with additional tasks. The two groups were assisted by different torque-phase profiles, aiming at improving symmetry for the Symmetry group and at maximizing the net power transferred by the APO for the Speed group. During the Assessment sessions, participants performed two 6-min walking tests (6mWTs), one with (Exo) and one without (NoExo) the exoskeleton, at either maximal (Symmetry group) or self-selected (Speed group) speed. Spatio-temporal gait parameters were recorded by commercial measurement equipment as well as by the APO sensors, and metabolic efficiency was estimated via the Cost of Transport (CoT). Additionally, kinetic and kinematic data were recorded before and after treatment in the NoExo condition. RESULTS: The one-month training protocol was found to be a feasible strategy to train TFAs, as all participants smoothly completed the clinical protocol with no relevant mechanical failures of the APO. The walking performance of participants improved after the training. During the 6mWT in NoExo, participants in the Symmetry and Speed groups respectively walked 17.4% and 11.7% farther and increased walking speed by 13.7% and 17.9%, with improved temporal and spatial symmetry for the former group and decreased energetic expenditure for the latter. Gait analysis showed that ankle power, step width, and hip kinematics were modified towards healthy reference levels in both groups. In the Exo condition metabolic efficiency was reduced by 3% for the Symmetry group and more than 20% for the Speed group. CONCLUSIONS: This study presents the first pilot study to apply a wearable robotic orthosis (APO) to assist TFAs in an overground gait rehabilitation program. The proposed APO-assisted training program was demonstrated as a feasible strategy to train TFAs in a rehabilitation setting. Subjects improved their walking abilities, although further studies are required to evaluate the effectiveness of the APO compared to other gait interventions. Future protocols will include a lighter version of the APO along with optimized assistive strategies.

Thyroid hormone signaling is associated with physical performance, muscle mass, and strength in a cohort of oldest-old: results from the Mugello study.

Thyroid hormones (THs) play a crucial role in the homeostasis of muscle function, such as myogenesis and energy metabolism, suggesting that the thyroid may be also involved in the entropic processes of muscle aging. The aim of the present study is to evaluate the effect of TH signaling on physical performance, muscle mass, and strength in a cohort of community-dwelling oldest-old subjects (> 90 years). The study population was selected in a rural area of central Italy (Mugello, Tuscany), and the design was cross-sectional. Four hundred seventy-five subjects (130 males and 345 females) were enrolled, representing about 65% of all the nonagenarians living in the Mugello area. After adjusting for multiple confounding factors (sex, age, diabetes, and levothyroxine administration), the lowest quartile of FT3/FT4 ratio distribution showed lower physical performance compared to the other quartiles (ß ± SE: - 0.49 ± 0.12; p < 0.001), whereas the highest quartile of FT3/FT4 ratio was associated with higher skeletal muscle index (ß ± SE: 1.11 ± 0.42; p = 0.009). In addition, the lowest quartile of FT4 showed a statistically significant higher handgrip strength (ß ± SE: 1.78 ± 0.68; p = 0.009) compared to all other quartiles. This study demonstrates that nonagenarians with higher FT3/FT4 ratios had better preserved muscle function, therefore successfully overcoming the imbalance of homeostatic and entropic processes involved in muscle aging. However, we could not establish a cause-effect relationship due to the cross-sectional design of the study.

CLOCK gene polymorphisms and quality of aging in a cohort of nonagenarians - The MUGELLO Study.

A total of 356 elderly subjects [257F; 88-106 years] were genotyped for three polymorphisms of the CLOCK gene by TaqMan real-time PCR approach, in order to find associations with quality of aging. Subjects homozygous for the minor allele of rs1801260 were less frequently overweight (p = 0.046), had higher fasting glucose levels (p = 0.037), better scores at the Clock Drawing Test (CDT) (p = 0.047) and worse scores at the Geriatric Depression Scale (p = 0.032). Subjects homozygous for the minor allele of rs11932595 showed higher fasting glucose levels (p = 0.044) and better scores at CDT (p = 0.030). Conversely, subjects homozygous for the minor allele of rs4580704 showed higher triglyceride (p = 0.012), and LDL-cholesterol levels (p = 0.44), and a greater adherence to the Mediterranean diet (MD) (p = 0.044). In addition, AAC, AAG, GGC and AGC (rs1801260-rs11932595-rs4580704) haplotypes were analyzed: AAG was associated with higher risk of overweight (p = 0.008), hypertriglyceridemia (p = 0.040) and hypercholesterolemia (p = 0.036); GGC with lower risk of hyperglycemia (p = 0.022), better sleep pattern (p = 0.001) and with better score at mini-mental state examination (p = 0.010); AGC with lower risk of depression (p = 0.026) and AAC with lower adherence to the MD (p = 0.028). Therefore, CLOCK gene polymorphisms let us hypothesize an involvement in the quality of aging in a cohort of nonagenarians.

The Challenges and Achievements of Experimental Implementation of an Active Transfemoral Prosthesis Based on Biological Quasi-Stiffness: The CYBERLEGs Beta-Prosthesis.

The CYBERLEGs Beta-Prosthesis is an active transfemoral prosthesis that can provide the full torque required for reproducing average level ground walking at both the knee and ankle in the sagittal plane. The prosthesis attempts to produce a natural level ground walking gait that approximates the joint torques and kinematics of a non-amputee while maintaining passively compliant joints, the stiffnesses of which were derived from biological quasi-stiffness measurements. The ankle of the prosthesis consists of a series elastic actuator with a parallel spring and the knee is composed of three different systems that must compliment each other to generate the correct joint behavior: a series elastic actuator, a lockable parallel spring and an energy transfer mechanism. Bench testing of this new prosthesis was completed and demonstrated that the device was able to create the expected torque-angle characteristics for a normal walker under ideal conditions. The experimental trials with four amputees walking on a treadmill to validate the behavior of the prosthesis proved that although the prosthesis could be controlled in a way that allowed all subjects to walk, the accurate timing and kinematic requirements of the output of the device limited the efficacy of using springs with quasi-static stiffnesses. Modification of the control and stiffness of the series springs could provide better performance in future work.

Gastrocnemius Myoelectric Control of a Robotic Hip Exoskeleton Can Reduce the User's Lower-Limb Muscle Activities at Push Off.

We present a novel assistive control strategy for a robotic hip exoskeleton for assisting hip flexion/extension, based on a proportional Electromyography (EMG) strategy. The novelty of the proposed controller relies on the use of the Gastrocnemius Medialis (GM) EMG signal instead of a hip flexor muscle, to control the hip flexion torque. This strategy has two main advantages: first, avoiding the placement of the EMG electrodes at the human-robot interface can reduce discomfort issues for the user and motion artifacts of the recorded signals; second, using a powerful signal for control, such as the GM, could improve the reliability of the control system. The control strategy has been tested on eight healthy subjects, walking with the robotic hip exoskeleton on the treadmill. We evaluated the controller performance and the effect of the assistance on muscle activities. The tuning of the assistance timing in the controller was subject dependent and varied across subjects. Two muscles could benefit more from the assistive strategy, namely the Rectus Femoris (directly assisted) and the Tibialis Anterior (indirectly assisted). A significant correlation was found between the timing of the delivered assistance (i.e., synchronism with the biological hip torque), and reduction of the hip flexors muscular activity during walking; instead, no significant correlations were found for peak torque and peak power. Results suggest that the timing of the assistance is the most significant parameter influencing the effectiveness of the control strategy. The findings of this work could be important for future studies aimed at developing assistive strategies for walking assistance exoskeletons.

Ligation of the saphenofemoral junction tributaries as risk factor for groin recurrence.

OBJECTIVE: The aim of this study was to compare the recurrence rate after high ties performed with or without sparing of the saphenofemoral junction tributaries. METHODS: There were 867 lower limbs enrolled. All patients underwent a high tie with (group A) or without (group B) ligation of all the junctional tributaries for a great saphenous vein reflux (C2-5EpAsPr). A duplex ultrasound examination detected recurrences. RESULTS: Median follow-up was 5 years (interquartile range, 3-8 years). Group A had a higher recurrence rate than group B (odds ratio, 7.52; P < .001). Group A recurrences (7.4%), compared with group B (1.1%), presented with a more frequent direct stump reconnection (3.7% vs 0.2%; P < .001) or newly developed pelvic shunts (3% vs 0.5%; P < .001). No significant difference was reported between the two groups in newly incompetent perforating veins. CONCLUSIONS: Ligation of the junctional tributaries is associated with a higher recurrence risk. Further investigations are needed to determine the hemodynamic role of each single junctional tributary.

Hemoglobin concentration is associated with self-reported disability and reduced physical performance in a community dwelling population of nonagenarians: the Mugello Study.

People aged 90 and older represent a fast-growing population segment who deserve specific attention and research. Aging is associated with a progressive decrease in hemoglobin concentration, which predicts adverse outcome, such as mortality, morbidity, frailty and disability. Whether this association is independent from increased prevalence of comorbidity, causing both anemia and reduced physical function is yet under debate. The aim of this study is to explore the relationship between hemoglobin concentration and self-reported disability and reduced physical performance in a community dwelling population of nonagenarians. Data presented were collected in the framework of the Mugello Study, a clinical epidemiologic survey of nonagenarians living in the Mugello area (Tuscany, Italy). 251 persons (177 women, age 93.2 ± 3.3 years; 74 men, age 92.2 ± 2.5 years) underwent a blood draw. Along with hemoglobin concentration, self-reported disability (basic and instrumental activities of daily living), physical performance (Short Physical Performance Battery), self-reported physical activity and muscular strength (handgrip measurement) were assessed. Covariates, inherent sociodemographic and health indicators and comorbidities were also included in the analysis. This study confirms that anemia is very common in the oldest old, with a significantly higher prevalence in males (50% in men vs 24% in women). Multiple linear regression analysis, including all the comorbid conditions as confounding factors, shows that hemoglobin concentration is independently associated with handgrip strength, self-reported physical activity and disability in dressing, and taking a shower/bath. In conclusion, results from this study confirm that in the oldest old, low hemoglobin concentration is strongly associated with self-reported disability and decline of physical performance independent of comorbidity.

Whole Body Awareness for Controlling a Robotic Transfemoral Prosthesis.

Restoring locomotion functionality of transfemoral amputees is essential for early rehabilitation treatment and for preserving mobility and independence in daily life. Research in wearable robotics fostered the development of innovative active mechatronic lower-limb prostheses designed with the goal to reduce the cognitive and physical effort of lower-limb amputees in rehabilitation and daily life activities. To ensure benefits to the users, active mechatronic prostheses are expected to be aware of the user intention and properly interact in a closed human-in-the-loop paradigm. In the state of the art various cognitive interfaces have been proposed to online decode the user's intention. Electromyography in combination with mechanical sensing such as inertial or pressure sensors is a widely adopted solution for driving active mechatronic prostheses. In this framework, researchers also explored targeted muscles re-innervation for an objective-oriented surgical amputation promoting wider usability of active prostheses. However, information kept by the neural component of the cognitive interface deteriorates in a prolonged use scenario due to electrodes-related issues, thereby undermining the correct functionality of the active prosthesis. The objective of this work is to present a novel controller for an active transfemoral prosthesis based on whole body awareness relying on a wireless distributed non-invasive sensory apparatus acting as cognitive interface. A finite-state machine controller based on signals monitored from the wearable interface performs subject-independent intention detection of functional tasks such as ground level walking, stair ascent, and sit-to-stand maneuvres and their main sub-phases. Experimental activities carried out with four transfemoral amputees (among them one dysvascular) demonstrated high reliability of the controller capable of providing 100% accuracy rate in treadmill walking even for weak subjects and low walking speeds. The minimum success rate was of 94.8% in performing sit-to-stand tasks. All the participants showed high confidence in using the transfemoral active prosthesis even without training period thanks to intuitiveness of the whole body awareness controller.

Physical human-robot interaction of an active pelvis orthosis: toward ergonomic assessment of wearable robots.

BACKGROUND: In human-centered robotics, exoskeletons are becoming relevant for addressing needs in the healthcare and industrial domains. Owing to their close interaction with the user, the safety and ergonomics of these systems are critical design features that require systematic evaluation methodologies. Proper transfer of mechanical power requires optimal tuning of the kinematic coupling between the robotic and anatomical joint rotation axes. We present the methods and results of an experimental evaluation of the physical interaction with an active pelvis orthosis (APO). This device was designed to effectively assist in hip flexion-extension during locomotion with a minimum impact on the physiological human kinematics, owing to a set of passive degrees of freedom for self-alignment of the human and robotic hip flexion-extension axes. METHODS: Five healthy volunteers walked on a treadmill at different speeds without and with the APO under different levels of assistance. The user-APO physical interaction was evaluated in terms of: (i) the deviation of human lower-limb joint kinematics when wearing the APO with respect to the physiological behavior (i.e., without the APO); (ii) relative displacements between the APO orthotic shells and the corresponding body segments; and (iii) the discrepancy between the kinematics of the APO and the wearer's hip joints. RESULTS: The results show: (i) negligible interference of the APO in human kinematics under all the experimented conditions; (ii) small (i.e., < 1 cm) relative displacements between the APO cuffs and the corresponding body segments (called stability); and (iii) significant increment in the human-robot kinematics discrepancy at the hip flexion-extension joint associated with speed and assistance level increase. CONCLUSIONS: APO mechanics and actuation have negligible interference in human locomotion. Human kinematics was not affected by the APO under all tested conditions. In addition, under all tested conditions, there was no relevant relative displacement between the orthotic cuffs and the corresponding anatomical segments. Hence, the physical human-robot coupling is reliable. These facts prove that the adopted mechanical design of passive degrees of freedom allows an effective human-robot kinematic coupling. We believe that this analysis may be useful for the definition of evaluation metrics for the ergonomics assessment of wearable robots.

Experimental Validation of Motor Primitive-Based Control for Leg Exoskeletons during Continuous Multi-Locomotion Tasks.

An emerging approach to design locomotion assistive devices deals with reproducing desirable biological principles of human locomotion. In this paper, we present a bio-inspired controller for locomotion assistive devices based on the concept of motor primitives. The weighted combination of artificial primitives results in a set of virtual muscle stimulations. These stimulations then activate a virtual musculoskeletal model producing reference assistive torque profiles for different locomotion tasks (i.e., walking, ascending stairs, and descending stairs). The paper reports the validation of the controller through a set of experiments conducted with healthy participants. The proposed controller was tested for the first time with a unilateral leg exoskeleton assisting hip, knee, and ankle joints by delivering a fraction of the computed reference torques. Importantly, subjects performed a track involving ground-level walking, ascending stairs, and descending stairs and several transitions between these tasks. These experiments highlighted the capability of the controller to provide relevant assistive torques and to effectively handle transitions between the tasks. Subjects displayed a natural interaction with the device. Moreover, they significantly decreased the time needed to complete the track when the assistance was provided, as compared to wearing the device with no assistance.

Risk of malnutrition in a sample of nonagenarians: Specific versus classic bioelectrical impedance vector analysis.

OBJECTIVES: The aims were to describe the body composition and the risk of malnutrition in a sample of nonagenarians and to identify what bioelectrical impedance vector analysis (BIVA) approach (classic or specific) is more correlated with either the risk of malnutrition or various anthropometric parameters. METHODS: In the Mugello area (Italy), a representative sample of nonagenarians was enrolled in a survey aimed at investigating various health issues, including those related to nutritional status. The nutritional status was investigated using body mass index (BMI), mid-upper arm circumference (MUAC), calf circumference (CC), Malnutrition Universal Screening Tool (MUST), and BIVA. Two different approaches were used for the BIVA data analysis: the classic method and the specific method. RESULTS: All measurements were obtained from 321 nonagenarians (65.7% of the enrolled sample; 92 men and 229 women); 74.8% of the subjects were at low risk of malnutrition according to MUST, 62.5% exhibited CC values higher than 31 cm, and 86.8% exhibited MUAC values higher than 22 cm. The bioelectrical parameters varied with nutritional status, independent of the nutritional indicator used; the parameters also varied based on sex and BIVA approach. The bioelectrical parameters obtained by the specific BIVA approach were more strongly correlated with MUST score, MUAC, and CC values compared with the parameters calculated using the classic approach. CONCLUSIONS: Our study produced findings relevant to particular aspects of population aging. Above all, the specific BIVA was more effective at assessing nutritional status based on both anthropometric parameters and the risk of malnutrition.

Ability to work in anaerobic condition is associated with physical performance on the six-minute walk test in older patients receiving cardiac rehabilitation.

OBJECTIVE: During maximal incremental exercise, the ability to work in the anaerobic condition, expressed by the respiratory exchange ratio, is associated with physical performance. Further, peak respiratory exchange ratio is regarded as the best non-invasive measure of a patient's actual exercise effort. This study examined whether ability to work in the anaerobic condition is also associated with physical performance in submaximal constant work rate exercise. SUBJECTS AND METHODS: A total of 75 older patients (51 men, 24 women), mean age 71.1 years (standard deviation 6.7 years), who had recently undergone cardiac surgery, performed cardiopulmonary exercise testing in a 6-min walk test before and after rehabilitation. RESULTS: The distance walked, steady-state oxygen uptake, carbon dioxide output and respiratory exchange ratio increased significantly after rehabilitation (p < 0.001 for all). In multivariable models predicting the distance walked before and after rehabilitation, higher steady-state respiratory exchange ratio was independently associated with longer distance (p < 0.001 for both). CONCLUSION: In older patients receiving post-acute cardiac rehabilitation the ability to work in the anaerobic condition is associated with physical performance in submaximal constant work rate exercises. Thus the steady-state respiratory exchange ratio might be regarded as a measure of the patient's actual exercise effort. This information may prove useful in customizing exercise prescription and assessing the effects of rehabilitation.

Effects of lower limb length and body proportions on the energy cost of overground walking in older persons.

BACKGROUND: Although walking has been extensively investigated in its biomechanical and physiological aspects, little is known on whether lower limb length and body proportions affect the energy cost of overground walking in older persons. METHODS: We enrolled 50 men and 12 women aged 65 years and over, mean 69.1 ± SD 5.4, who at the end of their cardiac rehabilitation program performed the six-minute walk test while wearing a portable device for direct calorimetry and who walked a distance comparable to that of nondisabled community-dwelling older persons. RESULTS: In the multivariable regression model (F = 12.75, P < 0.001, adjusted R(2) = 0.278) the energy cost of overground walking, expressed as the net energy expenditure, in kg(-1) sec(-1), needed to provide own body mass with 1 joule kinetic energy, was inversely related to lower limb length and directly related to lower limb length to height ratio (ß ± SE(ß) = -3.72 × 10(-3) ± 0.74 × 10(-3), P < 0.001, and 6.61 × 10(-3) ± 2.14 × 10(-3), P = 0.003, resp.). Ancillary analyses also showed that, altogether, 1 cm increase in lower limb length reduced the energy cost of overground walking by 2.57% (95%CI 2.35-2.79). CONCLUSIONS: Lower limb length and body proportions actually affect the energy cost of overground walking in older persons.

Ventilatory strategies in the six-minute walk test in older patients receiving a three-week rehabilitation programme after cardiac surgery through median sternotomy.

BACKGROUND: Although the six-minute walk test (6MWT) is widely used in cardiac rehabilitation, little is known about the ventilatory strategies adopted by older patients who have recently undergone median sternotomy, in order to meet the increased metabolic demand in the 6MWT. METHODS: Using a portable gas-analyser we assessed the breathing patterns in the 6MWT before and after a 3-week rehabilitation programme in 84 older patients, 58 men and 26 women, mean age 71 years (standard deviation (SD) 6 years), who had undergone median sternotomy. RESULTS: After rehabilitation, patients increased end-test ventilation (33.1 l (SD 9.8) vs. 30.9 l (SD 8.4), p < 0.001) by increasing tidal volume (1.158 l (SD 0.298) vs. 1.065 l (SD 0.255), p < 0.001), while breathing frequency remained unchanged (29.9 bpm (SD 5.4) vs. 30.2 bpm (SD 5.8), p = 0.621). As a consequence, the ventilatory equivalent for CO2, was significantly improved (39.9 (SD 5.3) vs. 43.5 (SD 7.4), p < 0.001). Furthermore, the improvement in ventilatory efficiency was significantly (p < 0.001) correlated with the improvement in the distance walked on the 6MWT. CONCLUSION: Older patients who have undergone median sternotomy meet the increased metabolic demand on the 6MWT after cardiac rehabilitation by increasing tidal volume. Accordingly, we should consider including as a routine specific exercises for inspiratory muscle training in current rehabilitation programmes to reduce inspiratory muscle effort and further improve ventilatory efficiency.

Effects of a structured physical activity intervention on measures of physical performance in frail elderly patients after cardiac rehabilitation: a pilot study with 1-year follow-up.

The objective of this prospective randomized controlled study was to compare the long-term effects of a structured physical activity intervention with those of aerobic exercises alone, in a cohort of elderly patients who had undergone elective cardiac surgery, and who were classified as frail at the end of rehabilitation based on their Short Physical Performance Battery (SPPB) score. At the end of rehabilitation, 140 frail elderly patients were randomly allocated either to the intervention group (IG) or to the control group (CG). CG participants received the usual aerobic exercise prescription, while IG participants were also taught additional exercises for strength, flexibility, balance and coordination. The improvement in SPPB score after 1 year was the outcome of the study. IG showed a significant improvement in SPPB score (9.0 ± 1.1 vs. 7.7 ± 1.4, p < 0.001), while no significant change was found in CG (7.7 ± 1.6 vs. 7.6 ± 1.5, p = 0.252). IG also showed a significantly higher proportion of participants who improved their SPPB score of at least 1 point (70 vs. 37%, p < 0.001). In conclusions, our structured physical activity intervention significantly improves the SPPB score in frail elderly patients who have undergone elective cardiac surgery. An intervention that improves the SPPB score might delay the occurrence of mobility disability.