Type of exercise may influence postural adaptations in chemotherapy-induced peripheral neuropathy

OBJECTIVE

Traditional posturography measurements characterize postural instability in patients with chemotherapy-induced peripheral neuropathy (CIPN), while underlying postural control mechanisms remain unclear. Taking a model-based approach can yield insights into these mechanisms. This study's aim was to characterize the modifications in postural control of CIPN patients associated with exercise in relation to the postural behavior of healthy control participants (hCON) via an exploratory approach.

METHODS

Thirty-one CIPN patients were randomly assigned to two interventions (balance plus moderate endurance training vs. moderate endurance training only) and exercised twice per week over 12 weeks. Baseline data were compared to 36 matched hCONs. We recorded spontaneous sway and postural reactions to platform tilts using Optotrak and a Kistler force platform pre- and post-intervention. Data interpretation relied on a model-based parameter identification procedure.

RESULTS

Spontaneous sway amplitudes were larger and postural reactions smaller, with a relative phase advance, in our pre-intervention patients than the hCONs. Post-intervention, spontaneous sway, and postural reactions were reduced and the sensory-motor ratio larger in both groups, while the postural reaction timing differed between groups.

INTERPRETATION

The abnormally small postural reactions in CIPN patients before the intervention can be interpreted as the consequence of abnormally strong velocity control-a strategy modification that may serve as a prediction mechanism to compensate for the lack of timely and accurate proprioceptive signals. While both groups reduced postural sway and showed an adapted sensory-motor ratio post-intervention, the interventions seemed to trigger different velocity control strategies. This study emphasizes the need for taking a more differentiated perspective on intervention effects.

TRIAL REGISTRATION

German Clinical Trials Register (DRKS) number: DRKS00005419, prospectively registered on November 19, 2013.

Power Output and Efficiency During Supine, Recumbent, and Upright Cycle Ergometry

Recumbent and supine cycling are common exercise modes in rehabilitation and clinical settings but the influence of postures on work efficiency is unclear. Therefore, the aim of this study was to compare metabolic and ventilatory efficiency during upright, recumbent, and supine postures. Potential differences should be assessed for suitable diagnostics and for prescriptions of training that probably is performed in alternative postures. Eighteen healthy subjects (age: 47.2 ± 18.4 years; 10 female, 8 male) participated in the study and each completed three incremental cycle ergometer tests until exhaustion in upright, recumbent (40°), and supine positions. Gas exchange, heart rate (HR), and lactate concentrations were analyzed and efficiency was calculated subsequently. Testing sessions were performed in random order within a 2-week period. Upright cycling resulted in significantly higher peak values [power output, oxygen uptake (Vo₂), HR] as well as performance at lactate and ventilatory thresholds in comparison to recumbent or supine positions. Vco₂/Vo₂ slope and ventilatory efficiency (VE/Vco₂ slope) were not affected by posture. Aerobic work efficiency (Vo₂/P slope) and gross efficiency (GE) differed significantly between postures. Hereby, GE was lowest in supine cycling, particularly obvious in a mainly aerobic condition at 70 Watt [Median 11.6 (IQR 10.9-13.3) vs. recumbent: 15.9 (IQR 15.6-18.3) and upright: 17.4 (IQR 15.1-18.3)]. Peak power as well as GE and work efficiency values are influenced by cycling position, reinforcing the importance of adjusting test results for training prescriptions. Surprisingly, ventilatory efficiency was not affected in this study and therefore does not seem to falsify test results for pulmonary diagnostics.

Cardiopulmonary performance in allogeneic hematopoietic cell transplantation recipients-evaluation of pre-transplant risk assessments

Cardiopulmonary performance reflects how well different organ systems interact. It is inter alia influenced by body composition, determines patients' quality of life and can also predict mortality. However, it is not yet used for risk prediction prior to allogeneic hematopoietic cell transplantations (alloHCT). Thus, we aimed to examine the predictive power of peak oxygen consumption (VO2peak) as a representative of cardiopulmonary performance and that of body composition before alloHCT to determine overall survival (OS) and non-relapse mortality (NRM) 2 years after transplantation. We also compared it with the predictive power of four commonly-used risk scores: revised Pretransplant Assessment of Mortality (rPAM), Hematopoietic Cell Transplantation-specific Comorbidity Index (HCT-CI), revised Disease Risk Index (rDRI), European Society for Blood and Marrow Transplantation (EBMT). Fifty-nine patients performed a cardiopulmonary exercise test and body composition assessments before alloHCT and were observed for 2 years. Sixteen patients died. VO2peak and most risk scores assessed pre-transplant revealed no association with OS or NRM. Body composition parameters only within univariable analyses. But higher rDRI and the male sex, were associated with shorter OS and higher NRM. We thus propose that the current risk assessments be reconsidered. The predictive value of VO2peak and body composition need further clarification, however.

Gait Analysis of Patients After Allogeneic Hematopoietic Cell Transplantation Reveals Impairments of Functional Performance

Background: After allogeneic hematopoietic cell transplantation (alloHCT), patients often report functional impairments like reduced gait speed and muscle weakness. These impairments can increase the risk of adverse health events similar to elderly populations. However, they have not been quantified in patients after alloHCT (PATs). Methods: We compared fear of falling (Falls Efficacy Scale–International) and temporal gait parameters recorded on a 10-m walkway at preferred and maximum gait speed and under dual-task walking of 16 PATs (aged 31-73 years) with 15 age-matched control participants (CONs) and 17 seniors (SENs, aged >73 years). Results: Groups’ gait parameters especially differed during the maximum speed condition: PATs walked slower and required more steps/10 m than CONs. PATs exhibited greater stride, stance, and swing times than CONs. PATs’ swing time was even longer than SENs’. The PATs’ ability to accelerate their gait speed from preferred to fast was smaller compared with CONs’. PATs reported a greater fear of falling than CONs and SENs. Conclusion: Gait analysis of alloHCT patients has revealed impairments of functional performance. Patients presented a diminished ability to accelerate gait and extending steps possibly related to a notable strength deficit that impairs power-generation abilities from lower extremities. Furthermore, patients reported a greater fear of falling than control participants and even seniors. Slowing locomotion could be a risk-preventive safety strategy. Since functional disadvantages may put alloHCT patients at a higher risk of frailty, reinforcing appropriate physical exercises already during and after alloHCT could prevent adverse health events and reduce the risk of premature functional aging.

Whole body vibration training during allogeneic hematopoietic cell transplantation-the effects on patients' physical capacity

Patients undergoing allogeneic hematopoietic cell transplantation (alloHCT) experience a considerable decline in physical and psycho-social capacity. Since whole body vibration (WBV) is known to efficiently stimulate the neuromuscular system and enhance cardiorespiratory fitness and muscle strength in frail individuals, we hypothesized that WBV would maintain various physical and psychological capacities in patients during alloHCT. Seventy-one patients were randomly allocated to either an intervention group (IG) doing WBV or an active control group (CG) doing mobilization exercises five times per week. We determined peak oxygen consumption (VO_2peak) and maximum power, maximum strength, functional performance, body composition, quality of life (QoL), and fatigue. Tests were carried out before conditioning therapy, at hospital discharge and at day ± 180 (follow-up). As 18 patients did not participate in post-intervention assessment and follow-up data from 9 patients was not collectible, per-protocol (PP) analysis of 44 patients is presented. During hospitalization, WBV maintained maximum strength, height, and power output during jumping, as well as reported QoL, physical functioning, and fatigue level compared with mobilization. At follow-up, relative VO_2peak (p = 0.035) and maximum power (p = 0.011), time and power performing chair-rising test (p = 0.022; p = 0.009), and reported physical functioning (p = 0.035) significantly increased in the IG, while fatigue decreased (p = 0.005). CG’s body cell mass and phase angle had significantly decreased at follow-up (p = 0.002; p = 0.004). Thus, WBV might maintain maximum strength, functional performance, QoL, and fatigue during alloHCT, while cardiorespiratory fitness might benefit from accelerated recovery afterwards.

A new approach to characterize postural deficits in chemotherapy-induced peripheral neuropathy and to analyze postural adaptions after an exercise intervention

Background

Postural instability presents a common and disabling consequence of chemotherapy-induced peripheral neuropathy (CIPN). However, knowledge about postural behavior of CIPN patients is sparse. With this pilot study, we used a new approach to i) characterize postural impairments as compared to healthy subjects, ii) allocate possible abnormalities to a set of parameters describing sensorimotor function, and iii) evaluate the effects of a balance-based exercise intervention.

Methods

We analyzed spontaneous and externally perturbed postural control in eight CIPN patients before and after a balance-based exercise intervention by using a modification of an established postural control model. These findings were compared to 15 matched healthy subjects.

Results

Spontaneous sway amplitude and velocity were larger in CIPN patients compared to healthy subjects. CIPN patients’ reactions to external perturbations were smaller compared to healthy subjects, indicating that patients favor vestibular over proprioceptive sensory information. The balance-based exercise intervention up-weighted proprioceptive information in patients.

Conclusions

CIPN patients’ major postural deficit may relate to underuse of proprioceptive information that results in a less accurate posture control as spontaneous sway results indicate. The balance-based exercise intervention is able to partially correct for this abnormality. Our study contributes to a better understanding of postural impairments in CIPN patients and suggests an effective treatment strategy.

Trial registration

German Clinical Trials Register: DRKS00004340, retrospectively registered 04 January 2013.

It's never too late - balance and endurance training improves functional performance, quality of life, and alleviates neuropathic symptoms in cancer survivors suffering from chemotherapy-induced peripheral neuropathy: results of a randomized controlled trial

Background

Chemotherapy-induced peripheral neuropathy (CIPN) can affect functional performance and quality of life considerably. Since balance training has proven to enhance physical function, it might be a promising strategy to manage CIPN-induced functional impairments.

Methods

Fifty cancer survivors with persisting CIPN after finishing their treatment were randomly allocated to an intervention (IG) or active control group (CG). The IG did endurance plus balance training, the CG only endurance training (twice weekly over 12 weeks). Pre- and post-assessments included functional performance, cardiorespiratory fitness, vibration sense, and self-reported CIPN symptoms (EORTC QLQ-CIPN20).

Results

Intention-to-treat analyses (n = 41) did not reveal a significant group difference (CG minus IG) for sway path in semi-tandem stance after intervention (primary endpoint), adjusted for baseline. However, our per-protocol analysis of 37 patients with training compliance ≥70% revealed: the IG reduced their sway path during semi-tandem stance (− 76 mm, 95% CI -141 – -17; CG: -6 mm, 95% CI -52 – 50), improved the duration standing on one leg on instable surface (11 s, 95% CI 8–17; CG: 0 s, 95%CI 0–5) and reported decreased motor symptoms (−8points, 95% CI -18 – 0; CG: -2points 95% CI -6 – 2). Both groups reported reduced overall- (IG: -10points, 95% CI -17 – -4; CG: -6points, 95% CI -11 – -1) and sensory symptoms (IG: -7points, 95% CI -15 – 0; CG: -7points, 95% CI -15 – 0), while only the CG exhibited objectively better vibration sense (knuckle: 0.8points, 95% CI 0.3–1.3; IG: 0.0points, 95% CI -1.1 – 0.9; patella: 1.0points, 95% CI 0.4–1.6: IG: -0.8points, 95% CI -0.2 – 0.0). Furthermore, maximum power output during cardiopulmonary exercise test increased in both groups (IG and CG: 0.1 W/kg, 95% CI 0.0–0.2), but only the CG improved their jump height (2 cm, 95% CI 0.5–3.5; IG: 1 cm, 95% CI -0.4 – 3.2).

Conclusion

We suppose that endurance training induced a reduction in sensory symptoms in both groups, while balance training additionally improved patients’ functional status. This additional functional effect might reflect the IG’s superiority in the CIPN20 motor score. Both exercises provide a clear and relevant benefit for patients with CIPN.

Trial registration

German Clinical Trials Register (DRKS) number: DRKS00005419, prospectively registered on November 19, 2013.

Feasibility of whole body vibration during intensive chemotherapy in patients with hematological malignancies - a randomized controlled pilot study

BACKGROUND

Hospitalized cancer patients undergoing intensive or high-dose chemotherapy often experience a considerable decline in functional performance associated with the increased risk of adverse health events. Exercises, particularly resistance-based exercises that may counteract this decline are restricted by therapy-related side effects. Since whole body vibration (WBV) is known to efficiently stimulate the neuromuscular system without significantly raising blood pressure, we hypothesize that especially WBV is particularly feasible even during intensive or high-dose chemotherapy (primary endpoint) and thus induces beneficial functional adaptations.

METHODS

Twenty hospitalized patients with hematological malignancies scheduled for intensive or high-dose chemotherapy were randomly allocated to an intervention group (IG) undergoing WBV, or an active control group (CG) cycling. Feasibility was determined by comparing the IG's and CG's training compliance. Furthermore, to assess feasibility, WBV-induced changes in chemotherapy-related side effects, blood pressure, and heart rate immediately after exercising were documented. To assess patients' functional performance, we measured jump height (cm), the duration (sec) of performing the chair rising- (CRT) and timed-up-and-go test (TUG), maximum power output during jumping and CRT (watt/kg) as well as sway path (mm) during balance tasks.

RESULTS

Training compliance was similar between groups (IG: median 62%, range 39-77; CG: 67%, 58-100; p = 0.315). Moreover, we observed neither the IG's reported side effects worsening, nor any increase in blood pressure after WBV. IG's jump height (+ 2.3 cm, 95%CI 0.1-4.4, p = 0.028) and TUG performance (- 1.3 s, 95%CI -2.53 - -0.65, p = 0.027) improved significantly, while sway paths in semi-tandem stance were augmented after the intervention (eyes open: + 60 mm, 95%CI 2-236, p = 0.046; eyes closed: + 88 mm, 95%CI 49-214, p = 0.028). The CG's performances did not change over time. Maximum power output during CMJ and CRT and time during CRT did not change.

CONCLUSION

Our study is the first proving the feasibility of WBV during intensive/high-dose chemotherapy of hospitalized cancer patients. Additionally, WBV-induced neuromuscular adaptations resulted in functional benefits relevant to patients' autonomy. We believe that WBV can be implemented as an alternative training method during intensive chemotherapy, although the relative benefit compared to conventional resistance training requires more evaluation in future studies.

TRIAL REGISTRATION

German Register of Clinical Trials No.: DRKS00004338 , prospectively registered on 11/30/2012.

Results From a Pilot Study of Handheld Vibration: Exercise Intervention Reduces Upper-Limb Dysfunction and Fatigue in Breast Cancer Patients Undergoing Radiotherapy: VibBRa Study

Purpose:

Although there is evidence that breast cancer patients benefit from exercising during treatment, exercising during radiotherapy and especially the effects on upper-limb dysfunctions have been infrequently assessed. Therefore, we primarily aimed to confirm our interventions’ feasibility and secondarily aimed to affect upper-limb dysfunctions and fatigue.

Methods:

Twenty-two breast cancer patients scheduled for radiotherapy were allocated to an intervention (IG) or a passive control group (CG) as they preferred. IG exercised 3×/week during 6 weeks of radiotherapy: cycling endurance, handheld vibration, and balance training. We documented adverse events and training compliance (feasibility) and assessed the range of shoulder motion (ROM), isometric hand grip strength, vibration sense on the first metacarpophalangeal joint of the affected upper limb, and fatigue.

Results:

We observed no adverse events and a training compliance of 98 %. IG’s ROM improved significantly (abduction: 11°; 95% confidence interval [CI] 5 to 20; external rotation: 5°, 95% CI 0 to 10), as did the hand grip strength (1.6 kg, 95% CI −0.6 to 3.1), while CG’s ROM did not change. CG’s vibration sense worsened (−1.0 points, 95% CI −1.5 to −0.5), while IG’s remained stable. Changes in general fatigue levels between IG (−2.0 points, 95% CI −3.0 to −1.0) and CG (0.5 points, 95% CI −1.0 to 4.5) revealed significant differences (P = .008)

Conclusions:

Our intervention proved to be feasible and provides novel findings: it reduced fatigue levels and interestingly, handheld vibration exercises improved upper-limb function due to shoulder ROM, hand grip strength, and vibration sense.

Balance Training Enhances Vestibular Function and Reduces Overactive Proprioceptive Feedback in Elderly

Objectives: Postural control in elderly people is impaired by degradations of sensory, motor, and higher-level adaptive mechanisms. Here, we characterize the effects of a progressive balance training program on these postural control impairments using a brain network model based on system identification techniques. Methods and Material: We analyzed postural control of 35 healthy elderly subjects and compared findings to data from 35 healthy young volunteers. Eighteen elderly subjects performed a 10 week balance training conducted twice per week. Balance training was carried out in static and dynamic movement states, on support surfaces with different elastic compliances, under different visual conditions and motor tasks. Postural control was characterized by spontaneous sway and postural reactions to pseudorandom anterior-posterior tilts of the support surface. Data were interpreted using a parameter identification procedure based on a brain network model. Results: With balance training, the elderly subjects significantly reduced their overly large postural reactions and approximated those of younger subjects. Less significant differences between elderly and young subjects' postural control, namely larger spontaneous sway amplitudes, velocities, and frequencies, larger overall time delays and a weaker motor feedback compared to young subjects were not significantly affected by the balance training. Conclusion: Balance training reduced overactive proprioceptive feedback and restored vestibular orientation in elderly. Based on the assumption of a linear deterioration of postural control across the life span, the training effect can be extrapolated as a juvenescence of 10 years. This study points to a considerable benefit of a continuous balance training in elderly, even without any sensorimotor deficits.

Impact of a 6-week non-energy-restricted ketogenic diet on physical fitness, body composition and biochemical parameters in healthy adults

BACKGROUND

The ketogenic diet (KD) is a very low-carbohydrate, high-fat and adequate-protein diet that without limiting calories induces different metabolic adaptations, eg, increased levels of circulating ketone bodies and a shift to lipid metabolism. Our objective was to assess the impact of a 6-week non-energy-restricted KD in healthy adults beyond cohorts of athletes on physical performance, body composition, and blood parameters.

METHODS

Our single arm, before-and-after comparison study consisted of a 6-week KD with a previous preparation period including detailed instructions during classes and individual counselling by a dietitian. Compliance with the dietary regimen was monitored by measuring urinary ketones daily, and 7-day food records. All tests were performed after an overnight fast: cardiopulmonary exercise testing via cycle sprioergometry, blood samples, body composition, indirect calorimetry, handgrip strength, and questionnaires addressing complaints and physical sensations.

RESULTS

Forty-two subjects aged 37 ± 12 years with a BMI of 23.9 ± 3.1 kg/m² completed the study. Urinary ketosis was detectable on 97% of the days, revealing very good compliance with the KD. Mean energy intake during the study did not change from the habitual diet and 71.6, 20.9, and 7.7% of total energy intake were from fat, protein, and carbohydrates, respectively. Weight loss was -2.0 ± 1.9 kg (P < 0.001) with equal losses of fat-free and fat mass. VO₂peak and peak power decreased from 2.55 ± 0.68 l/min to 2.49 ± 0.69 l/min by 2.4% (P = 0.023) and from 241 ± 57 W to 231 ± 57 W by 4.1% (P < 0.001), respectively, whereas, handgrip strength rose slightly from 40.1 ± 8.8 to 41.0 ± 9.1 kg by 2.5% (P = 0.047). The blood lipids TG and HDL-C remained unchanged, whereas total cholesterol and LDL-C increased significantly by 4.7 and 10.7%, respectively. Glucose, insulin, and IGF-1 dropped significantly by 3.0, 22.2 and 20.2%, respectively.

CONCLUSIONS

We detected a mildly negative impact from this 6-week non-energy-restricted KD on physical performance (endurance capacity, peak power and faster exhaustion). Our findings lead us to assume that a KD does not impact physical fitness in a clinically relevant manner that would impair activities of daily living and aerobic training. However, a KD may be a matter of concern in competitive athletes.

TRIAL REGISTRATION

DRKS00009605, registered 08 January 2016.

Implementing a home-based exercise program for patients with advanced, incurable diseases after discharge and their caregivers: lessons we have learned

BACKGROUND

Palliative care (PC) patients experience loss of physical function which usually impedes mobility, autonomy and quality of life. We aimed at examining the feasibility of a home-based exercise program for patients with advanced, incurable diseases after discharge.

RESULTS

This was a single-arm pilot study (WHO-ICTRP: DRKS00005048). The 12-week home-based program comprised strength, balance, flexibility and endurance components. Patients with a presumed life expectancy of 6-12 months were recruited during a 6-months period on a specialized PC and a radiation therapy ward. We chose the De Morton Mobility Index as primary outcome. Secondary outcomes were quality of life, 6-min walk test and others. A total of 145 patients were screened, 103 (98%) out of 105 patients on the specialized PC ward could not be included, mostly because of a low performance status [n = 94; 90%; Eastern Cooperative Oncology Group (ECOG) >2]. The only two eligible patients declined to participate. Eleven out of 40 patients (28%) were eligible on the radiation therapy ward. However, only one patient (9%) participated but dropped out 2 days later (upcoming surgery). Distance to the hospital (n = 3; 30%) and considering additional tasks as "too much" (n = 3; 30%) were most common reasons for non-participation.

CONCLUSIONS

Establishing a home-based exercise program for inpatients after discharge was not feasible mainly due to non-eligibility and lack of demand. For future trials, we suggest that choosing (1) outpatients with (2) an ECOG of ≤2 and (3) an estimated survival of ≥9 months could enhance participation in home-based exercise programs.

Balance impairments and neuromuscular changes in breast cancer patients with chemotherapy-induced peripheral neuropathy

OBJECTIVE

Chemotherapy-induced peripheral neuropathy (CIPN) is a common side effect of cancer treatment. Resulting sensory and motor dysfunctions often lead to functional impairments like gait or balance disorders. As the underlying neuromuscular mechanisms are not fully understood, we compared balance performance of CIPN patients with healthy controls (CON) to specify differences responsible for postural instability.

METHODS

20 breast cancer patients with CIPN (PAT) and 16 matched CONs were monitored regarding centre of pressure displacement (COP) and electromyographic activity of M. soleus, gastrocnemius, tibialis anterior, rectus femoris and biceps femoris. We calculated antagonistic co-contraction indices (CCI) and elicited soleus H-reflexes to evaluate changes in the elicitability and sensitivity of spinal reflex circuitry.

RESULTS

PAT's COP displacement was greater than CON's (p=.013) and correlated significantly with the level of CCIs and self-reported CIPN symptoms. PAT revealed prolonged H-wave latency (p=.021), decreased H-reflex elicitability (p=.001), and increased H-reflex sensitivity from bi- to monopedal stance (p=.004).

CONCLUSIONS

We summarise that CIPN causes balance impairments and leads to changes in elicitability and sensitivity of spinal reflex circuitry associated with postural instability. We assume that increased simultaneous antagonistic muscle activation may be used as a safety strategy for joint stiffness to compensate for neuromuscular degradation.

SIGNIFICANCE

Sensorimotor training has the potential to influence neuromuscular mechanisms in order to improve balance performance. Therefore, this training modality should be evaluated as a possible treatment strategy for CIPN.

Medium-chain acyl-CoA dehydrogenase deficiency associated with a novel splice mutation in the ACADM gene missed by newborn screening

Background

Medium-chain acyl-CoA dehydrogenase (MCAD) deficiency is the most common disorder of mitochondrial fatty acid β-oxidation and a target disease of newborn screening in many countries.

Case presentation

We report on two siblings with mild MCAD deficiency associated with a novel splice site mutation in the ACADM gene. The younger sibling was detected by newborn screening, while the older sister was missed, but diagnosed later on by genetic family testing. Both children were found to be compound heterozygous for the common c.985A > G (p.K329E) mutation and a novel splice site mutation, c.600-18G > A, in the ACADM gene. To determine the biological consequence of the c.600-18G > A mutation putative missplicing was investigated at RNA level in granulocytes and monocytes of one of the patients. The splice site mutation was shown to lead to partial missplicing of the ACADM pre-mRNA. Of three detected transcripts two result in truncated, non-functional MCAD proteins as reflected by the reduced octanoyl-CoA oxidation rate in both patients. In one patient a decrease of the octanoyl-CoA oxidation rate was found during a febrile infection indicating that missplicing may be temperature-sensitive.

Conclusions

Our data indicate that the c.600-18G > A variant activates a cryptic splice site, which competes with the natural splice site. Due to only partial missplicing sufficient functional MCAD protein remains to result in mild MCADD that may be missed by newborn screening.

Electronic supplementary material

The online version of this article (doi:10.1186/s12881-015-0199-5) contains supplementary material, which is available to authorized users.

Relationship between strength, balance and mobility in children aged 7-10 years

The purpose of this study was to investigate the association between variables of lower extremity muscle strength, balance, and mobility assessed under various task conditions. Twenty-one healthy children (mean age: 9±1 years) were tested for their isometric and dynamic strength as well as for their steady-state, proactive, and reactive balance and mobility. Balance and mobility tests were conducted under single and dual task conditions. Significant positive correlations were detected between measures of isometric and dynamic leg muscle strength. Hardly any significant associations were observed between variables of strength and balance/mobility and between measures of steady-state, proactive, and reactive balance. Additionally, no significant correlations were detected between balance/mobility tests performed under single and dual task conditions. The predominately non-significant correlations between different balance components and mobility imply that balance and mobility performance is task specific. Further, strength and balance/mobility as well as balance under single and dual task conditions seem to be independent of each other and may have to be tested and trained complementarily.

Effects of muscle fatigue on gait characteristics under single and dual-task conditions in young and older adults

BACKGROUND

Muscle fatigue and dual-task walking (e.g., concurrent performance of a cognitive interference (CI) while walking) represent major fall risk factors in young and older adults. Thus, the objectives of this study were to examine the effects of muscle fatigue on gait characteristics under single and dual-task conditions in young and older adults and to determine the impact of muscle fatigue on dual-task costs while walking.

METHODS

Thirty-two young (24.3 ± 1.4 yrs, n = 16) and old (71.9 ± 5.5 yrs, n = 16) healthy active adults participated in this study. Fatigue of the knee extensors/flexors was induced by isokinetic contractions. Subjects were tested pre and post fatigue, as well as after a 5 min rest. Tests included the assessment of gait velocity, stride length, and stride length variability during single (walking), and dual (CI+walking) task walking on an instrumented walkway. Dual-task costs while walking were additionally computed.

RESULTS

Fatigue resulted in significant decreases in single-task gait velocity and stride length in young adults, and in significant increases in dual-task gait velocity and stride length in older adults. Further, muscle fatigue did not affect dual-task costs during walking in young and older adults. Performance in the CI-task was improved in both age groups post-fatigue.

CONCLUSIONS

Strategic and/or physiologic rationale may account for the observed differences in young and older adults. In terms of strategic rationale, older adults may walk faster with longer strides in order to overcome the feeling of fatigue-induced physical discomfort as quickly as possible. Alternatively, older adults may have learned how to compensate for age-related and/or fatigue-induced muscle deficits during walking by increasing muscle power of synergistic muscle groups (e.g., hip flexors). Further, a practice and/or learning effect may have occurred from pre to post testing. Physiologic rationale may comprise motor unit remodeling in old age resulting in larger proportions of type I fibres and thus higher fatigue-resistance and/or increased muscle spindle sensitivity following fatigue leading to improved forward propulsion of the body. These findings are preliminary and have to be confirmed by future studies.

Einfluss der Aufgabenpriorisierung auf die Haltungskontrolle unter Doppeltätigkeitsbedingung

Zusammenfassung. Gegenstand der Studie war die Überprüfung des Einflusses der Aufgabenpriorisierung auf die Haltungskontrolle unter Doppeltätigkeitsbedingung. Hierzu wurden bei jungen und gesunden Erwachsenen (N = 60) das Gleichgewicht und die Leistung beim Rückwärtsrechnen einzeln (Einfachtätigkeit) sowie simultan (Doppeltätigkeit) unter drei verschiedenen Priorisierungsbedingungen getestet. In der ersten Bedingung sollte die Aufmerksamkeit auf die Gleichgewichtsaufgabe (Gruppe: „Stehen”) und in der zweiten Bedingung auf die kognitive Aufgabe (Gruppe: „Rechnen”) gerichtet werden. In der dritten Bedingung sollte eine Aufmerksamkeitslenkung auf beide Aufgaben erfolgen (Gruppe: „Stehen+Rechnen”). Im Ergebnis zeigten sich weder im Schwankungsverhalten noch in der Rechenleistung statistisch signifikante Gruppenunterschiede. Diese Befunde sind konsistent mit Studien, in denen gleiche motorische, aber andere kognitive Aufgaben verwendet wurden, was auf das Vorliegen eines relativ robusten Phänomens hindeutet. Da Personen in alltäglichen Doppeltätigkeitssituationen bestrebt sind, beide Aufgaben bestmöglich auszuführen, sollte insbesondere in Testsituationen mit funktioneller Relevanz der Priorisierung beider Aufgaben Vorzug gegenüber einer anderen Aufmerksamkeitslenkung gegeben werden.

Pharmacokinetics of meropenem in critically ill patients with acute renal failure treated by continuous hemodiafiltration

The pharmacokinetics of meropenem were studied in nine anuric critically ill patients treated by continuous venovenous hemodiafiltration. Peak levels after infusion of 1,000 mg over 30 min amounted to 103.2 +/- 45.9 microgram/ml, and trough levels at 12 h were 9.6 +/- 3.8 microgram/ml. A dosage of 1,000 mg of meropenem twice a day provides plasma drug levels covering intermediately susceptible microorganisms. Further reductions of the dosage might be appropriate for highly susceptible bacteria or when renal replacement therapies with lower clearances are applied.