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Fatiguing handgrip exercise alters maximal force-generating capacity of plantar-flexors
Exercise-induced fatigue causes changes within the central nervous system that decrease force production capacity in fatigued muscles. The impact on unrelated, non-exercised muscle performance is still unclear. The primary aim of this study was to examine the impact of a bilateral forearm muscle contraction on the motor function of the distal and unrelated ankle plantar-flexor muscles. The secondary aim was to compare the impact of maximal and submaximal forearm contractions on the non-fatigued ankle plantar-flexor muscles. Maximal voluntary contractions (MVC) of the forearm and ankle plantar-flexor muscles as well as voluntary activation (VA) and twitch torque of the ankle plantar-flexor muscles were assessed pre-fatigue and throughout a 10-min recovery period. Maximal (100 % MVC) and submaximal (30 % MVC) sustained isometric handgrip contractions caused a decreased handgrip MVC (to 49.3 ± 15.4 and 45.4 ± 11.4 % of the initial MVC for maximal and submaximal contraction, respectively) that remained throughout the 10-min recovery period. The fatigue protocols also caused a decreased ankle plantar-flexor MVC (to 77 ± 8.3 and 92.4 ± 6.2 % of pre-fatigue MVC for maximal and submaximal contraction, respectively) and VA (to 84.3 ± 15.7 and 97.7 ± 16.1 % of pre-fatigue VA for maximal and submaximal contraction, respectively). These results suggest central fatigue created by the fatiguing handgrip contraction translated to the performance of the non-exercised ankle muscles. Our results also show that the maximal fatigue protocol affected ankle plantar-flexor MVC and VA more severely than the submaximal protocol, highlighting the task-specificity of neuromuscular fatigue.
Journal Article
Secrets of the human body
\"206 bones. One heart. Two eyes. Ten fingers. What makes tears of joy different from tears of sadness? Why is a gut feeling so much smarter than you think? And why is 90% of you not even human? You may think you know the human body--heart, lungs, brain and bones--but our bodies are full of extraordinary mysteries that science is only just beginning to understand. This book will change forever how we think about our bodies. Thanks to cutting-edge science and cutting-edge technology we get a tantalizing glimpse beneath our skin, and there we see the secrets that make every ordinary human body ... extraordinary.\"--Page 4 of cover.
Book
Viral reactivations following hematopoietic stem cell transplantation in pediatric patients - A single center 11-year analysis
Viral reactivation occurs frequently in the context of immunodeficiency and immunosuppression after allogeneic hematopoietic stem cell transplantation (allo-HSCT) and can cause severe complications. The aim of this single-center retrospective analysis was to characterize viral infections in the first year after HSCT, to investigate risk factors and to study the impact of viral infections on transplantation outcome. This will facilitate the identification of at-risk patients and the development of new preventive strategies. 107 pediatric allo-HSCT from January 2005 through December 2015 were analyzed for infections with Epstein-Barr virus (EBV), cytomegalovirus (CMV), human herpesvirus 6 (HHV-6), adenovirus (ADV), herpes simplex virus (HSV) and varicella zoster virus (VZV). Viral infections were detected after 68.2% of transplantations. The viruses most commonly encountered were HHV-6 (36/107) and EBV (30/107). Severe viral disease was rare (7/107) and none of the patients died as result of viral reactivation. Important risk factors for viral infections were higher age at HSCT, donor type and occurrence of acute graft-versus-host disease (aGvHD). Especially for EBV, transplant from an unrelated donor and in-vivo T-cell depletion (TCD) had a significant effect on infection rates, whereas for CMV the strongest effect was seen by donor and recipient serostatus with recipient seropositivity most predictive for reactivation. The occurrence of severe aGvHD was associated with EBV and ADV infections. For HSV, the recipient serostatus was identified as prognostic factor for HSV infections, while we found higher age at time of HSCT as risk factor for VZV infections. The overall survival of patients with or without viral infections did not differ significantly. Interestingly, when looking at the 85 patients in our cohort who had received an HSCT for a malignant disease, a tendency towards lower relapse rates was seen in patients affected by viral infections (HR 0.51, 95% CI 0.25 - 1.06, p = 0.072). Viral reactivations are common after pediatric allo-HSCT, though severe complications were rare in our collective. Determining risk factors for viral reactivations may help to identify patients in need of intensified monitoring and to individualize preventive strategies.
Journal Article
Management of herpesvirus reactivations in patients with solid tumours and hematologic malignancies: update of the Guidelines of the Infectious Diseases Working Party (AGIHO) of the German Society for Hematology and Medical Oncology (DGHO) on herpes simplex virus type 1, herpes simplex virus type 2, and varicella zoster virus
Clinical reactivations of herpes simplex virus or varicella zoster virus occur frequently among patients with malignancies and manifest particularly as herpes simplex stomatitis in patients with acute leukaemia treated with intensive chemotherapy and as herpes zoster in patients with lymphoma or multiple myeloma. In recent years, knowledge on reactivation rates and clinical manifestations has increased for conventional chemotherapeutics as well as for many new antineoplastic agents. This guideline summarizes current evidence on herpesvirus reactivation in patients with solid tumours and hematological malignancies not undergoing allogeneic or autologous hematopoietic stem cell transplantation or other cellular therapy including diagnostic, prophylactic, and therapeutic aspects. Particularly, strategies of risk adapted pharmacological prophylaxis and vaccination are outlined for different patient groups. This guideline updates the guidelines of the Infectious Diseases Working Party (AGIHO) of the German Society for Hematology and Medical Oncology (DGHO) from 2015 “Antiviral prophylaxis in patients with solid tumours and haematological malignancies” focusing on herpes simplex virus and varicella zoster virus.
Journal Article
Physiological and molecular responses to an acute bout of reduced-exertion high-intensity interval training (REHIT)
Purpose
We have previously shown that 6 weeks of reduced-exertion high-intensity interval training (REHIT) improves
V
˙
O
2
max in sedentary men and women and insulin sensitivity in men. Here, we present two studies examining the acute physiological and molecular responses to REHIT.
Methods
In Study 1, five men and six women (age: 26 ± 7 year, BMI: 23 ± 3 kg m
−2
,
V
˙
O
2
max: 51 ± 11 ml kg
−1
min
−1
) performed a single 10-min REHIT cycling session (60 W and two 20-s ‘all-out’ sprints), with
vastus lateralis
biopsies taken before and 0, 30, and 180 min post-exercise for analysis of glycogen content, phosphorylation of AMPK, p38 MAPK and ACC, and gene expression of PGC1α and GLUT4. In Study 2, eight men (21 ± 2 year; 25 ± 4 kg·m
−2
; 39 ± 10 ml kg
−1
min
−1
) performed three trials (REHIT, 30-min cycling at 50 % of
V
˙
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2
max, and a resting control condition) in a randomised cross-over design. Expired air, venous blood samples, and subjective measures of appetite and fatigue were collected before and 0, 15, 30, and 90 min post-exercise.
Results
Acutely, REHIT was associated with a decrease in muscle glycogen, increased ACC phosphorylation, and activation of PGC1α. When compared to aerobic exercise, changes in
V
˙
O
2
, RER, plasma volume, and plasma lactate and ghrelin were significantly more pronounced with REHIT, whereas plasma glucose, NEFAs, PYY, and measures of appetite were unaffected.
Conclusions
Collectively, these data demonstrate that REHIT is associated with a pronounced disturbance of physiological homeostasis and associated activation of signalling pathways, which together may help explain previously observed adaptations once considered exclusive to aerobic exercise.
Journal Article
Mechanisms of force depression caused by different types of physical exercise studied by direct electrical stimulation of human quadriceps muscle
Purpose
Force production frequently remains depressed for several hours or even days after various types of strenuous physical exercise. We hypothesized that the pattern of force changes during the first hour after exercise can be used to reveal muscular mechanisms likely to underlie the decline in muscle performance during exercise as well as factors involved in the triggering the prolonged force depression after exercise.
Methods
Nine groups of recreationally active male volunteers performed one of the following types of exercise: single prolonged or repeated short maximum voluntary contractions (MVCs); single or repeated all-out cycling bouts; repeated drop jumps. The isometric force of the right quadriceps muscle was measured during stimulation with brief 20 and 100 Hz trains of electrical pulses given before and at regular intervals for 60 min after exercise.
Results
All exercises resulted in a prolonged force depression, which was more marked at 20 Hz than at 100 Hz. Short-lasting (≤2 min) MVC and all-out cycling exercises showed an initial force recovery (peak after ~ 5 min) followed by a secondary force depression. The repeated drop jumps, which involve eccentric contractions, resulted in a stable force depression with the 20 Hz force being markedly more decreased after 100 than 10 jumps.
Conclusions
In accordance with our hypothesis, the results propose at least three different mechanisms that influence force production after exercise: (1) a transiently recovering process followed by (2) a prolonged force depression after metabolically demanding exercise, and (3) a stable force depression after mechanically demanding contractions.
Journal Article