Does fatigue influence joint-specific work and ground force production during the first steps of maximal acceleration?

During initial acceleration, the first steps of a maximal-effort (sprint) run often determine success or failure in the capture and evasion of an opponent, and is therefore a vital factor of success in many modern sports. However, accelerative events are commonly performed after having already run considerable distances, and the associated fatigue should impair muscle force production and thus reduce acceleration. Despite this, the effects of running-induced fatigue on our ability to accelerate as well as the running technique used to achieve it have received little attention. We recorded 3-D kinematics and ground reaction forces during the first three steps of the acceleration phase from a standing start before and after performing a high-speed, multi-directional, fatiguing run-walk protocol in well-trained running athletes who were habituated to accelerative sprinting. We found that the athletes were able to maintain their acceleration despite changing running technique, which was associated with use of a more upright posture, longer ground contact time, increased vertical ground reaction impulse, decreased hip flexion and extension velocities, and a shift in peak joint moments, power, and positive work from the hip to the knee joint; no changes were detected in ankle joint function. Thus, a compensatory increase in knee joint function alleviated the reduction in hip flexor-extensor capacity. These acute adaptations may indicate that the hip extensors (gluteal and hamstring muscle groups) were more susceptible to fatigue than the ankle and knee musculature, and may thus be a primary target for interventions promoting fatigue resistance.

Fatigue does not increase limb asymmetry or induce proximal joint power shift in habitual, multi-speed runners.

During prolonged jogging, joint moment and work tend to decrease in the distal (ankle) joint but increase at proximal (hip/knee) joints as performance fatigue manifests, and such adaptations might be expected to occur in sprinting. Fatigue is also thought to increase inter-limb asymmetries, which is speculated to influence injury risk. However, the effects of fatigue on sprint running gait have been incompletely studied, so these hypotheses remain untested. Using statistical parametric mapping, we compared 3-D kinematics and ground reaction force production between the dominant (DL) and non-dominant (NDL) legs of 13 soccer players during both non-fatigued and fatigued sprint running. Contrary to the tested hypotheses, relative between-leg differences were greater in non-fatigued than fatigued sprinting. DL generated higher propulsive impulse due to increased ankle work, while NDL exhibited greater vertical impulse, potentially due to greater hip flexion prior to downward foot acceleration. Whilst few changes were detected in DL once fatigued, NDL shifted towards greater horizontal force production, largely resulting from an increase in plantar flexion (distal-joint) moments and power. After fatiguing running, inter-limb asymmetry was reduced and no distal-to-proximal shift in joint work was detected. These adaptations may attenuate decreases in running speed whilst minimising injury risk.

The multidimensional sleep health of individuals with multiple sclerosis and Huntington's disease and healthy controls.

STUDY OBJECTIVES: Sleep issues are common for people with neurodegenerative conditions, yet research has focused on specific aspects of sleep. While important, a more holistic approach to investigating sleep, termed "sleep health," considers sleep's positive and negative aspects. Current studies exploring sleep health have lacked a control group for reference. For the first time, this study investigated the sleep health of people living with multiple sclerosis and Huntington's disease (HD) and compared it with a community sample. METHODS: 111 people, including 43 with multiple sclerosis, 19 with HD, and 49 from a community sample, participated in this study. The data, including actigraphy, Pittsburgh Sleep Quality Index, and Epworth Sleepiness Scale, were collected as part of ongoing research studies. Seven sleep health domains were determined from the collected data, and a composite sleep health score was developed. Analysis of variance and independent t tests were performed to identify population and sex differences. RESULTS: The HD group had higher sleep regularity and lower sleep rhythmicity than the multiple sclerosis and community sample groups. The HD group had significantly less sleep duration than the multiple sclerosis group. No significant differences between the groups were observed in the sleep health composite score. Males had significantly higher sleep regularity within the HD group but significantly lower sleepiness scores in the community sample. CONCLUSIONS: These findings indicate that people with HD may experience greater variance in their wake times, therefore decreasing the consistency of being awake or asleep 24 hours apart. Understanding the mechanisms for this should be explored in people with HD. CITATION: Turner M, Griffiths M, Laws M, Vial S, Bartlett D, Cruickshank T. The multidimensional sleep health of individuals with multiple sclerosis and Huntington's disease and healthy controls. J Clin Sleep Med. 2024;20(6):967-972.

Effect of physical activity during COVID-19 on the sleep health of community-level athletes in Australia.

The COVID-19 outbreak presents a serious health challenges, with Australia enforcing tight restrictions, impacting sporting activities and sleep health of many Australians. Routine lifestyle patterns (physical activity and employment) are important to maintaining overall sleep health. Current literature indicates COVID-19 pandemic negatively affected the employment status and sport engagement. The aim of this study was to explore the effect of physical activity during COVID-19 on sleep health, and its association with employment and sport engagement of community-level athletes throughout Australia. Participants self-reported sleep health prior to COVID-19 (pre-sleep) and over the month prior to data collection (during-sleep) using the validated 5-item Satisfaction Alertness Timing Efficiency and Duration questionnaire (SATED). Wilcoxon Signed Rank Test assessed the difference in pre- and during perceived sleep health scores. A generalized linear model was used to assess the impact of sporting and demographic factors on a community athlete's change in perceived sleep health score. A total of 139 community-level Australian athletes responded. The majority of participants were aged 18-30 and engaged in full-time employment prior to COVID-19 (n = 82, 54%). Eight percent of participants were unemployed prior to the COVID-19 pandemic (n = 12, 8%). Our findings show that sleep health values were higher during COVID-19, with 91.4% of respondents able to maintain some form of physical activity during the pandemic. Together, our results show better sleep health scores reported by the respondents who maintained or lost employment and maintained sporting engagements during the pandemic.

A Survey to Evaluate the Association of COVID-19 Restrictions on Perceived Mood and Coping in Australian Community Level Athletes.

Highlights: No differences in coping or well-being in Australian community athletes based on the level of support received during COVID-19 restrictions.Community level athletes had better coping when a training program was provided.No difference between individual or team community athletes for well-being or coping scores. Australian community level athletes faced unprecedented changes to their training and competition options as the global COVID-19 pandemic took a stronghold. This disruption was predicted to have a negative impact on emotional well-being as communities braced through periods of social isolation and physical distancing requirements. This study provides an Australian perspective on the emotional well-being of community level athletes and the extent to which they coped during the COVID-19 pandemic. Emotional well-being and coping were measured using the Brief Emotional Experience Scale and the 28-item Brief Cope Scale. Both instruments were administered along with other questions pertaining to participant demographics and training status via an online survey between April and June 2020. The survey was disseminated to community athletes through word-of-mouth and social media platforms. No significant differences in emotional well-being were observed between athlete groups as a result of COVID-19 and its associated restrictions. Coping scores also appeared to be preserved in Australian community athletes, which contrasts the impact expected as a result of the COVID-19 pandemic. While tentative, the observed preservation in coping may have buffered potential declines in emotional well-being, which has been documented in professional and semi-professional athletes and the general population. These unexpected findings and tentative suppositions warrant further investigation and highlight the importance of conducting a country- or region-specific approach to examining the impact of COVID-19 on community athletes, as responses to COVID-19 are undoubtedly not consistent throughout the world.