Firefighters muscular recovery after a heavy work bout in the heat

Skeletal muscle fitness and physiology as determinants of firefighter performance and safety: a narrative review

Firefighters routinely perform tasks that are reliant on their muscular fitness, which includes muscular strength, power and endurance. Separately, firefighters can present with unique skeletal muscle physiology characteristics due to the strenuous nature of this occupation. This review aims to summarise muscular fitness and physiology as determinants of a firefighter's ability to perform occupation-specific tasks, identify the relevance of both muscular fitness and physiology to a firefighter's risk for sustaining a work-related injury, and address the contributions of muscular fitness and physiology on a firefighter's ability to recover from tasks and their readiness for performing subsequent or future tasks. The presented evidence reveals muscular fitness can determine a firefighter's capacity to perform their job effectively, while also influencing risk for occupational injury. Collectively, this review indicates exercise training emphasising improvements in muscular strength, power, and endurance (i.e. resistance training) should be encouraged in this occupation.

Relationship between postural stability and fall risk in young adult after lower limb muscle fatigue

Introduction: Muscle fatigue can reduce body balance and activity of daily living tasks. Therefore, this study aims to identify the correlation between postural stability and fall risk due to muscle fatigue. The components in postural stability include Overall Stability Index (OSI), Anterior-Posterior Stability Index (APSI), and Mediolateral Stability Index (MLSI). Design and Methods: A total of seven healthy adults aged 31.1±7.4 years were recruited in this study. The sit-to-stand (STS) protocol was used to induce lower limb muscle fatigue, while postural stability and fall risk were assessed using the Biodex Balance System (BBS) before and after muscle fatigue. Result: The result showed a significant increase in postural stability index after fatigue only for OSI with p<0.05, while no significant difference was found on APSI and MLSI with p=0.157 and p=0.109 respectively. However, the mean score for the postural stability index showed an increase in percentage with 47.8% in OSI, 26.3% in APSI and 46.8% in MLSI.  Furthermore,fall risk showed no significant differences with p=0.149, but the mean score data increased by 16.7% after fatigue. The correlation between fall risk and OSI was significant with p<0.05, while MLSI had a significant negative correlation with APSI (p<0.05). Conclusions: Based on the results, the young adults had reduced overall postural stability but were less affected by fall risk after muscle fatigue. The positive correlation between OSI and fall risk indicated that their overall postural stability can induce the fall risk after muscle fatigue. Therefore, young adults need to be aware of their fatigue symptoms during prolonged exercise that can increase fall risk potential.

Occupational heat strain in outdoor workers: A comprehensive review and meta-analysis

The present comprehensive review (i) summarizes the current knowledge on the impacts of occupational heat stress on outdoor workers, (ii) provides a historical background on this issue, (iii) presents a meta-analysis of published data, (iv) explores inter-individual and intra-individual factors, (v) discusses the available heat mitigation strategies, (vi) estimates physical work capacity, labour productivity, and metabolic rate for the year 2030, and (vii) provides an overview of existing policy and legal frameworks on occupational heat exposure. Meta-analytic findings from 38 field studies that involved monitoring 2,409 outdoor workers across 41 jobs in 21 countries suggest that occupational heat stress increases the core (r = 0.44) and skin (r = 0.44) temperatures, as well as the heart rate (r = 0.38) and urine specific gravity (r = 0.13) of outdoor workers (all p < 0.05). Moreover, it diminishes the capacity of outdoor workers for manual labour (r = -0.82; p < 0.001) and is responsible for more than two thirds of the reduction in their metabolic rate. Importantly, our analysis shows that physical work capacity is projected to be highly affected by the ongoing anthropogenic global warming. Nevertheless, the metabolic rate and, therefore, labour productivity are projected to remain at levels higher than the workers' physical work capacity, indicating that people will continue to work more intensely than they should to meet their financial obligations for food and shelter. In this respect, complementary measures targeting self-pacing, hydration, work-rest regimes, ventilated garments, and mechanization can be adopted to protect outdoor workers.

Effects of a capacitive-resistive electric transfer therapy on physiological and biomechanical parameters in recreational runners: A randomized controlled crossover trial

OBJECTIVES

This study compared the effects of a capacitive-resistive electric transfer therapy (Tecar) and passive rest on physiological and biomechanical parameters in recreational runners when performed shortly after an exhausting training session.

DESIGN

Randomized controlled crossover trial.

SETTING

University biomechanical research laboratory.

PARTICIPANTS

Fourteen trained male runners MAIN OUTCOME MEASURES: Physiological (running economy, oxygen uptake, respiratory exchange ratio, ventilation, heart rate, blood lactate concentration) and biomechanical (step length; stride angle, height, frequency, and contact time; swing time; contact phase; support phase; push-off phase) parameters were measured during two incremental treadmill running tests performed two days apart after an exhaustive training session.

RESULTS

When running at 14 km/h and 16 km/h, the Tecar treatment group presented greater increases in stride length (p < 0.001), angle (p < 0.05) and height (p < 0.001) between the first and second tests than the control group and, accordingly, greater decreases in stride frequency (p < 0.05). Physiological parameters were similar between groups.

CONCLUSIONS

The present study suggests that a Tecar therapy intervention enhances biomechanical parameters in recreational runners after an exhaustive training session more than passive rest, generating a more efficient running pattern without affecting selected physiological parameters.

Autonomy and Firefighting: Perceived Competence and Stress

OBJECTIVE

In workplace settings, autonomy is implicated in employee motivation as well as supervisor autonomy support. As a profession of risk, firefighters may experience greater levels of stress.

METHODS

A self-determination paradigm was applied to the firefighter workplace. Of particular interest were perceived competence (to perform job duties) and the experience of stress. Firefighters' levels of autonomous and controlled regulation were surveyed, along with their perceptions of the autonomy support of their immediate supervisor.

RESULTS

Autonomous regulation was positively related to perceived competence, whereas controlled regulation was negatively related. Higher levels of controlled regulation were also connected with greater stress. In contrast, greater perceived autonomy support was associated with decreased stress.

CONCLUSIONS

Both perceived competence and stress are related to firefighter motivation and autonomy support. Recommendations are offered to increase autonomy support by chief officers.

Recovery of gait after quadriceps muscle fatigue

The aim of this study was to investigate the effect of recovery time after quadriceps muscle fatigue on gait in young adults. Forty young adults (20-40 years old) performed three 8-m gait trials at preferred velocity before and after muscle fatigue, and after 5, 10 and 20min of passive rest. In addition, at each time point, two maximal isometric voluntary contractions were preformed. Muscle fatigue was induced by repeated sit-to-stand transfers until task failure. Spatio-temporal, kinetic and muscle activity parameters, measured in the central stride of each trial, were analyzed. Data were compared between before and after the muscle fatigue protocol and after the recovery periods by one-way repeated measures ANOVA. The voluntary force was decreased after the fatigue protocol (p<0.001) and after 5, 10 and 20min of recovery compared to before the fatigue protocol. Step width (p<0.001) and RMS of biceps femoris (p<0.05) were increased immediately after the fatigue protocol and remained increased after the recovery periods. In addition, stride duration was decreased immediately after the fatigue protocol compared to before and to after 10 and 20min of rest (p<0.001). The anterior-posterior propulsive impulse was also decreased after the fatigue protocol (p<0.001) and remained low after 5, 10 and 20min of rest. We conclude that 20min is not enough to see full recovery of gait after exhaustive quadriceps muscle fatigue.

Multivariate statistical assessment of predictors of firefighters' muscular and aerobic work capacity

Physical capacity has previously been deemed important for firefighters physical work capacity, and aerobic fitness, muscular strength, and muscular endurance are the most frequently investigated parameters of importance. Traditionally, bivariate and multivariate linear regression statistics have been used to study relationships between physical capacities and work capacities among firefighters. An alternative way to handle datasets consisting of numerous correlated variables is to use multivariate projection analyses, such as Orthogonal Projection to Latent Structures. The first aim of the present study was to evaluate the prediction and predictive power of field and laboratory tests, respectively, on firefighters’ physical work capacity on selected work tasks. Also, to study if valid predictions could be achieved without anthropometric data. The second aim was to externally validate selected models. The third aim was to validate selected models on firefighters’ and on civilians’. A total of 38 (26 men and 12 women) + 90 (38 men and 52 women) subjects were included in the models and the external validation, respectively. The best prediction (R²) and predictive power (Q²) of Stairs, Pulling, Demolition, Terrain, and Rescue work capacities included field tests (R² = 0.73 to 0.84, Q² = 0.68 to 0.82). The best external validation was for Stairs work capacity (R² = 0.80) and worst for Demolition work capacity (R² = 0.40). In conclusion, field and laboratory tests could equally well predict physical work capacities for firefighting work tasks, and models excluding anthropometric data were valid. The predictive power was satisfactory for all included work tasks except Demolition.

Laboratory or field tests for evaluating firefighters' work capacity?

Muscle strength is important for firefighters work capacity. Laboratory tests used for measurements of muscle strength, however, are complicated, expensive and time consuming. The aims of the present study were to investigate correlations between physical capacity within commonly occurring and physically demanding firefighting work tasks and both laboratory and field tests in full time (N = 8) and part-time (N = 10) male firefighters and civilian men (N = 8) and women (N = 12), and also to give recommendations as to which field tests might be useful for evaluating firefighters' physical work capacity. Laboratory tests of isokinetic maximal (IM) and endurance (IE) muscle power and dynamic balance, field tests including maximal and endurance muscle performance, and simulated firefighting work tasks were performed. Correlations with work capacity were analyzed with Spearman's rank correlation coefficient (rs). The highest significant (p<0.01) correlations with laboratory and field tests were for Cutting: IE trunk extension (rs = 0.72) and maximal hand grip strength (rs = 0.67), for Stairs: IE shoulder flexion (rs = -0.81) and barbell shoulder press (rs = -0.77), for Pulling: IE shoulder extension (rs = -0.82) and bench press (rs = -0.85), for Demolition: IE knee extension (rs = 0.75) and bench press (rs = 0.83), for Rescue: IE shoulder flexion (rs = -0.83) and bench press (rs = -0.82), and for the Terrain work task: IE trunk flexion (rs = -0.58) and upright barbell row (rs = -0.70). In conclusion, field tests may be used instead of laboratory tests. Maximal hand grip strength, bench press, chin ups, dips, upright barbell row, standing broad jump, and barbell shoulder press were strongly correlated (rs≥0.7) with work capacity and are therefore recommended for evaluating firefighters work capacity.