Journal of Functional Morphology and Kinesiology最新文献

The aim was to identify if surface electromyography (sEMG) parameters are indicative of post-activation potentiation (PAP)/post-activation performance enhancement (PAPE), in terms of twitch potentiation and voluntary performance. Three databases were used in April 2024, with the following inclusion criteria: (a) original research, assessed in healthy human adults, and (b) sEMG parameters were measured. The exclusion criteria were (a) studies with no PAP/PAPE protocol and (b) non-randomized control trials. The following data were extracted: study characteristics/demographics, PAP/PAPE protocols, sEMG parameters, twitch/performance outcomes, and study findings. A modified physiotherapy evidence database (PEDro) scale was used for quality assessment. Fifteen randomized controlled trials (RCTs), with a total of 199 subjects, were included. The M-wave amplitude (combined with a twitch torque outcome) was shown to generally be indicative of PAP. The sEMG amplitudes (in some muscles) were found to be indicative of PAPE during ballistic movements, while a small decrease in the MdF (in certain muscles) was shown to reflect PAPE. Changes in the H_max/M_max ratio were found to contribute (temporally) to PAP, while the H-reflex amplitude was shown to be neither indicative of PAP nor PAPE. This review provides preliminary findings suggesting that certain sEMG parameters could be indicative of PAP/PAPE. However, due to limited studies, future research is warranted.

The fire service suffers from high rates of cardiovascular disease and poor overall health, and firefighters often suffer fatal and non-fatal injuries while on the job. Most fatal injuries result from sudden cardiac death, while non-fatal injuries are to the musculoskeletal system. Previous works suggest a mechanistic link between several health and performance variables and injury risk. In addition, studies have suggested physical activity and nutrition can improve overall health and occupational performance. This review offers practical applications for exercise via feasible training modalities as well as nutritional recommendations that can positively impact performance on the job. Time-efficient training modalities like high-intensity interval training and feasible modalities such as resistance training offer numerous benefits for firefighters. Also, modifying and supplementing the diet and can be advantageous for health and body composition in the fire service. Firefighters have various schedules, making it difficult for planned exercise and eating while on shift. The practical training and nutritional aspects discussed in this review can be implemented on-shift to improve the overall health and performance in firefighters.

The strength of the shoulder musculature involved with internal rotation and arm extension plays an important role in the overhead throwing motion for baseball athletes, both for throwing-related performance and injury risk. The maintenance of shoulder strength is a high priority for baseball athletes throughout a season; however, little is known in regards to the expected changes in strength throughout a season. To examine pre-post changes in shoulder strength, lower body power, and body composition among collegiate baseball players after the completion of a summer baseball league season. Amateur baseball players (n = 12; age: 20.9 ± 1.0 years.; height: 181.6 ± 5.6 cm; body mass: 86.4 ± 11.1 kg; BMI: 26.0 ± 2.6 kg/m²) participated in the current study. Pre- and post-competitive season, the participants completed shoulder strength assessments and body composition and countermovement vertical jump (CMJ) tests. An upper-body isometric test (athletic shoulder [ASH] test) was used to evaluate shoulder strength for each arm. Each subject completed maximal isometric contractions for both the throwing and non-throwing arms at four separate angles of abduction (180°, 'I'; 135°, 'Y'; 90°, 'T'; and -180°, 'A') while lying in a prone position. For shoulder strength, the primary dependent variable of interest was a composite measure that represented the average of the forces produced across all four positions of the ASH test (I, Y, T, A). For the ASH test composite measure, there was a trend toward a significant arm-by-time interaction effect (p = 0.08), as shoulder strength decreased by 9.03% for the throwing arm (ES = 0.72; 95% CI = [-0.27, -0.01]), compared to only 2.03% for the non-throwing arm (ES = 0.15; 95% CI = [-0.16, 0.09]), over the course of the season. The main effects of time (p = 0.16) and arm (p = 0.58) were not significant for the ASH test composite measure. There was no relationship between lower body power and throwing arm strength at baseline (r = 0.20, p = 0.56), and only a non-significant weak relationship at post-test (r = 0.28, p = 0.41). Throughout a season, baseball players may experience reductions in shoulder strength of the throwing arm with minimal changes in shoulder strength in the non-throwing arm.

Cardiac deaths account for the largest share of on-duty firefighter deaths. To help ensure duty fitness and minimize injury risk, many fire departments require the passing of an annual physical ability test, consisting of a battery of simulated fire suppression activities (sFSAs). The purpose of the study was to determine the relationship of sFSA performance to acute cardiac and respiratory events (ACREs) and the effect that estimated VO₂max has on sFSA performance. The study was retrospective. As part of an annual physical ability test, five timed sFSAs were performed, summed for a composite time, and categorized into three performance levels (fast, moderate, and slow). Estimated VO₂max was determined using the Forestry Step Test. A significant (p = 0.023) linear trend was observed with higher sFSA performance times being associated with a higher proportion of firefighters going on to suffer an ACRE. The estimated VO₂max was significantly (p < 0.001) higher in the fast group compared to the slow group. There was not a significant (p = 0.70) difference in estimated VO₂max between the moderate and slow groups. Estimated VO₂max performance and sFSA performance were significantly correlated, with r_s(488) = -0.272 and p < 0.001. Poorer sFSA performance was found to be associated with a higher proportion of ACREs. The results suggest that sFSA performance may be a valid indicator of ACRE injury risk and aerobic capacity.

Hypoxia increases inspiratory muscle work and consequently contributes to a reduction in exercise performance. We evaluate the effects of inspiratory muscle warm-up (IMW) on a 10 km cycling time trial in normoxia (NOR) and hypoxia (HYP). Eight cyclists performed four time trial sessions, two in HYP (FiO₂: 0.145) and two in NOR (FiO₂: 0.209), of which one was with IMW (set at 40% of maximal inspiratory pressure-MIP) and the other was with the placebo effect (PLA: set at 15% MIP). Time trials were unchanged by IMW (NOR_IMW: 893.8 ± 31.5 vs. NOR_PLA: 925.5 ± 51.0 s; HYP_IMW: 976.8 ± 34.2 vs. HYP_PLA: 1008.3 ± 56.0 s; p > 0.05), while ventilation was higher in HYP_IMW (107.7 ± 18.3) than HYP_PLA (100.1 ± 18.9 L.min^-1; p ≤ 0.05), and SpO₂ was lower (HYP_IMW: 73 ± 6 vs. HYP_PLA: 76 ± 6%; p ≤ 0.05). A post-exercise-induced reduction in inspiratory strength was correlated with exercise elapsed time during IMW sessions (HYP_IMW: r = -0.79; p ≤ 0.05; NOR_IMW: r = -0.70; p ≤ 0.05). IMW did not improve the 10 km time trial performance under normoxia and hypoxia.

Early childhood is a critical period for physical and motor development with implications for long-term health. This systematic review examined the relationship between anthropometric characteristics and measures of physical fitness and motor skills in preschool-aged children (typically 2-6 years). The search strategy was applied in four databases (PubMed, ProQuest Central, Scopus, and Web of Science) to find articles published before 11 April 2024. The results consistently demonstrated significant associations between anthropometric variables (height, weight, body mass index [BMI], body composition) and physical performance measures. Notably, height and mass were often better predictors of fitness status than BMI alone. Indicators of undernutrition (stunting, wasting) were negatively associated with motor development, emphasizing the importance of adequate nutrition. While some studies reported impaired fitness and motor skills among overweight/obese preschoolers compared to normal-weight peers, others found no differences based on weight status. Relationships between physical activity levels, anthropometrics, and motor outcomes were complex and inconsistent across studies. This review highlights key findings regarding the influence of anthropometric factors on physical capabilities in early childhood. Early identification of children with impaired growth or excessive adiposity may inform tailored interventions to promote optimal motor development and prevent issues like obesity. Creating supportive environments for healthy growth and age-appropriate physical activity opportunities is crucial during this critical developmental window.

Heart rate variability (HRV) is defined as the fluctuation of time intervals between adjacent heartbeats and is commonly used as a surrogate measure of autonomic function. HRV has become an increasingly measured variable by wearable technology for use in fitness and sport applications. However, with its increased use, a gap has arisen between the research and the application of this technology in strength and conditioning. The goal of this narrative literature review is to discuss current evidence and propose preliminary guidelines regarding the application of HRV in strength and conditioning. A literature review was conducted searching for HRV and strength and conditioning, aiming to focus on studies with time-domain measurements. Studies suggest that HRV is a helpful metric to assess training status, adaptability, and recovery after a training program. Although reduced HRV may be a sign of overreaching and/or overtraining syndrome, it may not be a sensitive marker in aerobic-trained athletes and therefore has different utilities for different athletic populations. There is likely utility to HRV-guided programming compared to predefined programming in several types of training. Evidence-based preliminary guidelines for the application of HRV in strength and conditioning are discussed. This is an evolving area of research, and more data are needed to evaluate the best practices for applying HRV in strength and conditioning.

In healthy young adults, electrical stimulation of the superficial peroneal cutaneous nerve (SPn) innervating the dorsum of the foot has been shown to elicit functionally relevant reflexes during walking that are similar to those evoked by mechanical perturbation to the dorsum of the foot during walking and are referred to as stumble corrective (obstacle avoidance) responses. Though age-related differences in reflexes induced by mechanical perturbation have been studied, toe clearance has not been measured. Further, age-related differences in reflexes evoked by electrical stimulation of SPn have yet to be determined. Thus, the purpose of this study was to characterize age-related differences between healthy young adults and older adults with no history of falls in stumble correction responses evoked by electrical stimulation of the SPn at the ankle during walking. Toe clearance relative to the walking surface along with joint displacement and angular velocity at the ankle and knee and EMG of the tibialis anterior, medial gastrocnemius, biceps femoris and vastus lateralis were measured. The combined background and reflex toe clearance was reduced in the older adults compared with the young in mid-early swing (p = 0.011). These age-related differences likely increase fall risk in the older adult cohort. Further, age-related changes were seen in joint kinematics and EMG in older adults compared with the young such as decreased amplitude of the plantarflexion reflex in early swing in older adults (p < 0.05). These altered reflexes reflect the degradation of the stumble corrective response in older adults.

An increase in the delivery and use of oxygen to the musculature in physically active subjects are determinants of improving health-related aerobic capacity. Additional health benefits, such as an increase in the muscle mass and a decrease in fat mass, principally in the legs, could be achieved with weekly global physical activity levels of more than 300 min. The objective was to compare the muscle vascular and metabolic profiles of physically very active and inactive subjects. Twenty healthy men participated in the study; ten were assigned to the physically very active group (25.5 ± 4.2 years; 72.7 ± 8.1 kg; 173.7 ± 7.6 cm) and ten to the physically inactive group (30.0 ± 7.4 years; 74.9 ± 11.8 kg; 173.0 ± 6.4 cm). The level of physical activity was determined by the Global Physical Activity Questionnaire (GPAQ). A resting vascular occlusion test (5 min of an ischemic phase and 3 min of a reperfusion phase) was used, whereas a near-field infrared spectroscopy (NIRS) device was used to evaluate the muscle oxygenation in the right vastus lateralis of the quadriceps muscle. The area under the curve of the deoxyhemoglobin (HHb) during the ischemic phase and above the curve of the tissue saturation index (TSI) during the reperfusion phase were obtained to determine muscle metabolic and vascular responses, respectively. Physically very active group showed a higher absolute HHb (3331.9 ± 995.7 vs. 6182.7 ± 1632.5 mmol/s) and lower TSI (7615.0 ± 1111.9 vs. 5420.0 ± 781.4 %/s) and relative to body weight (46.3 ± 14.6 vs. 84.4 ± 27.1 mmol/s/kg and 106.0 ± 20.6 vs. 73.6 ± 13.8 %/s/kg, respectively), muscle mass (369.9 ± 122.2 vs. 707.5 ± 225.8 mmol/kg and 829.7 ± 163.4 vs. 611.9 ± 154.2 %/s/kg) and fat mass (1760.8 ± 522.9 vs. 2981.0 ± 1239.9 mmol/s/kg and 4160.0 ± 1257.3 vs. ±2638.4 ± 994.3 %/s/kg, respectively) than physically inactive subjects. A negative correlation was observed between HHb levels and TSI (r = -0.6; p < 0.05). Physically very active men (>300 min/week) present better muscle oxidative metabolism and perfusion and perform significantly more physical activity than physically inactive subjects. Extra benefits for vascular health and muscle oxidative metabolism are achieved when a subject becomes physically very active, as recommended by the World Health Organization. In addition, a higher level of physical activity determined by GPAQ is related to better vascular function and oxidative metabolism of the main locomotor musculature, i.e., the quadriceps.

The impact of exercise-specific face masks (ESFMs) in aerobically fit individuals on physiological, perceptual, respiratory, and performance responses remains unclear. How ESFMs mitigate exercise-induced bronchoconstriction (EIB) is also unknown. Thus, this study aimed to determine how an ESFM altered within-exercise physiological, perceptual, respiratory, and performance responses to graded treadmill exercise. Twenty-four individuals (11 females) completed a discontinuous graded exercise test on a treadmill under two conditions (ESFM and unmasked). Physiological, respiratory function, and perceptual measures were assessed. Performance was determined by time to exhaustion. Statistical analyses included linear mixed-effects modeling, repeated measures analysis of variance, and pairwise comparisons using an alpha value of 0.05. ESFM use significantly impaired performance (median = -150.5 s) and decreased arterial oxygen saturation at maximal intensity (mean = -3.7%). Perceptions of air hunger and work of breathing were elevated across submaximal and maximal intensities. Perceived exertion and breathing discomfort were significantly elevated submaximally but not maximally. Spirometry measures were not significantly different at termination but were significantly improved at submaximal intensities in participants with and without EIB. ESFM use in fit individuals increased perceptual discomfort, impaired performance, and augmented arterial desaturation. Respiratory function improvements were observed but were accompanied by adverse perceptual sensations. Despite this, performance impairments may limit the real-world utility of ESFMs for athletes.