Training History-Dependent Functional Role of EMG Model-Predicted Antagonist Moments in Knee Extensor Moment Generation in Healthy Young Adults

Resistance training (RT) improves the skeletal muscle’s ability to generate maximal voluntary force and is accompanied by changes in the activation of the antagonist muscle which is not targeted primarily by RT. However, the nature and role of neural adaptation to RT in the antagonist muscle is paradoxical and not well understood. We compared moments, agonist muscle activation, antagonist activation, agonist-antagonist coactivation, and electromyographic (EMG) model-predicted moments generated by antagonist hamstring muscle coactivation during isokinetic knee extension in leg strength-trained (n = 10) and untrained (n = 11) healthy, younger adults. Trained vs. untrained adults were up to 58% stronger. During knee extension, hamstring activation was 1.6-fold greater in trained vs. untrained adults (p = 0.022). This hamstring activation produced 2.6-fold greater model-predicted antagonist moments during knee extension in the trained (42.7 ± 19.55 Nm) vs. untrained group (16.4 ± 12.18 Nm; p = 0.004), which counteracted (reduced) quadriceps knee extensor moments ~43 Nm (0.54 Nm·kg−1) and by ~16 Nm (0.25 Nm·kg−1) in trained vs. untrained. Antagonist hamstring coactivation correlated with decreases and increases, respectively, in quadriceps moments in trained and untrained. The EMG model-predicted antagonist moments revealed training history-dependent functional roles in knee extensor moment generation.

Static Body Balance in Children and Expert Adults Ballroom Dancers: Insights from Spectral Analysis of Shifts

Objective: The purpose of this study was to assess the differences in maintaining body balance (influence of different sensorial sub-systems) in a representative sample of active Dance Sport competitors (children and adults). Methods: Overall, 13 children and 15 high-level adults sport dancers underwent a static equilibrium test on a force platform, in which 17 different parameters were examined, including a spectral analysis of shifts using an FFT algorithm that can assess the contribution of different somatic-sensory systems on maintaining body balance. Results: Younger subjects rely on their somatic-sensory reactions to maintain their balance, while adults rely more on the vestibular system, according to shifts’ spectral analysis. No differences were noted between the male and female participants. Conclusions: Children predominantly use the somatic-sensory system in body balance, while adults make more use of the vestibular system. According to these results and due to the trainability phases, exercises that challenge the somato-sensorial system are recommended to train balance in young dancers, while exercises that challenge the vestibular system are recommended in adult dancers which who have not developed exceptional somato-sensory balance abilities during their growth and training history.

The effects of uncertain context inference on motor adaptation

Humans have been shown to adapt their movements when a sudden change to the dynamics of the environment is introduced, a phenomenon called motor adaptation. If the change is reverted, the adaptation is also quickly reverted. Human are also able to adapt to multiple changes in dynamics presented separately, and to be able to switch between adapted movements on the fly. Such switching relies on contextual information which is often noisy or misleading, which affects the switch between adaptations. In this work, we introduce a computational model to explain the behavioral phenomena effected by uncertain contextual information. Specifically, we present a hierarchical model for motor adaptation based on exact Bayesian inference. This model explicitly takes into account contextual information and how the dynamics of context inference affect adaptation and action selection. We show how the proposed model provides a unifying explanation for four different experimentally-established phenomena: (i) effects of sensory cues and proprioceptive information on switching between tasks, (ii) the effects of previously-learned adaptations on switching between tasks, (iii) the effects of training history on behavior in new contexts, in addition to (iv) the well-studied savings, de-adaptation and spontaneous recovery.

The Interaction between Dietary Components, Gut Microbiome, and Endurance Performance

Research so far indicates that gut microbiome and diet interactions influence obesity, diabetes, host immunity, and brain function. The ability of athletes to perform to optimum for a more extended time, as well as the ability to resist, withstand, recover from, and have immunity to fatigue, injury depends on the genetic factor, age, sex, training history, psychological factors, mode, intensity and frequency of training and their interactions with the external dietary components. However, recent evidence indicates that the gut microbiome may also potentially influence the development of endurance in response to the type and composition of the external diet, including several food supplements. Thus, the gut microbiome has become another target in the athlete’s pursuit of optimal performance. This chapter discusses the effect of exercise on the gut microbiome, the interplay between dietary components and supplements on the gut microbiome, and its impact on endurance performance.

Alarm warning dan rem otomatis berbasis detak jantung pada olahraga bersepeda

Jantung merupakan organ vital pada tubuh manusia. Oleh karena itu, penting dalam memelihara kesehatan jantung. Salah satunya melalui pelatihan berbasis detak jantung, yaitu menjaga detak jantung dalam kisaran yang ditetapkan. Salah satu pengaplikasiannya adalah olahraga bersepeda, namun tidak jarang pesepeda melebihi target maksimal saat bersepeda, sehingga hal tersebut menyalahi aturan dalam pelatihan. Prinsip kerja alat ini adalah mengaktifkan alarm warning jika detak jantung pengguna melebihi target maksimal saat latihan dan mengaktifkan rem otomatis ketika pengguna menghiraukan alarm warning. Target latihan diperoleh dari perhitungan umur, maximal heart rate (MHR), Rest Heart Rate (RHR), dan riwayat latihan. Penelitian ini menggunakan grove heart rate sensor sebagai sensor detak jantung dengan mikrokontroler Arduino MEGA. Proses pengambilan maupun penyimpanan data pada database dilakukan oleh NodeMCU. Motor DC 12V digunakan sebagai penarik rem dengan driver motor sebagai pengatur arah dan putaran motor. Berdasarkan hasil pengujian diperoleh bahwa data detak jantung peserta latihan tersimpan dalam database sistem, alarm warning bekerja(buzzer on) jika detak jantung peserta diatas 135 bpm, dan rem otomatis bekerja pada saat detak jantung peserta latihan diatas 135 bpm dengan berubahnya panjang tali rem dari 15 cm menjadi 12 cm. The heart is a vital organ in the human body. Therefore, it is important in maintaining heart health. One of them is through heart rate-based training, which is keeping the heart rate within a specified range. One of its applications is cycling, but it is not uncommon for cyclists to exceed the maximum target when cycling, so that this violates the rules in training. The working principle of this tool is to activate an alarm warning if the user's heart rate exceeds the maximum target during training and activate the automatic brake when the user ignores the alarm warning. Training targets are obtained from the calculation of age, maximal heart rate (MHR), Rest Heart Rate (RHR), and training history. This study uses a grove heart rate sensor as a heart rate sensor with an Arduino MEGA microcontroller. The process of retrieving and storing data in the database is carried out by NodeMCU. DC 12V motor is used as a brake puller with the motor driver to control the direction and rotation of the motor. Base on the test result, it is found that the participant’s heart rate data is stored in the database system, the alarm warning work (buzzer on)if the participant’s herat rate is above 135 bpm, and the brakes automatically work when the participant’s herat rate is above 135 bpm by changing the length of the brake rope from 15cm to 12 cm.

Low-dimensional encoding of decisions in parietal cortex reflects long-term training history

Neurons in parietal cortex exhibit task-related activity during decision-making tasks. However, it remains unclear how long-term training to perform different tasks over months or even years shapes neural computations and representations. We examine lateral intraparietal area (LIP) responses during a visual motion delayed-match-to-category (DMC) task. We consider two pairs of monkeys with different training histories: one trained only on the DMC task, and another first trained to perform fine motion-direction discrimination. We introduce generalized multilinear models to quantify low-dimensional, task-relevant components in population activity. During the DMC task, we found stronger cosine-like motion-direction tuning in the pretrained monkeys than in the DMC-only monkeys, and that the pretrained monkeys' performance depended more heavily on sample-test stimulus similarity. These results suggest that sensory representations in LIP depend on the sequence of tasks that the animals have learned, underscoring the importance of training history in studies with complex behavioral tasks.

Does the Multistage 20-m Shuttle Run Test Accurately Predict VO2max in NCAA Division I Women Collegiate Field Hockey Athletes?

Laboratory assessments of maximal oxygen uptake (VO2max) are considered the “gold standard” for ascertaining cardiovascular fitness, but they are not always practical for use in team sport settings. Therefore, the purpose of the current study was to compare the criterion assessment of VO2max on a treadmill to the progressive, multistage 20-m shuttle run test (i.e., Beep test), and to determine the predictability of 6 previously established Beep test predictive equations (i.e., Chatterjee, Flouris, Leger, Leger and Gadoury, Ramsbottom, St. Clair-Gibson). Collegiate women field hockey athletes (n = 65, mean±SD: age 19.6 ± 1.2 years; weight 64.7 ± 6.1 kg) completed criterion VO2max (mean ± SD: 46.4 ± 4.6 mL·kg−1·min−1) and Beep tests to volitional fatigue. According to Bland–Altman and Ordinary Least Products Regressions, the Ramsbottom (46.5 ± 4.2 mL·kg−1·min−1) and Flouris (46.3 ± 3.8 mL·kg−1·min−1) equations were considered valid predictions of criterion measured VO2max (46.4 ± 4.6). The Chatterjee, Leger, Leger and Gadoury, and St. Clair-Gibson equations overestimated VO2max, and are not recommended for use with women collegiate field hockey athletes. The Ramsbottom and Flouris estimates of VO2max from 20-m shuttle performances may be used in this population. For accurate estimates of VO2max, the clientele’s age, fitness level, and training history should be considered when selecting equations.

Oxygen Uptake Kinetics in Endurance Trained Youth and Adult Cyclists

Previous studies reported faster pulmonary oxygen uptake kinetics at the onset of exercise in untrained youth compared with adults. Whether or not these differences are identical for trained groups have not been examined. The purpose of this study was to compare ̇VO2 kinetics of youth and adult cyclists at moderate and heavy-intensity exercise. Thirteen adult (age: 23.2 ± 4.8 years; ̇VO2peak 68.4 ± 6.8 mL·min-1.kg-1) and thirteen youth cyclists (age: 14.3 ± 1.5 years; ̇VO2peak 61.7 ± 4.3 mL·min-1.kg-1) completed a series of 6-min square wave exercises at moderate and heavy-intensity exercise at 90 rev·min-1. A two-way repeated-measure ANOVA was conducted to identify differences between groups and intensities. The time constant, time delay and the mean response time were not significantly different between youth and adult cyclists (p > 0.05). We found significant differences between intensities, with a faster time constant during moderate than heavy-intensity exercise in youth (24.1 ± 7.0 s vs. 31.8 ± 5.6 s; p = 0.004) and adults (22.7 ± 5.6 s vs. 28.6 ± 5.7 s; p < 0.001). The present data suggest that the effect of training history in adult cyclists compensate for the superior primary response of the oxygen uptake kinetics typically seen in youth compared to adults. Furthermore, the ̇VO2 response is dependent of work rate intensity in trained youth and adult cyclists.