changes in that test. 13 Using the CV%, the sensitivity of a test can be established via signal to noise ratio (SNR) analysis. 12 Indeed, measurement signal is often assessed via intervention studies where responsiveness (ie, a change in performance) is measured following the intervention 14 ; however
Samuel Ryan, Emidio Pacecca, Jye Tebble, Joel Hocking, Thomas Kempton and Aaron J. Coutts
Joseph Hamill, Graham E. Caldwell and Timothy R. Derrick
Researchers must be cognizant of the frequency content of analog signals that they are collecting. Knowing the frequency content allows the researcher to determine the minimum sampling frequency of the data (Nyquist critical frequency), ensuring that the digital data will have all of the frequency characteristics of the original signal. The Nyquist critical frequency is 2 times greater than the highest frequency in the signal. When sampled at a rate above the Nyquist, the digital data will contain all of the frequency characteristics of the original signal but may not present a correct time-series representation of the signal. In this paper, an algorithm known as Shannon's Sampling Theorem is presented that correctly reconstructs the time-series profile of any signal sampled above the Nyquist critical frequency. This method is superior to polynomial or spline interpolation techniques in that it can reconstruct peak values found in the original signal but missing from the sampled data time-series.
Valentina Agostini, Emma Chiaramello and Marco Knaflitz
Static posturography provides an objective assessment of postural control by characterizing the body sway during upright standing. The center of pressure (COP) signal is recorded by a force platform, and it is analyzed by means of many different models and techniques. Most of the parameters calculated according to these different approaches are affected by relevant intra- and intersubject variability or do not have a clear physiological interpretation. Traditional approaches decompose the COP signal into anteroposterior and mediolateral time series, corresponding to ankle plantar/dorsiflexion and hip adduction/abduction, respectively. In this study we hypothesized that COP signals show inherent rotational characteristics. To verify our hypothesis we applied the rotary spectra analysis to the two-dimensional COP signal to decompose it into clockwise and counterclockwise rotational components. We demonstrated the presence of rotational components in the COP signal of healthy subjects, providing a reference data set of the spectral characteristics of these components.
Jeffrey N. Howard
The game of baseball and its internal cryptic communication system has always been vulnerable to sign stealing. By systematically studying the signals of an opponent so as to decrypt and intercept opponent communications, one can garner valuable insight into future events and strategies. Such “theft of signals” can lead teams to frequently change their sign indicator, should they suspect it has been compromised. The current paper presents a theoretical process of “hot” sign indicator obfuscation whereby the pitcher and catcher use unique hot indicator values that are generated after each pitch via an algorithm derived from randomly changing situational and/or scoreboard data.
Panagiota Klentrou, Kirina Angrish, Nafisa Awadia, Nigel Kurgan, Rozalia Kouvelioti and Bareket Falk
measured in the blood are a product of osteocytes, thus they directly reflect osteocyte activity ( 41 ), which is not the case for other osteokines. Sclerostin is a catabolic osteokine that decreases bone formation via the inhibition of Wnt signaling ( 21 ). It binds to low-density lipoprotein receptor
Francisco Javier Alonso, Publio Pintado and José María Del Castillo
The use of the Hodrick-Prescott (HP) filter is presented as an alternative to the traditional digital filtering and spline smoothing methods currently used in biomechanics. In econometrics, HP filtering is a standard tool used to decompose a macroeconomic time series into a nonstationary trend component and a stationary residual component. The use of the HP filter in the present work is based on reasonable assumptions about the jerk and noise components of the raw displacement signal. Its applicability was tested on 4 kinematic signals with different characteristics. Two are well known signals taken from the literature on biomechanical signal filtering, and the other two were acquired with our own motion capture system. The criterion for the selection of cutoff frequency was based on the power spectral density of the raw displacement signals. The results showed the technique to be well suited to filtering biomechanical displacement signals in order to obtain accurate higher derivatives in a simple and systematic way. Namely, the HP filter and the generalized cross-validated quintic spline (GCVSPL) produce similar RMS errors on the first (0.1063 vs. 0.1024 m/s2) and second (23.76 vs. 23.24 rad/s2) signals. The HP filter performs slightly better than GCVSPL on the third (0.209 vs. 0.236 m/s2) and fourth (1.596 vs. 2.315 m/s2) signals.
Ricardo Pires, Thays Falcari, Alexandre B. Campo, Bárbara C. Pulcineli, Joseph Hamill and Ulysses Fernandes Ervilha
muscle activation differs according to the rate of application of the impact forces as well as the interaction between the foot and the ground. 5 It is not clear whether the electromyographic (EMG) signal differences obtained when comparing shod and barefoot running are solely related to the way the
Jennifer Dekker, Katlynne Nelson, Nigel Kurgan, Bareket Falk, Andrea Josse and Panagiota Klentrou
The canonical Wnt signaling pathway is a key regulator of bone metabolism. Uninhibited Wnt signaling allows for bone anabolism ( 17 ) and determines the fate and survival of bone cells ( 41 ). Specifically, Wnt signaling allows for gene transcription to occur within the osteocyte in favor of bone
Resistance exercise can effectively result in an increase in muscle mass, or hypertrophy, which generally becomes apparent after several weeks of training. Muscle hypertrophy requires muscle protein synthesis to exceed protein breakdown during an extended time period. It has been firmly established that the interaction between exercise and nutrition (i.e., protein intake) is necessary to attain net protein accretion in skeletal muscle. The stimulation of protein synthesis is caused in part by stimulation of mRNA translation initiation. There is relatively little information on the response of intracellular signaling controlling mRNA translation to exercise and nutrition, especially in humans, but the available data in humans seem to suggest that a single bout of resistance exercise does not substantially enhance PI-3 kinase/mTOR signaling during the first 2 h after exercise. Moreover, it is demonstrated that the ingestion of protein or amino acids after exercise is crucial to further stimulate molecular signaling that controls translation initiation. The aim of this review is to provide an overview of the intracellular signaling related to translational control and to provide a summary of the current knowledge about the response of the signaling pathways controlling the anabolic response to exercise and nutrient intake in vivo in humans.
Thomas W. Jones, Ian H. Walshe, David L. Hamilton, Glyn Howatson, Mark Russell, Oliver J. Price, Alan St Clair Gibson and Duncan N. French
To compare anabolic signaling responses to differing sequences of concurrent strength and endurance training in a fed state.
Eighteen resistance-trained men were randomly assigned to the following experimental conditions: strength training (ST), strength followed by endurance training (ST-END), or endurance followed by strength training (END-ST). Muscle tissue samples were taken from the vastus lateralis before each exercise protocol, on cessation of exercise, and 1 h after cessation of strength training. Tissue was analyzed for total and phosphorylated (p-) signaling proteins linked to the mTOR and AMPK networks.
Strength-training performance was similar between ST, ST-END, and END-ST. p-S6k1 was elevated from baseline 1 h posttraining in ST and ST-END (both P < .05). p-4E-BP1 was significantly lower than baseline post-ST (P = .01), whereas at 1 h postexercise in the ST-END condition p-4E-BP1 was significantly greater than postexercise (P = .04). p-ACC was elevated from baseline both postexercise and 1 h postexercise (both P < .05) in the END-ST condition. AMPK, mTOR, p38, PKB, and eEF2 responded similarly to ST, ST-END, and END-ST. Signaling responses to ST, ST-END, and END were largely similar. As such it cannot be ascertained which sequence of concurrent strength and endurance training is most favorable in promoting anabolic signaling.
In the case of the current study an acute bout of concurrent training of differing sequences elicited similar responses of the AMPK and mTOR networks.