Psychophysical Effects of Music on Gait of School Children

Effect of Synchronous Beats on Human Gait during Unilateral Shoulder Load Carriage

Swetambri*1, Sonal Atreya2, Sneh Anand2

Faculty of Sciences,Jamia Hamdard, New Delhi Centre for Biomedical Engineering, Indian institute of Technology, Delhi

ABSTRACT Carrying heavy loads is known to cause a change in the gait. This study examines the gait pattern in subjects carrying backpack of 12% of their body weight while walking on a force platform. Relationship between gait and synchronous beats was explored by conducting experiments where the subjects walked to synchronized beats while carrying load. The purpose of the study was to determine the impact of auditory rhythm in reducing the effect of load on gait parameters (stride length) and eventually making them symmetric.

1. INTRODUCTION Human gait is the way locomotion is achieved using human limbs. Walking is the most common human gait. It is characterized by alternating steps of left and right lower limbs. The gait cycle is used to describe the complex activity of walking, or our gait pattern. Music and Rhythm have been extensively and universally utilized to accompany motor activity [1]. The interaction between auditory rhythm and physical response has been effectively harnessed for specific therapeutic purposes like to cure stroke patients [2, 3] and for patients with Parkinson’s disease (PD) [4]. There is a close relationship between music and body movement as listening to music is often accompanied by body movements. Soldiers walk on the beat of military marches, bricklayers and people performing physical and often repetitive tasks sing work songs to synchronize their physical movements [5]. Music has the capacity to capture attention, lift spirits, generate emotion, change or regulate mood, evoke memories and encourage rhythmic movement. Also in music theory it has been observed that the moderate musical tempi are close to some biological rhythms of the human body such as the heartbeat and the tempo of walking [6]

The increased mass of loaded backpack makes it harder to initiate motion and requires greater moments about the axes of rotation to control motion. Load carriage has the potential to alter postural control mechanisms which may in turn alter the risks of falls and injury. Many adult populations either wear a heavy external load such as a backpack or carry extra weight. Studies have shown changes in gait as a consequence of wearing a heavy backpack in adults. A strong association was found between habitual heavy backpack carriage and spinal symptoms such as fatigue, muscle soreness, back pain, numbness, shoulder pain and even spinal deformity [7, 8, 9, 10].

Along with these physical problems a change in the gait is a possibility. This will be especially higher in cases where people wear their backpack on a single shoulder. With load subjected on one shoulder there is a tilt in the pelvic due to which the gait becomes asymmetric. The relationship between gait parameters and various synchronous beats is explored to relate the tempi of the stimuli to distance gait parameters (eg.stride length). In this experiment we studied whether auditory rhythm could reduce the effect of load so that the stride length corresponded with that during unloaded condition. 2. METHODOLOGY

2.1 Participants Participants were in the age group of 20-25 years. All subjects were diagnosed for any musculoskeletal problems at the time of testing. A consent form was signed before the trial and body weight and height was recorded. Subjects were given ample time to familiarize themselves with the purpose of the study and the equipment used.

2.1.1 In this study a commercially available athletic bag was used. Each subject was assigned to carry a load of 12% of their body weight on a single shoulder. With every subject, bag was weighed up to 12% of their body weight as shown in Figure1.

Fig.1 weighing of bag up to 12% of the body weight of the subject

It was made sure that the back pack was properly adjusted on the back and the straps fit comfortably on the shoulders and arms and did not cause any discomfort to the subject. The shoulder straps were adjusted and checked using a tape measure before each trial, with the ‘tight’ straps condition defined as a distance of 7cm from the tip of the shoulder strap adjustment buckle to the lower connection of the shoulder strap to the backpack [11].

2.1.2 There were five trials; normal walk (unloaded), walk with backpack on single shoulder, and then with bag, subjects were made to listen to ascending auditory beats; slow beats (60beats/min), medium beats (100 beats /min), fast beats (120 beats/min). First, subjects were asked to walk at their comfortable speed on the force platform. Between every trial, subjects were given a rest of 5 min to regain stable conditions. Subjects walked while listening to three different pieces of musical composition.

2.1.3 People prefer music with tempi ranging from 70 to 100 cycles per minute similar to that of adults' heart rate within normal daily situations [12]. Therefore we selected ascending beats from 60-120 beats /min. The musical pieces consisted of continuous beats at regular intervals .Each piece was 30 sec long. Participants started walking as soon as they heard the first musical beat. Subjects were instructed to walk at their normal comfortable pace but they were free to vary their speed or cadence if they feel like doing so. Beats were recorded using synthesizer/sequencer. Music was played with an mp3 player and subjects wore headphones. The headphones also helped minimize the external noise. At the beginning of each session the experiment instructor activated the mp3 player and mp3 recorder. The amplitude of all musical fragments was normalized. 2.2 Measurement Gait analysis was obtained by means of zebris FDM System. It consists of high quality capacitive force sensors arranged in matrix. Measuring plate analyzes static and dynamic force distribution underfoot while standing and walking. The measuring plate is 1.5metres in length and is integrated in a level walking area. The measuring parameters are automatically calculated in the software program (winFDM software). The main gait parameters are shown in the Evaluation report. These include the stride length, step width, stance, swing, and double support phase and also the cadence. The system is connected directly to a commercially available PC via a USB interface and requires no additional electronics. All the data would be acquired at the 100Hz sampling frequency. The data in this study was obtained from the mean values of 3-4 consistent cycles of walking over the force platform. Data processing and analysis were performed on MATLAB (The Math Works Inc, US).

2.3 Statistical analysis Correlation coefficients were calculated with MATLAB to determine the relationship between gait parameters (stride length) during normal walk and with ascending synchronous beats. The Pearson product-moment correlation was used to find correlation. Karl Pearson coefficient of correlation is given by the following equation.

Where, r is the correlation coefficient, n is the no. of samples (8), x is the normal stride length of each subject and y is the stride length of each subject while listening to auditory beats

3. RESULTS

Gait analysis The data revealed that subject’s walking pattern improved with the advent of auditory rhythm and stride length obtained correlated with that obtained in unloaded condition. Furthermore, highest positive correlation was found with 100 beats/ min as compared to other tempi. The correlation coefficients between stride length during normal walk and auditory beats are summarized in Table 1.There was a correlation between stride length during normal walk and beats at 60 and 100 beats/min (P<0.05). No significant correlation was found with 120 beats /min.

Types of Synchronous Beats 60 beats/min 0.7357* 100 beats/min 0.7651* 120 beats/min 0.1610 *P<0.05

Table1- Correlation coefficients between stride length during normal walk and auditory beats

The three scatter diagrams show correlation between normal walk and 60 beats/min (Fig.1), between normal walk and 100 beats /min (Fig.2), and between normal walk and 120 beats/min (Fig.3) 1 4 0 r = 0 . 7 3 5 7 1 3 5

1 3 0 n i 1 2 5 m / s t a

e 1 2 0 b 0 6 )

m 1 1 5 c ( h t g

n 1 1 0 e l

r 1 0 5 t s 1 0 0

9 0 8 0 8 5 9 0 9 5 1 0 0 1 0 5 1 1 0 1 1 5 1 2 0 1 2 5 s t r i d e l e n g t h ( c m ) n o r m a l Fig.1 Correlation between normal walk and 60 beats /min

r = 0 . 7 6 5 1 1 4 0 n i 1 3 0 m / s t a e b

0 1 2 0 0 1 ) m c ( h

t 1 1 0 g n e l

r 1 0 0 t s

8 0 8 0 8 5 9 0 9 5 1 0 0 1 0 5 1 1 0 1 1 5 1 2 0 1 2 5 s t r i d e l e n g t h ( c m ) n o r m a l Fig.2 Correlation between normal walk and 100 beats /min

1 4 0 r = 0 . 1 6 1 0 1 3 0 n i

m 1 2 0 / s t a e b

0 1 1 0 2 1 ) m c (

h 1 0 0 t g n e l

e d i 9 0 r t s

7 0 8 0 8 5 9 0 9 5 1 0 0 1 0 5 1 1 0 1 1 5 1 2 0 1 2 5 s t r i d e l e n g t h ( c m ) n o r m a l Fig.3 Correlation between normal walk and 120 beats /min 4. DISCUSSION The results of this study show that rhythmic auditory beats have pronounced effect and there is a statistically significant relationship between stride length during normal walk and synchronous beats in the presence of load. This proves that effect of load carriage on gait parameters has reduced in the presence of synchronous beats and stride length improved coming closer to normal stride length. This experiment suggests that auditory rhythm has a comprehensive spatial effect on improvement of total gait pattern (stride length) and surpasses the effect of load carriage.

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