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Effects of Detraining onthe Training-InducedBalanceAbilityin Humans

Han-Nien Huang1, Takashi Yamamoto2

1Center of Physical Education, Ming Chuan University, Taoyuan,Taiwan, 2Graduate School of Health and Sport Sciences,Chukyo University,Toyota,Japan

ABSTRACT

Huang HN, Yamamoto T. Effects ofDetraining on the Training-Induced Balance Abilityin Humans. JEPonline2014;17(1):50-57. In our previous study of balance training, we found that more than 2 dwk-1balance training frequency for 8 wks with 10 consecutive trials augmentedbalance ability in healthy young adults. However, it is unclear whether this training-induced balance ability is maintained or not for a long duration after the cessation of balance training (detraining). The purpose of this study was to investigate the effects of detraining on the training-induced balance abilityin humans.The values of training-induced effects at just post-training in our previous study were used as starting point of detraining.Thirty-five male students (mean age,21.2± 0.6 yrs)were divided into 4 groups: (a)non-training (control) group (n=9); (b) 1 d·wk-1 training (W1; n=9); (c)2 d·wk-1 training (W2; n=10); and (d) 3 d·wk-1 training (W3; n=7).The subject standing on an unstable seesaw-like platform was required to maintain balance as long as possible at each trial, and then the balance keeping time (BKT) was recorded together with the changes in the angle of an inclining platform and head movement acceleration of the subject’s forehead.The training period was 8 wks, which was followed by a 21-wk detraining period.The findings indicate that the significant training-induced balance ability (ΔBKTs) in W2 and W3 groups at post-training was maintained for at least 21 wks even after the termination oftraining.We also found no significant change in the magnitude of angular velocity of platform rotation during detraining. However, training-induced effects for head movements disappeared during detraining.

Key Words: Dynamic Balance,Detraining,Postural Control

INTRODUCTION

As emphasized in our previous study (7), the ability to keep balance on an unstable support surface is extremely important inmany sports events such assurfboarding,skiing, figure skating, gymnasticsandour daily life as whenstanding in moving trains.Especially in the older adult populations, balance ability has also been regarded as an important indicator for musculoskeletal health. As a result, numerous researchers have designed and tested their training programs and investigated the training effects on balance performance (1,9,10,11). They have also discussed the improvements in static and dynamic balance ability in regards to athletics and health.

Very few studies to our knowledge have examined the detraining effects on the subjects’ balance performance. To some degree, Toulotte et al. (9) demonstrated that the training effects returned to the initial state after a 3-month detraining period. It is very interesting whether the balance ability decreases or notduring more prolonged detraining.

Hence, thepurpose of this study was to study theeffects of detraining of ~5 months on the training-induced balance ability while recording the changes in the seesaw-likeplatformmovements and head acceleration to better understand the subjects’ underlying postural control.The findings should be helpful for both interpreting postural control and developing balance ability.

METHODS

Subjects

All the subjects who participated in the present study were healthy male undergraduate studentsat the School of Health and Sport Sciences of Chukyo University in Japan. They were free from any balancing disorders. Their age ranged from 20 to 22 yrs. Height, body weight, and BMI were 162.4 to 184.7 cm, 55.0 to 80.5 kg, and 19.6 to 26.2 kg·m-2, respectively.To investigate the effects of detraining on the subjects’ training-induced balance ability, we used a Control Group (n = 9) and 3 Training Groups, which were divided into subgroups: W1 (n = 9), W2 (n = 10), and W3 (n = 7) that consisted of the number of training day(s) per week. Initially, the number of subjects in each group was 10 but, during the course of the study, 5 subjects were unable to carry out the balancing task because of their injuries in physical education classes (2 subjects) or scheduling problems (3 subjects). Their data were eliminated from the statistical analysis. Thirty-five subjects completedthe study. There were no significant differences among the 4 groups except in the age of the subjects.The experimental protocol was approved by the Ethics Committee at Chukyo University Graduate School of Health and Sport Sciencesin Japan, and also the experiments were conducted in accordance with the Declaration of Helsinki. After the subjects were informed of the experimental advantages and possible risks, they signed their written consent forms prior to participation in this study.

Measurement of Balance Performance

For measuring balance performance, a custom-built seesaw-like platform was used as reported in the previous study (7) on which the subject was instructed to stand barefoot and to do his best to maintain the standing posture as long as possible. This platform is capable of rotating around the pitch-axis in both directions of toes-up and toe-down, and its maximum inclination was set at an angleof 25° to the horizontal plane, which was confirmed to be sufficient to cause imbalance in all subjects. An electrogoniometer was installed on the tip of the horizontal pivotto record the changes in platform movementduring balancing.Each subject was instructed to look at a fixed eye-level cross mark at a distance of approximately 3 m. Testing consisted of one session of 10 successive trials of balancing per day of which the mean time of each subject’s balance keeping time (BKT) was calculated and adopted as his balance ability.

Balance Detraining Programs

In order to investigate the effects of detraining on the training-induced balance ability, training and detraining programs were set. Before training, each subject’s BKT was measured as baseline level. Then, the subjects were randomly divided into 3 training groups that participated in the prescribed training programs of either1 d·wk-1 of training (W1), 2d·wk-1 of training (W2), or 3d·wk-1 of training. A 1-day training session consisted of 10 successive trials of balancing. Each subject took an appropriate rest among trials for preventing fatigue. The training period was 8 wks in all groups, and the BKT was recorded on all trials. The training program was immediately followed by detraining during which the BKT was again measured at week 9 and 21. Thetotal duration of the study was 31 wks (~7 months).

Signal Recording and Analyzing system

All the signals, such as angular changes in the platform position, the angular velocity of the platform obtained by the derivative that provides offline calculation of first order derivatives of platform movement, the output from the accelerometer (BAH-10G, Shinko, Japan) attached to the forehead of the subject, the start and stop signals from the button operated by the subject and from the platform contact switch,were collected simultaneously into the Universal Data Recorder (Model A-69, Sony Magnescale, Japan) as a backup device through amplifiers (Model NS901, San-ei, Japan) without working any filters. The signals were then led to the data acquisition system (PowerLab 8/30, ADInstruments Japan Inc.) for signal recording and for further processing and analysis (PowerLab Chart ver.5 software package) in combination with a personal computer (IBM, Taiwan). Root mean squares (RMS) were calculated for both the angular velocity of the platform and acceleration of the head movement, and adopted as indices of platform and head movements, respectively. All the signals were recorded at a sampling frequency of 100 Hz.

Statistical Analyses

All the values were expressed as means±standard deviations (SD) unless stated otherwise. Statistical analyses consisted of using both the statistical software packages SPSS version 11.0 for Windows XP (SPSS Inc., Japan) and the statistical analysis add-in software (Statcel 2, SSRI Inc., Japan) for Excel 2002. After confirming normality of distribution (via the Shapiro-Wilk’s test) and equality of variance (using the Levene’s test),the data were analyzedusing a one-way analysis of variance (ANOVA). Significant differences among groups in each phase or among the 3 phases within each group were then determined using Tukey’s post-hoc test including Tukey-Kramer one.The level of statistical significance was set at P0.05, while P-values ≤0.1 were reported to indicate trends.

RESULTS

Detraining Effects on Balance Performance

The absolute changes in BKT (ΔBKT) of each group after training and detraining are shown in Figure 1. At the 9th-wk after the termination of training (DT9-W), the ΔBKT of the W2 Group was significantly larger than those of W1 and the Control (P0.05, P0.01, respectively). Also, the ΔBKT of the W3 Group was significantly larger than that of the Control Group (P0.05), but it was not significantly larger than that of W1 Group (P = 0.117). However, there were no significant differences between the W1 Group and the Control Group, as well as between W2 and W3 Groups. At week 21 after the termination of training (DT21-W), the ΔBKT of the W2 Group was significantly larger than the W1 Group and the Control Group (P0.05 for both). Also, the ΔBKT of the W3 Group was significantly larger than that of the W1 Group and the Control Group (P0.05 for both). However, there were no significant differences between the W1 Group and the Control Group, as well as between W2 and W3 Groups.

Figure1. Comparisons of ∆BKTs in 4Groups (Control,W1,W2,and W3) Immediately After 8 wks of Training (post-training), After 9 wks (Detraining 9-W) and 21 wks (Detraining 21-W) of Detraining. Values are means ± SD.

* and ** : significantly different at P0.05 and P0.01, respectively.

Figure2. Comparisons of ΔBKT Among Post-training (Post) and Detraining (DT9-W, DT21-W) Phases Within Each Group. Values are means ± SD. n.s.: No significant difference among three phases.

In order to show the detraining effects more clearly,the ΔBKT was re-arranged across the 3 testing phases within each group (Figure 2). As shown, there were no significant changes in ΔBKT across the 3 testing phases within each Group. Therefore, the positive effects of training in the W2 and the W3 Groups obtained during the training phase were not decreased even at week 9 and 21 (DT9-W and DT21-W, respectively) after the termination of balance training.

Changes in Platform Movement and Head Acceleration during Detraining

Figures3A and 3B show the changes in ΔRMS angular velocity of the platform movement (Panel A) and ΔRMS head acceleration (Panel B) during balance training and detraining. Although no significant difference was found in Figure3A, ΔRMS angular velocity in the W2 Group had a tendency to decrease compared to the W1 Group after training (P = 0.100) and the Control Group at week 21 after the termination of training (DT21-W) (P = 0.082).

On the other hand, as shown in Figure3B, ΔRMS head acceleration in the W1, W2, and W3 Groups was significantly larger than that of the Control Group after training (P0.01, P0.001, P0.01, respectively). However, no significant differences in ΔRMS head acceleration were found among the four Groups during detraining (DT9-W and DT21-W).

Figure3. Comparisons of ΔRMS Angular Velocity (A.V.) (Panel A) and ΔRMS Head Acceleration (H.A.) (Panel B) in 4Groups (Control,W1, W2, and W3) Immediately After 8 wks of Training (Post-training), After 9 wks (DT 9-W) and 21 wks (DT21-W) of Detraining. Values are means ± SD.#A trend (P = 0.100) of a more decrease in ΔRMS angular velocity (A.V.) in the W2 Group than in the W1 Group. †A trend (P= 0.082) of a more decrease in ΔRMS angular velocity (A.V.) in the W2 Group than in the Control Group.** and *** significantly different at P0.01 and P0.001, respectively.

Figures4A and 4Bshow the changes in ΔRMS angular velocity (Panel A) and ΔRMS acceleration of the head movements (Panel B) across 3 different testing phases within each Group. As shown in Figure4A, no significant changes in ΔRMS angular velocity of the platform were found within the Groups. On the other hand, as shown in Figure4B, the training-induced increments of the ΔRMS head acceleration in all training Groups diminished during detraining (DT9-W and DT21-W).

Figure4. Changes in ΔRMS Angular Velocity (Panel A) and ΔRMS Head Acceleration (Panel B) at Different Phases (Post (post-training), DT9-W, DT21-W) Within Each Group. Values are means ± SD.No significant intra-group differences in ΔRMS angular velocity (A.V.) were found among 3 phases.** and *** significantly different at P0.01 and P0.001, respectively.

DISCUSSION

Detraining Effects on Balance Performance

The most interesting finding is that the balance training effects did not decrease at week 21 after the cessation of training (at DT21-W), which adds to the relatively few studies on the detraining effects on balance performance. Fatouros et al. (3) examined the relationship between training intensity and training effects on mobility (time up and go, walking, climbing stairs) in older men and found that training effects on mobility in response to high intensity training lasted for a long time. It is true in general that muscle strength training effects are decreased considerably after the termination of training in young adults (5).

The extent to which the detraining-induced decrease in muscular performance in middle-aged and elderly subjectsis related to the duration of detraining is discussed by Häkkinen et al. (4) who reported that short-term detraining of 3 wks caused minor changes in muscular performances, while prolonged detraining of 24 wks decreased maximal strength and cross-sectional area of the rectus femoris muscle. Although a certain limitation on direct comparison between the study by Häkkinen et al. (4) and the present studyshould be recognized, balance training effects were still maintained after the prolonged detraining of 21 wks while the 24-wk detraining period resulted in a significant decrease in muscle strength. The fact that the training effects on balance performance are maintained for a long period in the present study is an important finding from the muscle strength training effects.

The prolonged maintenance of balance training effects after the termination of balance training suggests the establishment of a new adaptive control system. It also supports the concept proposed by Ito (10) concerning the new formation of neural networks in the cerebellar cortex accompanying the acquisition of motor skills by repeating voluntary movements. Furthermore, the data may suggest the existence of a morphological selective increase in the trained part of the brain that has a favorable effect on maintenance after detraining that is similar to the work of Boyke et al. (2).

Changes in the Platform Movement and Head Movement Accelerationdue to Detraining

The present study demonstrated that the increment of head acceleration in training groups at post-training diminished at 9-wks and 21-wks of detraining, while the decrement of ankle joint movement in the W2 group was maintained during the prolonged detraining period (P= 0.082). These results are partly consistent with the findings of Horak and Nashner (8) who demonstrated, first, the occurrence of progressive changes in the relative amplitude and timing of two joints strategy components and, second, the influence of the subjects’ recent experiences on the combination of the strategies.

One possible speculation about the postural control observed in the present study is that atthe 21st-wk of detraining in the W2 group, the balancing posture was maintained with less ankle joint angular rotation and without more head moving, which partly relates to the hypothesis concerning training-dependent changes in postural control. This suggests the progressive changes in the combination of postural control strategies and the development of balance ability. Then, too, since there were fewer movements in both the platform and the subjects’ head after prolonged detraining, some passage of time may be necessary for working of further developed postural control system that adapts to maintain balance. However, it must be noted that this tendency was limited in the W2 training group.

CONCLUSIONS

This study found that the training-induced increases in balance performance as training effects were maintained after the detraining period of 21 wks. There was no significant change in the magnitude of angular velocity of platform movements during detraining. However, we found the returning to the baseline level in head acceleration in all training groups. These data may suggest the progressive changes in the combination of postural control strategies underlying the development of balance ability.

ACKNOWLEDGMENTS

The authors are grateful to both the undergraduatestudentsand Research Institute of Health and Sport Sciences affiliated with ChukyoUniversityin Japanfor their participation and support.

Address for correspondence: HN Huang, MA, Center of Physical Education, Ming Chuan University, De Ming Rd. Sec. 5, Guishan District, Taoyuan 333,Taiwan, Phone: +886 3 3507001 # 5340, Fax: +886 3 3593862; Email:

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