Whenever a voice disorder is present, a change in the normal functioning of the physiology responsible for voice production may be assumed. These physiological events are measurable and may be modified by voice therapy. Normal voice production depends on a relative balance among airflow, supplied by the respiratory system; laryngeal muscle strength, balance, coordination, and stamina; and coordination among these and the supraglottic resonators (pharynx, oral cavity, nasal cavity). Any disturbance in the relative physiological balance of these vocal subsystems may lead to or be perceived as a voice disorder. Disturbances may occur in respiratory volume, power, pressure, and flow, and may manifest in vocal fold tone, mass, stiffness, flexibility, and approximation. Finally, the coupling of the supraglottic resonators and the placement of the laryngeal tone may cause or be implicated in a voice disorder (Titze, 1994).

The overall causes of vocal disturbances may be mechanical, neurological, or psychological. Whatever the cause, one management approach is direct modification of the inappropriate physiological activity through direct exercise and manipulation. When all three subsystems of voice are addressed in one exercise, this is considered holistic voice therapy. Examples of holistic voice therapy include Vocal Function Exercises (Stemple, Glaze, and Klaben, 2000), Resonant Voice Therapy (Verdolini, 2000), the Accent Method of voice therapy (Kotby, 1995; Harris, 2000), and the Lee Silverman Voice Treatment (Ramig, 2000). The following discussion considers the use of Vocal Function Exercises to strengthen and balance the vocal mechanism.

The Vocal Function Exercise program is based on an assumption that has not been proved empirically. Nonetheless, this assumption and the clinical logic that follows have been supported through many years of clinical experience and observation, as well as several efficacy studies (Stemple, 1994; Sabol, Lee, and Stemple, 1995; Roy et al., 2001). In a double-blind, placebo-controlled study, Stemple et al. (1994) demonstrated that Vocal Function Exercises were effective in enhancing voice production in young women without vocal pathology. The primary physiological effects were reflected in increased phonation volumes at all pitch levels, decreased airflow rates, and a subsequent increase in maximum phonation times. Frequency ranges were extended significantly in the downward direction.

Sabol, Lee, and Stemple (1995), experimenting with the value of Vocal Function Exercises in the practice regimen of singers, used graduate students of opera as subjects. Significant improvements in the physiologic measurements of voice production were achieved, including increased airflow volume, decreased airflow rates, and increased maximum phonation time, even in this group of superior voice users.

Roy et al. (2001) studied the efficacy of Vocal Function Exercises in a population with voice pathology. Teachers who reported experiencing voice disorders were randomly assigned to three groups: Vocal Function Exercises, vocal hygiene, and control groups. For 6 weeks the experimental groups followed their respective therapy programs and were monitored by speech-language pathologists trained by the experimenters in the two approaches. Pre_-and post-testing of all three groups using the Voice Handicap Index (VHI; Jacobson et al., 1997) revealed significant improvement in the Vocal Function Exercise group, and no improvement in the vocal hygiene group. Subjects in the control group rated themselves worse.

The laryngeal mechanism is similar to other muscle systems and may become strained and imbalanced for a variety of reasons (Saxon and Schneider, 1995). Indeed, the analogy that we often draw with patients is a comparison of knee rehabilitation with rehabilitation of the voice. Both the knee and the larynx consist of muscle, cartilage, and connective tissue. When the knee is injured, rehabilitation includes a short period of immobilization to reduce the effects of the acute injury. The immobilization is followed by assisted ambulation, and then the primary rehabilitation begins, in the form of systematic exercise. This exercise is designed to strengthen and balance all of the supportive knee muscles for the purpose of returning the knee as close to its normal functioning as possible.

Rehabilitation of the voice may also involve a short period of voice rest after acute injury or surgery to permit healing of the mucosa to occur. The patient may then begin conservative voice use and follow through with all of the management approaches that seem necessary. Full voice use is then resumed quickly, and the therapy program often is successful in returning the patient to normal voice production. Often, however, patients are not fully rehabilitated because an important step was neglected—the systematic exercise program to regain the balance among airflow, laryngeal muscle activity, and supraglottic placement of the tone.

A series of laryngeal muscle exercises was first described by Bertram Briess (1957, 1959). Briess suggested that for the voice to be most effective, the intrinsic muscles of the larynx must be in equilibrium. Briess's exercises concentrated on restoring the balance in the laryngeal musculature and decreasing tension of the hyperfunctioning muscles. Unfortunately, many assumptions Briess made regarding laryngeal muscle function were incorrect, and his therapy methods were not widely followed. The concept of direct exercise to strengthen voice production persisted. Barnes (1977) described a modification of Briess's work that she termed Briess Exercises. These exercises were modified and expanded by Stemple (1984) into Vocal Function Exercises. The exercise program strives to balance and strengthen the subsystems of voice production, whether the disorder is one of vocal hyperfunction or hypofunction.

The exercises are simple to teach and, when presented appropriately, seem reasonable to patients. Indeed, many patients are enthusiastic to have a concrete program, similar in concept to physical therapy, during which they may plot the progress of their return to vocal efficiency. The program begins by describing the problem to the patient, using illustrations as needed or the patient's own stroboscopic evaluation video. The patient is then taught a series of four exercises to be practiced at home, two times each, twice a day, preferably morning and evening. These exercises include the following:

The goal of the exercise is based on airflow volume. In our clinic, the goal is based on reaching 80–100 mL/s of airflow. So, if the flow volume is 4000 mL, the goal is 40–45 s. When airflow measurements are not available, the goal is equal to the longest /s/ that the patient is able to sustain. Placement of the tone should be in an extreme forward focus, almost but not quite nasal. All exercises are produced as softly as possible, but not breathy. The voice must be engaged. This is considered a warm-up exercise.

The goal is to achieve no voice breaks. The glide requires the use of all laryngeal muscles. It stretches the vocal folds and encourages a systematic, slow engagement of the cricothyroid muscles. The word knoll encourages a forward placement of the tone as well as an expanded open pharynx. The patient's lips are to be rounded, and a sympathetic vibration should be felt on the lips. (A lip trill, tongue trill, or the word whoop may also be used.) Voice breaks will typically occur in the transitions between low and high registers. When breaks occur, the patient is encouraged to continue the glide without hesitation. When the voice breaks at the top of the current range and the patient typically has more range, the glide may be continued without voice as the folds will continue to stretch. Glides improve muscular control and flexibility. This is considered a stretching exercise.

The goal is to achieve no voice breaks. The patient is instructed to feel a half-yawn in the throat throughout this exercise. By keeping the pharynx open and focusing the sympathetic vibration at the lips, the downward glide encourages a slow, systematic engagement of the thyroarytenoid muscles without the presence of a back-focused growl. In fact, no growl is permitted. (A lip trill, tongue trill, or the word boom may also be used.) This is considered a contracting exercise.

The goal is the same as for exercise 1. The -oll is produced with an open pharynx and constricted, sympathetically vibrating lips. The shape of the pharynx in respect to the lips is like an inverted megaphone. This exercise may be tailored to the patient's present vocal ability. Although the basic range of middle C (an octave lower for men) is appropriate for most voices, the exercises may be customized up or down to fit the current vocal condition or a particular voice type. Seldom, however, is the exercise shifted more than two scale steps in either direction. This is considered a low-impact adductory power exercise.

The quality of the tone is also monitored for voice breaks, wavering, and breathiness. Tone quality improves as times increase and pathologic conditions begin to resolve. All exercises are done as softly as possible. It is much more difficult to produce soft tones; therefore, the vocal subsystems will receive a better workout than if louder tones are produced. Extreme care is taken to teach the production of a forward tone that lacks tension. In addition, attention is paid to the glottal onset of the tone. The patient is asked to breathe in deeply, with attention paid to training abdominal breathing, posturing the vowel momentarily, and then initiating the exercise gesture without a forceful glottal attack or an aspirated breathy attack. It is explained to the patient that maximum phonation times increase as the efficiency of the vocal fold vibration improves. Times do not increase with improved lung capacity. (Even aerobic exercise does not improve lung capacity, but rather the efficiency of oxygen exchange with the circulatory system, thus giving the sense of more air.)

The musical notes are matched to the notes produced by an inexpensive pitch pipe that the patient purchases for use at home, or a tape recording of live voice doing the exercises may be given to the patient for home use. Many patients find the tape-recorded voice easier to match than the pitch pipe. We have found that patients who think they are “tone deaf” can often be taught to approximate the correct notes well with practice and guidance from the voice pathologist.

Finally, patients are given a chart on which to mark their sustained times, which is a means of plotting progress. Progress is monitored over time and, because of normal daily variability, patients are encouraged not to compare today with tomorrow, and so on. Rather, weekly comparisons are encouraged. The estimated time of completion for the program is 6–8 weeks. Some patients experience minor laryngeal aching for the first day or two of the program, similar to the muscle aching that might occur with any new muscular exercise. As this discomfort will soon subside, they are encouraged to continue the program through the discomfort should it occur.

When the patient has reached the predetermined therapy goal, and the voice quality and other vocal symptoms have improved, then a tapering maintenance program is recommended. Although some professional voice users choose to remain in peak vocal condition, many of our patients desire to taper the exercise program. The following systematic taper is recommended:

Each taper should last 1 week. Patients should maintain 85% of their peak time; otherwise they should move up one step in the taper until the 85% criterion is met.

Vocal Function Exercises provide a holistic voice treatment program that attends to the three major subsystems of voice production. The program appears to benefit patients with a wide range of voice disorders because it is reasonable in regard to time and effort. It is similar to other recognizable exercise programs: the concept of physical therapy for the vocal folds is understandable; progress may be easily plotted, which is inherently motivating; and it appears to balance and strengthen the relationships among airflow, laryngeal muscle activity, and supraglottic placement.