Impact of Yoga Styles on Exertion Levels: Insights from Yoga Instructors in a Cross-Sectional Study

Less than half of adults in the United States (US) meet the current Physical Activity Guidelines for Americans (PAGA) recommendation for moderate-to-vigorous level of aerobic exercise [1]. Yoga may be an effective alternative strategy to help individuals meet the exercise recommendations put forth in the PAGA. Evidence suggests that yoga promotes mental well-being [2], muscle strength, and balance [3], possibly driving this increased participation. A yoga program with higher exertion levels may enhance cardiorespiratory fitness, but it is unclear which program characteristics lead to increased exertion, especially across different yoga styles. For example, hatha yoga typically ranges from low to high intensity, with most sessions being light intensity [4]. 

Yoga Instructors (YIs) are trained to estimate clients' exertion levels, essential for exercise prescription¹ and cardiorespiratory fitness enhancement [5]. Through their training, use of subjective assessment tools, and direct observation during classes, YIs can judge the intensity of the exercises. For instance, YIs often choose more standing poses for weight loss-focused classes [6] than for relaxation-focused ones, which affects the workout intensity. Additionally, YIs practicing alongside their clients can assess the session's intensity, in line with the PAGA report's endorsement of monitoring exercise intensity through perceived exertion and physical signs [1]. This skill is especially valuable for virtual health services, where YIs' perception of client exertion is crucial for tailoring yoga programs. 

Understanding the predictors of energy expenditure across different yoga styles could offer valuable insights for healthcare providers, YIs, and patients in identifying optimal program characteristics for exertion levels. This knowledge is crucial for designing effective tele-rehabilitation or in-person yoga protocols aimed at enhancing cardiorespiratory fitness. Given the frequent practice of mixing different yoga styles during a session [7] and considering the multitude of available yoga styles [8], the overall exertion level during a complete yoga session remains unclear. Hence, this study aims to explore the relationship between yoga program characteristics across multiple styles, including mixed styles, and client exertion levels as estimated by YIs using the 10-point OMNI RPE scale.

• Participants and procedure 

YIs recruited from yoga studios and national yoga associations in the Northeastern U.S. completed this study. Inclusion criteria were: 1) currently or recently taught Yoga, 2) aged 18 years or older, and 3) proficient in reading English. We completed our cross-sectional study design using a web-based survey completed by YIs. The methods and survey procedure are described in detail elsewhere [9]. The variables used in this study came from the domain concerning yoga program characteristics. This questionnaire comprised of five domains. Questionnaire development and questions from the other domains are described in a previously published paper from this dataset [9]. All study procedures were approved by the University’s Institutional Review Board, and electronic informed consent forms were obtained from all participants. 

• Description of variables used in this study 

To identify the primary yoga style taught by YIs, they selected from a list or provided a free-text responses, similar to Cramer et al., [10] YIs also indicated if they taught multiple styles, categorized as ‘no’ for teaching only one style or ‘yes’ for incorporating another style. After identifying the primary yoga style, instructors reported the duration spent on various yoga elements like postures, breathing, meditation, dynamic postures (vinyasa), relaxation, and other practices. They also specified time spent in standing, sitting, prone, and supine positions, along with the number of breaths taken during different postures. Regarding sun salutations, instructors indicated if they performed them, how often, and at which stage during the class. The exertion level in yoga classes was gauged using YIs' estimates based on the 10-point OMNI Perceived Rate of Exertion (RPE) scale. [11] This scale is commonly used by healthcare providers and clients to monitor aerobic exercise intensity due to its simplicity and cost-effectiveness. [5] For analysis purposes, we categorized the intensity levels as low (1-4), moderate (5-7), and high (8-9). 

• Statistical analysis 

Statistical analyses were conducted using SPSS for Windows 25, with significance set at p < 0.05. Descriptive statistics involved frequency counts for nominal and categorical data and means with standard deviations for interval and ratio data. We assessed bivariate correlations using Spearman Rho, focusing on the relationship between the average intensity of exertion and yoga program characteristics like style, time spent in sitting postures, and sun salutation performance. Significant characteristics, such as dynamic sequences (vinyasa), time spent standing, and the inclusion and frequency of sun salutations, served as predictors in an ordinal logistic regression to determine their impact on the client exertion levels (CEL) as estimated by YIs.

Our response rate was 46% with a final sample size of 373 YIs who completed the survey [9]. The majority of YIs (94%) indicated that they their clients’ energy exertion rate was moderate or high (Table 1). In our sample, the most common style of yoga taught by YIs was vinyasa (44%) followed by hatha (24%).  The “Other” category included 27 other types of yoga identified by this sample of YIs.  Most YIs (87%) reported teaching more than one style of yoga in each yoga session. The two most common elements that the YIs reported using in their sessions were asana (postures) and vinyasa (dynamic sequences). The majority of participants also stated that they held most postures for 4 to 7 breaths across all positions and performed the largest amount of the class asanas in standing posture (28 Minutes). Finally, the majority of YIs (84%) claimed to practice sun salutation in their classes and on average performed this dynamic sequence 4.5 times per yoga class (SD = 4.0).

Table 1: Program characteristics that Yoga Instructors used in typical Yoga Classes.

In analyzing the relationship between yoga practices and perceived exertion, Spearman's Rho revealed that performing dynamic sequences (vinyasa) was positively correlated with exertion (r_spearman = 0.22, p = 0.001), while the frequency of sun salutation practice was negatively associated (r_spearman = -0.16, p = 0.004). Time spent in standing positions showed a moderate positive correlation with exertion (r_spearman = 0.36, p < 0.001), and the frequency of sun salutation within a session was similarly positively correlated (r_spearman = 0.27, p < 0.001). An ordinal logistic regression analysis model that included the above variables was statistically significant Χ² (4) = 29.411, p = 0.001. Time spent in standing (p = 0.007) and frequency of performing sun salutation (p = 0.006) during a yoga class added significantly to the model (Table 2). A one-unit increase in time spent in standing resulted in a 0.044 increase in the ordered log-odds in increasing CEL estimated by YIs. The ordered log-odds of CEL estimated by YIs increased 0.168 if the frequency of performing sun salutation in a class increased by one unit.

Table 2: Ordinal logistic regression analysis of average client exertion level estimated by yoga instructors with the independent variables of performing dynamic sequences, performing sun salutation, time spent in standing, and frequency of performing sun salutation.

In the present study, we found that the performance of sun salutation, practicing dynamic sequences (vinyasa), time spent in standing, and frequency of performing sun salutation in a yoga session were related to increased CEL estimated by YIs. However, only time spent in standing and frequency of performing sun salutation in a yoga session predicted increased CEL estimated by YIs. This aligns with recent evidence highlighting the elevated energy expenditure associated with vinyasa yoga and sun salutation poses [12]. Thus, if clients and health providers are looking for or YIs are designing programs to improve cardiorespiratory fitness, then they should choose yoga classes that spend greater amount of time performing standing postures and frequently perform sun salutation sequences. 

As previously reported, we found also that YIs practice multiple different styles in in the US [13]. YIs in this study reported teaching eight different yoga styles with another 27 styles classified as ‘other.’ Furthermore, like Wiese et al., [7] we found that most YIs (87%) reported using more than one yoga style in a single yoga session. These findings provide greater confidence that time-in-standing and frequency of performing sun salutation in a yoga session may predict increased CEL estimated by YIs across different yoga styles and combinations of yoga styles. This observation allows clients and health providers to ask two questions of prospective YIs to ascertain that they provide yoga at an intensity to help improve cardiorespiratory fitness: 1) what percentage of the session do you perform in standing, and 2) how often do you perform sun salutation during a yoga class? Furthermore, Larson-Meyer [4] also found that standing poses led to greater energy expenditure than performing postures in sitting. Larson-Meyer [14] further stated that certain standing poses increased energy expenditure to a moderate level intensity. However, Larson-Meyer [4] reported that these findings resulted from the practice of hatha and Bikram yoga. Our study suggests that greater standing time during a yoga session may potentially increase energy expenditure across multiple yoga styles including mixed yoga styles. 

Our results show a direct correlation between the performance of sun salutations and the CEL as estimated by YIs, with a higher frequency of sun salutation sequences leading to increased CEL. This is in line with previous studies showing that dynamic sun salutation sequences, which include various weight-bearing and bending poses [15], yield MET values over three in different yoga styles like hatha, Bikram, or ashtanga [4]. Experienced practitioners can reach 6 METs by performing four sequences [16]. This increase in CEL with more frequent sun salutations is supported by positive changes in cardiorespiratory health markers reported by other researchers [17,18]. Our findings suggest that the benefits of sun salutations on CEL are likely to extend across diverse yoga practices, not just the styles previously studied.    

The majority of the YIs in this study estimated that they taught classes where the CEL was at a moderate (35%) or high (59%) level. While practicing yoga at high intensity levels is not unheard of, [4] most exertion levels have been reported as light [4] to moderate [19]. This discrepancy might stem from the self-reported nature of the data, potential report bias, and the fact that YIs, not clients, provided the data, possibly influencing the results. Saw et al., [20] found that subjective tools can be used to monitor athletes suggesting that asking for symptoms and observation could be used by YIs to monitor clients. In this survey we found that the majority of the YIs monitor symptoms of their clients during class and will change the program based on client symptoms. The scale we used is a valid tool to use to report perceived exertion [11]. Thus, we believe that YIs can estimate clients’ exertion. 

The moderate to high CEL estimated by YIs in this study may be attributed to the nature of the yoga classes taught. A considerable proportion (44%) of the YIs specialized in vinyasa, which is known for its quick movements and moderate energy expenditure [19]. Additionally, the incorporation of dynamic sequences was found to correlate directly with higher CEL. The prevalent practice of holding postures for less than seven breaths implies frequent position changes, contributing to greater exertion. Furthermore, the fact that 84% of the YIs included sun salutations-a factor directly associated with CEL-in their sessions, and often multiple sequences of them, aligns with literature associating sun salutations with higher energy output [4,10,18]. These program characteristics likely explain the YIs' observations of moderate to high exertion levels in their classes. 

Our study has notable limitations. It lacks data on session frequency and duration, factors known to influence health outcomes [3,7]. Self-reported data may introduce bias, and the intensity reported by YIs may not align with actual client exertion. Despite this, the experienced YIs (average ~10 years) likely have a reliable sense of the intended CEL. The binary survey questions and the cross-sectional design limit the depth of our findings and preclude causal inferences. Further research should involve controlled trials, particularly with mixed yoga styles. Lastly, the results, drawn from a Northeastern U.S. sample, may not be broadly generalizable.

Yoga classes with more standing postures and sun salutation sequences are linked to higher CEL as perceived by YIs. Therefore, for those aiming to enhance cardiorespiratory fitness, selecting, or designing yoga sessions with these elements is advisable. These findings are applicable across various yoga styles, including classes that integrate multiple styles. Further research should investigate how increasing the frequency of sun salutations or time spent in standing postures affects energy expenditure biomarkers in yoga practitioners.

We gratefully acknowledge the YIs for their participation in our survey study. Without their dedication, this study would not have been possible.

The authors have no conflicts of interest to declare.

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